diff --git a/.gitattributes b/.gitattributes
index 894d27d..d231fc0 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -4,6 +4,7 @@
 /package-lock.json export-ignore
 /.gitignore export-ignore
 /.gitattributes export-ignore
+/coverage/ export-ignore
 /rollup.config.mjs export-ignore
 /tsconfig.json export-ignore
 # exclude all files in test/ from stats
@@ -11,6 +12,7 @@
 /docs/** linguist-vendored
 /tools/** linguist-vendored
 /dist/** linguist-vendored
+/coverage/** linguist-vendored
 #
 # do not replace lf by crlf
 *.css text
diff --git a/.npmignore b/.npmignore
index badbf02..c44a2fa 100644
--- a/.npmignore
+++ b/.npmignore
@@ -6,4 +6,6 @@
 /src
 /.idea
 /package-lock.json
-/node_modules
\ No newline at end of file
+/node_modules
+/coverage
+/.github
\ No newline at end of file
diff --git a/README.md b/README.md
index 3f27da3..04d1994 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+[![cov](https://tbela99.github.io/css-parser/badges/coverage.svg)](https://github.com/tbela99/css-parser/actions)
+
 # css-parser
 
 CSS parser for node and the browser
diff --git a/dist/index-umd-web.js b/dist/index-umd-web.js
index 35b4c75..a1a74a6 100644
--- a/dist/index-umd-web.js
+++ b/dist/index-umd-web.js
@@ -2241,6 +2241,53 @@
 
     const configuration = getConfig();
     const combinators = ['+', '>', '~'];
+    const notEndingWith = ['(', '['].concat(combinators);
+    function wrapNodes(previous, node, match, ast, i, nodeIndex) {
+        // @ts-ignore
+        let pSel = match.selector1.reduce(reducer, []).join(',');
+        // @ts-ignore
+        let nSel = match.selector2.reduce(reducer, []).join(',');
+        // @ts-ignore
+        const wrapper = { ...previous, chi: [], sel: match.match.reduce(reducer, []).join(',') };
+        // @ts-ignore
+        Object.defineProperty(wrapper, 'raw', {
+            enumerable: false,
+            writable: true,
+            // @ts-ignore
+            value: match.match.map(t => t.slice())
+        });
+        if (pSel == '&' || pSel === '') {
+            // @ts-ignore
+            wrapper.chi.push(...previous.chi);
+            // @ts-ignore
+            if ((nSel == '&' || nSel === '') && hasOnlyDeclarations(previous)) {
+                // @ts-ignore
+                wrapper.chi.push(...node.chi);
+            }
+            else {
+                // @ts-ignore
+                wrapper.chi.push(node);
+            }
+        }
+        else {
+            // @ts-ignore
+            wrapper.chi.push(previous, node);
+        }
+        // @ts-ignore
+        ast.chi.splice(i, 1, wrapper);
+        // @ts-ignore
+        ast.chi.splice(nodeIndex, 1);
+        // @ts-ignore
+        previous.sel = pSel;
+        // @ts-ignore
+        previous.raw = match.selector1;
+        // @ts-ignore
+        node.sel = nSel;
+        // @ts-ignore
+        node.raw = match.selector2;
+        reduceRuleSelector(wrapper);
+        return wrapper;
+    }
     function deduplicate(ast, options = {}, recursive = false) {
         // @ts-ignore
         if (('chi' in ast) && ast.chi?.length > 0) {
@@ -2277,62 +2324,21 @@
                 if (node.typ == 'Rule') {
                     reduceRuleSelector(node);
                     let wrapper;
+                    let match;
                     // @ts-ignore
                     if (options.nestingRules) {
-                        // if (node.sel == '.card>hr') {
-                        //
-                        //     console.error({idem: previous == node, previous, node});
-                        // }
                         // @ts-ignore
-                        if (previous != null) {
+                        if (previous != null && previous.typ == 'Rule') {
+                            reduceRuleSelector(previous);
                             // @ts-ignore
-                            if (node.optimized != null &&
-                                // @ts-ignore
-                                previous.optimized != null &&
-                                // @ts-ignore
-                                node.optimized.optimized.length > 0 &&
-                                // @ts-ignore
-                                previous.optimized.optimized.length > 0 &&
+                            match = matchSelectors(previous.raw, node.raw, ast.typ);
+                            // @ts-ignore
+                            if (match != null) {
                                 // @ts-ignore
-                                node.optimized.optimized[0] == previous.optimized.optimized[0]) {
+                                wrapper = wrapNodes(previous, node, match, ast, i, nodeIndex);
+                                nodeIndex = i - 1;
                                 // @ts-ignore
-                                if (hasOnlyDeclarations(previous)) {
-                                    // @ts-ignore
-                                    let pSel = reduceRawTokens(previous.optimized.selector);
-                                    if (pSel === '') {
-                                        // @ts-ignore
-                                        pSel = previous.optimized.optimized.slice(1).join('').trim();
-                                    }
-                                    // @ts-ignore
-                                    let nSel = reduceRawTokens(node.optimized.selector);
-                                    if (nSel === '') {
-                                        // @ts-ignore
-                                        nSel = node.optimized.optimized.slice(1).join('').trim();
-                                    }
-                                    // @ts-ignore
-                                    wrapper = { ...node, chi: [], sel: node.optimized.optimized[0] };
-                                    // @ts-ignore
-                                    Object.defineProperty(wrapper, 'raw', {
-                                        enumerable: false,
-                                        writable: true,
-                                        // @ts-ignore
-                                        value: [[node.optimized.optimized[0].slice()]]
-                                    });
-                                    // @ts-ignore
-                                    previous.sel = pSel === '' ? '&' : pSel; // reduceRawTokens(previous.optimized.selector);
-                                    // @ts-ignore
-                                    previous.raw = pSel === '' ? [['&']] : previous.optimized.selector.slice();
-                                    // @ts-ignore
-                                    node.sel = nSel === '' ? '&' : nSel; // reduceRawTokens(node.optimized.selector);
-                                    // @ts-ignore
-                                    node.raw = nSel === '' ? [['&']] : node.optimized.selector.slice();
-                                    // @ts-ignore
-                                    wrapper.chi.push(previous, node);
-                                    // @ts-ignore
-                                    ast.chi.splice(i, 1, wrapper);
-                                    // @ts-ignore
-                                    ast.chi.splice(nodeIndex, 1);
-                                }
+                                previous = ast.chi[nodeIndex];
                             }
                         }
                         // @ts-ignore
@@ -2342,49 +2348,26 @@
                                 // @ts-ignore
                                 const nextNode = ast.chi[i];
                                 // @ts-ignore
-                                if (nextNode.typ != 'Rule' || nextNode.raw == null) {
+                                if (nextNode.typ != 'Rule') {
+                                    // i--;
+                                    // previous = wrapper;
+                                    // nodeIndex = i;
                                     break;
                                 }
                                 reduceRuleSelector(nextNode);
                                 // @ts-ignore
-                                if (nextNode.raw.length != 1 || !eq(wrapper.raw[0], nextNode.raw[0].slice(0, wrapper.raw[0].length))) {
-                                    break;
-                                }
-                                // @ts-ignore
-                                nextNode.raw[0].splice(0, wrapper.raw[0].length);
-                                // @ts-ignore
-                                trimRawToken(nextNode.raw[0]);
+                                match = matchSelectors(wrapper.raw, nextNode.raw, ast.typ);
                                 // @ts-ignore
-                                if (nextNode.raw[0].length == 0 ||
-                                    // @ts-ignore
-                                    (nextNode.raw.length == 1 && nextNode.raw[0] == '&')) {
-                                    if (hasOnlyDeclarations(wrapper)) {
-                                        // @ts-ignore
-                                        wrapper.chi.push(...nextNode.chi);
-                                        // @ts-ignore
-                                        ast.chi.splice(i, 1);
-                                        continue;
-                                    }
-                                    else {
-                                        // @ts-ignore
-                                        nextNode.raw[0].push('&');
-                                    }
+                                if (match == null) {
+                                    break;
                                 }
                                 // @ts-ignore
-                                nextNode.sel = nextNode.raw.reduce((acc, curr) => {
-                                    acc.push(curr.join(''));
-                                    return acc;
-                                }, []).join(',');
-                                // @ts-ignore
-                                wrapper.chi.push(nextNode);
-                                // @ts-ignore
-                                ast.chi.splice(i, 1);
-                                node = wrapper;
+                                wrapper = wrapNodes(wrapper, nextNode, match, ast, i, nodeIndex);
                             }
-                            deduplicate(wrapper, options, recursive);
-                            nodeIndex = i;
+                            nodeIndex = --i;
                             // @ts-ignore
-                            previous = ast.chi[i];
+                            previous = ast.chi[nodeIndex];
+                            deduplicate(wrapper, options, recursive);
                             continue;
                         }
                         // @ts-ignore
@@ -2403,7 +2386,7 @@
                                 value: [[node.optimized.optimized[0]]]
                             });
                             // @ts-ignore
-                            node.sel = reduceRawTokens(node.optimized.selector);
+                            node.sel = node.optimized.selector.reduce(reducer, []).join(',');
                             // @ts-ignore
                             node.raw = node.optimized.selector.slice();
                             // @ts-ignore
@@ -2413,6 +2396,34 @@
                             node = wrapper;
                         }
                     }
+                    // @ts-ignore
+                    else if (node.optimized?.match) {
+                        let wrap = true;
+                        // @ts-ignore
+                        const selector = node.optimized.selector.reduce((acc, curr) => {
+                            if (curr[0] == '&') {
+                                if (curr[1] == ' ') {
+                                    curr.splice(0, 2);
+                                }
+                                else {
+                                    if (ast.typ != 'Rule' && combinators.includes(curr[1])) {
+                                        wrap = false;
+                                    }
+                                    else {
+                                        curr.splice(0, 1);
+                                    }
+                                }
+                            }
+                            else if (combinators.includes(curr[0])) {
+                                curr.unshift('&');
+                            }
+                            // @ts-ignore
+                            acc.push(curr.map(t => t.replaceAll('&', node.optimized.optimized[0])).join(''));
+                            return acc;
+                        }, []);
+                        // @ts-ignore
+                        node.sel = (wrap ? node.optimized.optimized[0] : '') + `:is(${selector.join(',')})`;
+                    }
                 }
                 // @ts-ignore
                 if (previous != null && 'chi' in previous && ('chi' in node)) {
@@ -2441,6 +2452,7 @@
                                 ast.chi.splice(nodeIndex, 1);
                                 // @ts-ignore
                                 if (hasDeclaration(node)) {
+                                    // @ts-ignore
                                     deduplicateRule(node);
                                 }
                                 else {
@@ -2485,6 +2497,7 @@
                     if (recursive && previous != node) {
                         // @ts-ignore
                         if (hasDeclaration(previous)) {
+                            // @ts-ignore
                             deduplicateRule(previous);
                         }
                         else {
@@ -2582,31 +2595,40 @@
         ast.chi = children.concat(ast.chi?.slice(k));
         return ast;
     }
-    function reduceRawTokens(raw) {
-        return raw.reduce((acc, curr) => {
-            acc.push(curr.join(''));
-            return acc;
-        }, []).join(',');
-    }
-    function trimRawToken(raw) {
-        while (raw.length > 0) {
-            if (raw[0] == ' ') {
-                raw.shift();
-                continue;
-            }
-            break;
-        }
-    }
     function splitRule(buffer) {
-        const result = [];
+        const result = [[]];
         let str = '';
         for (let i = 0; i < buffer.length; i++) {
             let chr = buffer.charAt(i);
+            if (isWhiteSpace(chr.charCodeAt(0))) {
+                let k = i;
+                while (k + 1 < buffer.length) {
+                    if (isWhiteSpace(buffer[k + 1].charCodeAt(0))) {
+                        k++;
+                        continue;
+                    }
+                    break;
+                }
+                if (str !== '') {
+                    // @ts-ignore
+                    result.at(-1).push(str);
+                    str = '';
+                }
+                // @ts-ignore
+                if (result.at(-1).length > 0) {
+                    // @ts-ignore
+                    result.at(-1).push(' ');
+                }
+                i = k;
+                continue;
+            }
             if (chr == ',') {
                 if (str !== '') {
-                    result.push(str);
+                    // @ts-ignore
+                    result.at(-1).push(str);
                     str = '';
                 }
+                result.push([]);
                 continue;
             }
             str += chr;
@@ -2656,41 +2678,45 @@
             }
         }
         if (str !== '') {
-            result.push(str);
+            // @ts-ignore
+            result.at(-1).push(str);
         }
         return result;
     }
     function reduceRuleSelector(node) {
+        if (node.raw == null) {
+            Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: splitRule(node.sel) });
+        }
         // @ts-ignore
-        if (node.raw != null) {
-            // @ts-ignore
-            let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
-                acc.push(curr.slice());
-                return acc;
-            }, []));
-            if (optimized != null) {
-                Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
-            }
-            if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
-                const raw = [
-                    [
-                        optimized.optimized[0], ':is('
-                    ].concat(optimized.selector.reduce((acc, curr) => {
-                        if (acc.length > 0) {
-                            acc.push(',');
-                        }
-                        acc.push(...curr);
-                        return acc;
-                    }, [])).concat(')')
-                ];
-                const sel = raw[0].join('');
-                if (sel.length < node.sel.length) {
-                    node.sel = sel;
-                    // node.raw = raw;
-                    Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
-                }
+        // if (node.raw != null) {
+        // @ts-ignore
+        let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
+            acc.push(curr.slice());
+            return acc;
+        }, []));
+        if (optimized != null) {
+            Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
+        }
+        if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
+            const raw = [
+                [
+                    optimized.optimized[0], ':is('
+                ].concat(optimized.selector.reduce((acc, curr) => {
+                    if (acc.length > 0) {
+                        acc.push(',');
+                    }
+                    acc.push(...curr);
+                    return acc;
+                }, [])).concat(')')
+            ];
+            const sel = raw[0].join('');
+            if (sel.length < node.sel.length) {
+                node.sel = sel;
+                // node.raw = raw;
+                Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
             }
         }
+        // }
     }
     function diff(n1, n2, options = {}) {
         let node1 = n1;
@@ -2711,25 +2737,25 @@
         // @ts-ignore
         const raw1 = node1.raw;
         // @ts-ignore
-        const optimized1 = node1.optimized;
+        // const optimized1 = node1.optimized;
         // @ts-ignore
         const raw2 = node2.raw;
         // @ts-ignore
-        const optimized2 = node2.optimized;
+        // const optimized2 = node2.optimized;
         node1 = { ...node1, chi: node1.chi.slice() };
         node2 = { ...node2, chi: node2.chi.slice() };
         if (raw1 != null) {
             Object.defineProperty(node1, 'raw', { enumerable: false, writable: true, value: raw1 });
         }
-        if (optimized1 != null) {
-            Object.defineProperty(node1, 'optimized', { enumerable: false, writable: true, value: optimized1 });
-        }
+        // if (optimized1 != null) {
+        //     Object.defineProperty(node1, 'optimized', {enumerable: false, writable: true, value: optimized1});
+        // }
         if (raw2 != null) {
             Object.defineProperty(node2, 'raw', { enumerable: false, writable: true, value: raw2 });
         }
-        if (optimized2 != null) {
-            Object.defineProperty(node2, 'optimized', { enumerable: false, writable: true, value: optimized2 });
-        }
+        // if (optimized2 != null) {
+        //     Object.defineProperty(node2, 'optimized', {enumerable: false, writable: true, value: optimized2});
+        // }
         const intersect = [];
         while (i--) {
             if (node1.chi[i].typ == 'Comment') {
@@ -2757,7 +2783,7 @@
         const result = (intersect.length == 0 ? null : {
             ...node1,
             // @ts-ignore
-            sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(),
+            sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(','),
             chi: intersect.reverse()
         });
         if (result == null || [n1, n2].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0) <= [node1, node2, result].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0)) {
@@ -2766,6 +2792,167 @@
         }
         return { result, node1: exchanged ? node2 : node1, node2: exchanged ? node2 : node2 };
     }
+    function matchSelectors(selector1, selector2, parentType) {
+        let match = [[]];
+        const j = Math.min(selector1.reduce((acc, curr) => Math.min(acc, curr.length), selector1.length > 0 ? selector1[0].length : 0), selector2.reduce((acc, curr) => Math.min(acc, curr.length), selector2.length > 0 ? selector2[0].length : 0));
+        let i = 0;
+        let k;
+        let l;
+        let token;
+        let matching = true;
+        let matchFunction = 0;
+        let inAttr = 0;
+        for (; i < j; i++) {
+            k = 0;
+            token = selector1[0][i];
+            for (; k < selector1.length; k++) {
+                if (selector1[k][i] != token) {
+                    matching = false;
+                    break;
+                }
+            }
+            if (matching) {
+                l = 0;
+                for (; l < selector2.length; l++) {
+                    if (selector2[l][i] != token) {
+                        matching = false;
+                        break;
+                    }
+                }
+            }
+            if (!matching) {
+                break;
+            }
+            if (token == ',') {
+                match.push([]);
+            }
+            else {
+                if (token.endsWith('(')) {
+                    matchFunction++;
+                }
+                if (token.endsWith('[')) {
+                    inAttr++;
+                }
+                else if (token == ')') {
+                    matchFunction--;
+                }
+                else if (token == ']') {
+                    inAttr--;
+                }
+                match.at(-1).push(token);
+            }
+        }
+        // invalid function
+        if (matchFunction != 0 || inAttr != 0) {
+            return null;
+        }
+        if (parentType != 'Rule') {
+            for (const part of match) {
+                if (part.length > 0 && combinators.includes(part[0].charAt(0))) {
+                    return null;
+                }
+            }
+        }
+        if (match.length > 1) {
+            console.error(`unsupported multilevel matching`);
+            console.error({ match, selector1, selector2 });
+            return null;
+        }
+        for (const part of match) {
+            while (part.length > 0) {
+                const token = part.at(-1);
+                if (token == ' ' || combinators.includes(token) || notEndingWith.includes(token.at(-1))) {
+                    part.pop();
+                    continue;
+                }
+                break;
+            }
+        }
+        if (match.every(t => t.length == 0)) {
+            return null;
+        }
+        if (eq([['&']], match)) {
+            return null;
+        }
+        function reduce(acc, curr) {
+            if (acc === null) {
+                return null;
+            }
+            let hasCompoundSelector = true;
+            curr = curr.slice(match[0].length);
+            while (curr.length > 0) {
+                if (curr[0] == ' ') {
+                    hasCompoundSelector = false;
+                    curr.unshift('&');
+                    continue;
+                }
+                break;
+            }
+            // invalid function match
+            if (curr.length > 0 && curr[0].endsWith('(') && curr.at(-1) != ')') {
+                return null;
+            }
+            if (curr.length == 1 && combinators.includes(curr[0].charAt(0))) {
+                return null;
+            }
+            if (hasCompoundSelector && curr.length > 0) {
+                hasCompoundSelector = !['&'].concat(combinators).includes(curr[0].charAt(0));
+            }
+            if (curr[0] == ':is(') {
+                let inFunction = 0;
+                let canReduce = true;
+                const isCompound = curr.reduce((acc, token, index) => {
+                    if (index == 0) {
+                        inFunction++;
+                        canReduce = curr[1] == '&';
+                    }
+                    else if (token.endsWith('(')) {
+                        if (inFunction == 0) {
+                            canReduce = false;
+                        }
+                        inFunction++;
+                    }
+                    else if (token == ')') {
+                        inFunction--;
+                    }
+                    else if (token == ',') {
+                        if (!canReduce) {
+                            canReduce = curr[index + 1] == '&';
+                        }
+                        acc.push([]);
+                    }
+                    else
+                        acc.at(-1)?.push(token);
+                    return acc;
+                }, [[]]);
+                if (inFunction > 0) {
+                    canReduce = false;
+                }
+                if (canReduce) {
+                    curr = isCompound.reduce((acc, curr) => {
+                        if (acc.length > 0) {
+                            acc.push(',');
+                        }
+                        acc.push(...curr);
+                        return acc;
+                    }, []);
+                }
+            }
+            // @todo: check hasCompoundSelector && curr[0] == '&' && curr[1] == ' '
+            acc.push(match.length == 0 ? ['&'] : (hasCompoundSelector && curr[0] != '&' && (curr.length == 0 || !combinators.includes(curr[0].charAt(0))) ? ['&'].concat(curr) : curr));
+            return acc;
+        }
+        // @ts-ignore
+        selector1 = selector1.reduce(reduce, []);
+        // @ts-ignore
+        selector2 = selector2.reduce(reduce, []);
+        return selector1 == null || selector2 == null ? null : {
+            eq: eq(selector1, selector2),
+            match,
+            selector1,
+            selector2
+        };
+    }
     function reduceSelector(selector) {
         if (selector.length == 0) {
             return null;
@@ -2789,49 +2976,75 @@
             }
             optimized.push(item);
         }
+        while (optimized.length > 0) {
+            const last = optimized.at(-1);
+            if ((last == ' ' || combinators.includes(last))) {
+                optimized.pop();
+                continue;
+            }
+            break;
+        }
         selector.forEach((selector) => selector.splice(0, optimized.length));
         // combinator
         if (combinators.includes(optimized.at(-1))) {
             const combinator = optimized.pop();
             selector.forEach(selector => selector.unshift(combinator));
         }
-        if (optimized.at(-1) == ' ') {
-            optimized.pop();
-        }
         let reducible = optimized.length == 1;
+        if (optimized[0] == '&' && optimized[1] == ' ') {
+            optimized.splice(0, 2);
+        }
         if (optimized.length == 0 ||
-            optimized[0].charAt(0) == '&' ||
-            selector.length == 1) {
+            (optimized[0].charAt(0) == '&' ||
+                selector.length == 1)) {
             return {
                 match: false,
                 optimized,
-                selector,
-                reducible: selector.length > 1 && selector.every((selector) => !['>', '+', '~'].includes(selector[0]))
+                selector: selector.map(selector => selector[0] == '&' && selector[1] == ' ' ? selector.slice(2) : selector),
+                reducible: selector.length > 1 && selector.every((selector) => !combinators.includes(selector[0]))
             };
         }
         return {
             match: true,
             optimized,
             selector: selector.reduce((acc, curr) => {
+                let hasCompound = true;
+                if (hasCompound && curr.length > 0) {
+                    hasCompound = !['&'].concat(combinators).includes(curr[0].charAt(0));
+                }
                 // @ts-ignore
-                if (curr.length > 0 && curr[0] == ' ') {
-                    curr.shift();
+                if (hasCompound && curr[0] == ' ') {
+                    hasCompound = false;
+                    curr.unshift('&');
                 }
                 if (curr.length == 0) {
                     curr.push('&');
+                    hasCompound = false;
                 }
                 if (reducible) {
                     const chr = curr[0].charAt(0);
                     // @ts-ignore
                     reducible = chr == '.' || chr == ':' || isIdentStart(chr.codePointAt(0));
                 }
-                acc.push(curr);
+                acc.push(hasCompound ? ['&'].concat(curr) : curr);
                 return acc;
             }, []),
             reducible: selector.every((selector) => !['>', '+', '~', '&'].includes(selector[0]))
         };
     }
-    function reducer(acc, curr) {
+    function reducer(acc, curr, index, array) {
+        // trim :is()
+        if (array.length == 1 && array[0][0] == ':is(' && array[0].at(-1) == ')') {
+            curr = curr.slice(1, -1);
+        }
+        if (curr[0] == '&') {
+            if (curr[1] == ' ') {
+                curr.splice(0, 2);
+            }
+            else if (combinators.includes(curr[1])) {
+                curr.splice(0, 1);
+            }
+        }
         acc.push(curr.join(''));
         return acc;
     }
@@ -3573,13 +3786,13 @@
                     buffer = value;
                     break;
                 case '>':
-                    if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
-                        tokens.pop();
-                    }
                     if (buffer !== '') {
                         pushToken(getType(buffer));
                         buffer = '';
                     }
+                    if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
+                        tokens.pop();
+                    }
                     pushToken({ typ: 'Gt' });
                     consumeWhiteSpace();
                     break;
@@ -4018,7 +4231,7 @@
         yield { node, parent, root };
         if ('chi' in node) {
             for (const child of node.chi) {
-                yield* doWalk(child, node, (root == null ? node : root));
+                yield* doWalk(child, node, (root ?? node));
             }
         }
     }
diff --git a/dist/index.cjs b/dist/index.cjs
index afe6ade..034515e 100644
--- a/dist/index.cjs
+++ b/dist/index.cjs
@@ -2239,6 +2239,53 @@ class PropertyList {
 
 const configuration = getConfig();
 const combinators = ['+', '>', '~'];
+const notEndingWith = ['(', '['].concat(combinators);
+function wrapNodes(previous, node, match, ast, i, nodeIndex) {
+    // @ts-ignore
+    let pSel = match.selector1.reduce(reducer, []).join(',');
+    // @ts-ignore
+    let nSel = match.selector2.reduce(reducer, []).join(',');
+    // @ts-ignore
+    const wrapper = { ...previous, chi: [], sel: match.match.reduce(reducer, []).join(',') };
+    // @ts-ignore
+    Object.defineProperty(wrapper, 'raw', {
+        enumerable: false,
+        writable: true,
+        // @ts-ignore
+        value: match.match.map(t => t.slice())
+    });
+    if (pSel == '&' || pSel === '') {
+        // @ts-ignore
+        wrapper.chi.push(...previous.chi);
+        // @ts-ignore
+        if ((nSel == '&' || nSel === '') && hasOnlyDeclarations(previous)) {
+            // @ts-ignore
+            wrapper.chi.push(...node.chi);
+        }
+        else {
+            // @ts-ignore
+            wrapper.chi.push(node);
+        }
+    }
+    else {
+        // @ts-ignore
+        wrapper.chi.push(previous, node);
+    }
+    // @ts-ignore
+    ast.chi.splice(i, 1, wrapper);
+    // @ts-ignore
+    ast.chi.splice(nodeIndex, 1);
+    // @ts-ignore
+    previous.sel = pSel;
+    // @ts-ignore
+    previous.raw = match.selector1;
+    // @ts-ignore
+    node.sel = nSel;
+    // @ts-ignore
+    node.raw = match.selector2;
+    reduceRuleSelector(wrapper);
+    return wrapper;
+}
 function deduplicate(ast, options = {}, recursive = false) {
     // @ts-ignore
     if (('chi' in ast) && ast.chi?.length > 0) {
@@ -2275,62 +2322,21 @@ function deduplicate(ast, options = {}, recursive = false) {
             if (node.typ == 'Rule') {
                 reduceRuleSelector(node);
                 let wrapper;
+                let match;
                 // @ts-ignore
                 if (options.nestingRules) {
-                    // if (node.sel == '.card>hr') {
-                    //
-                    //     console.error({idem: previous == node, previous, node});
-                    // }
                     // @ts-ignore
-                    if (previous != null) {
+                    if (previous != null && previous.typ == 'Rule') {
+                        reduceRuleSelector(previous);
                         // @ts-ignore
-                        if (node.optimized != null &&
-                            // @ts-ignore
-                            previous.optimized != null &&
-                            // @ts-ignore
-                            node.optimized.optimized.length > 0 &&
-                            // @ts-ignore
-                            previous.optimized.optimized.length > 0 &&
+                        match = matchSelectors(previous.raw, node.raw, ast.typ);
+                        // @ts-ignore
+                        if (match != null) {
                             // @ts-ignore
-                            node.optimized.optimized[0] == previous.optimized.optimized[0]) {
+                            wrapper = wrapNodes(previous, node, match, ast, i, nodeIndex);
+                            nodeIndex = i - 1;
                             // @ts-ignore
-                            if (hasOnlyDeclarations(previous)) {
-                                // @ts-ignore
-                                let pSel = reduceRawTokens(previous.optimized.selector);
-                                if (pSel === '') {
-                                    // @ts-ignore
-                                    pSel = previous.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                let nSel = reduceRawTokens(node.optimized.selector);
-                                if (nSel === '') {
-                                    // @ts-ignore
-                                    nSel = node.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                wrapper = { ...node, chi: [], sel: node.optimized.optimized[0] };
-                                // @ts-ignore
-                                Object.defineProperty(wrapper, 'raw', {
-                                    enumerable: false,
-                                    writable: true,
-                                    // @ts-ignore
-                                    value: [[node.optimized.optimized[0].slice()]]
-                                });
-                                // @ts-ignore
-                                previous.sel = pSel === '' ? '&' : pSel; // reduceRawTokens(previous.optimized.selector);
-                                // @ts-ignore
-                                previous.raw = pSel === '' ? [['&']] : previous.optimized.selector.slice();
-                                // @ts-ignore
-                                node.sel = nSel === '' ? '&' : nSel; // reduceRawTokens(node.optimized.selector);
-                                // @ts-ignore
-                                node.raw = nSel === '' ? [['&']] : node.optimized.selector.slice();
-                                // @ts-ignore
-                                wrapper.chi.push(previous, node);
-                                // @ts-ignore
-                                ast.chi.splice(i, 1, wrapper);
-                                // @ts-ignore
-                                ast.chi.splice(nodeIndex, 1);
-                            }
+                            previous = ast.chi[nodeIndex];
                         }
                     }
                     // @ts-ignore
@@ -2340,49 +2346,26 @@ function deduplicate(ast, options = {}, recursive = false) {
                             // @ts-ignore
                             const nextNode = ast.chi[i];
                             // @ts-ignore
-                            if (nextNode.typ != 'Rule' || nextNode.raw == null) {
+                            if (nextNode.typ != 'Rule') {
+                                // i--;
+                                // previous = wrapper;
+                                // nodeIndex = i;
                                 break;
                             }
                             reduceRuleSelector(nextNode);
                             // @ts-ignore
-                            if (nextNode.raw.length != 1 || !eq(wrapper.raw[0], nextNode.raw[0].slice(0, wrapper.raw[0].length))) {
-                                break;
-                            }
-                            // @ts-ignore
-                            nextNode.raw[0].splice(0, wrapper.raw[0].length);
-                            // @ts-ignore
-                            trimRawToken(nextNode.raw[0]);
+                            match = matchSelectors(wrapper.raw, nextNode.raw, ast.typ);
                             // @ts-ignore
-                            if (nextNode.raw[0].length == 0 ||
-                                // @ts-ignore
-                                (nextNode.raw.length == 1 && nextNode.raw[0] == '&')) {
-                                if (hasOnlyDeclarations(wrapper)) {
-                                    // @ts-ignore
-                                    wrapper.chi.push(...nextNode.chi);
-                                    // @ts-ignore
-                                    ast.chi.splice(i, 1);
-                                    continue;
-                                }
-                                else {
-                                    // @ts-ignore
-                                    nextNode.raw[0].push('&');
-                                }
+                            if (match == null) {
+                                break;
                             }
                             // @ts-ignore
-                            nextNode.sel = nextNode.raw.reduce((acc, curr) => {
-                                acc.push(curr.join(''));
-                                return acc;
-                            }, []).join(',');
-                            // @ts-ignore
-                            wrapper.chi.push(nextNode);
-                            // @ts-ignore
-                            ast.chi.splice(i, 1);
-                            node = wrapper;
+                            wrapper = wrapNodes(wrapper, nextNode, match, ast, i, nodeIndex);
                         }
-                        deduplicate(wrapper, options, recursive);
-                        nodeIndex = i;
+                        nodeIndex = --i;
                         // @ts-ignore
-                        previous = ast.chi[i];
+                        previous = ast.chi[nodeIndex];
+                        deduplicate(wrapper, options, recursive);
                         continue;
                     }
                     // @ts-ignore
@@ -2401,7 +2384,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                             value: [[node.optimized.optimized[0]]]
                         });
                         // @ts-ignore
-                        node.sel = reduceRawTokens(node.optimized.selector);
+                        node.sel = node.optimized.selector.reduce(reducer, []).join(',');
                         // @ts-ignore
                         node.raw = node.optimized.selector.slice();
                         // @ts-ignore
@@ -2411,6 +2394,34 @@ function deduplicate(ast, options = {}, recursive = false) {
                         node = wrapper;
                     }
                 }
+                // @ts-ignore
+                else if (node.optimized?.match) {
+                    let wrap = true;
+                    // @ts-ignore
+                    const selector = node.optimized.selector.reduce((acc, curr) => {
+                        if (curr[0] == '&') {
+                            if (curr[1] == ' ') {
+                                curr.splice(0, 2);
+                            }
+                            else {
+                                if (ast.typ != 'Rule' && combinators.includes(curr[1])) {
+                                    wrap = false;
+                                }
+                                else {
+                                    curr.splice(0, 1);
+                                }
+                            }
+                        }
+                        else if (combinators.includes(curr[0])) {
+                            curr.unshift('&');
+                        }
+                        // @ts-ignore
+                        acc.push(curr.map(t => t.replaceAll('&', node.optimized.optimized[0])).join(''));
+                        return acc;
+                    }, []);
+                    // @ts-ignore
+                    node.sel = (wrap ? node.optimized.optimized[0] : '') + `:is(${selector.join(',')})`;
+                }
             }
             // @ts-ignore
             if (previous != null && 'chi' in previous && ('chi' in node)) {
@@ -2439,6 +2450,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                             ast.chi.splice(nodeIndex, 1);
                             // @ts-ignore
                             if (hasDeclaration(node)) {
+                                // @ts-ignore
                                 deduplicateRule(node);
                             }
                             else {
@@ -2483,6 +2495,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                 if (recursive && previous != node) {
                     // @ts-ignore
                     if (hasDeclaration(previous)) {
+                        // @ts-ignore
                         deduplicateRule(previous);
                     }
                     else {
@@ -2580,31 +2593,40 @@ function deduplicateRule(ast) {
     ast.chi = children.concat(ast.chi?.slice(k));
     return ast;
 }
-function reduceRawTokens(raw) {
-    return raw.reduce((acc, curr) => {
-        acc.push(curr.join(''));
-        return acc;
-    }, []).join(',');
-}
-function trimRawToken(raw) {
-    while (raw.length > 0) {
-        if (raw[0] == ' ') {
-            raw.shift();
-            continue;
-        }
-        break;
-    }
-}
 function splitRule(buffer) {
-    const result = [];
+    const result = [[]];
     let str = '';
     for (let i = 0; i < buffer.length; i++) {
         let chr = buffer.charAt(i);
+        if (isWhiteSpace(chr.charCodeAt(0))) {
+            let k = i;
+            while (k + 1 < buffer.length) {
+                if (isWhiteSpace(buffer[k + 1].charCodeAt(0))) {
+                    k++;
+                    continue;
+                }
+                break;
+            }
+            if (str !== '') {
+                // @ts-ignore
+                result.at(-1).push(str);
+                str = '';
+            }
+            // @ts-ignore
+            if (result.at(-1).length > 0) {
+                // @ts-ignore
+                result.at(-1).push(' ');
+            }
+            i = k;
+            continue;
+        }
         if (chr == ',') {
             if (str !== '') {
-                result.push(str);
+                // @ts-ignore
+                result.at(-1).push(str);
                 str = '';
             }
+            result.push([]);
             continue;
         }
         str += chr;
@@ -2654,41 +2676,45 @@ function splitRule(buffer) {
         }
     }
     if (str !== '') {
-        result.push(str);
+        // @ts-ignore
+        result.at(-1).push(str);
     }
     return result;
 }
 function reduceRuleSelector(node) {
+    if (node.raw == null) {
+        Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: splitRule(node.sel) });
+    }
     // @ts-ignore
-    if (node.raw != null) {
-        // @ts-ignore
-        let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
-            acc.push(curr.slice());
-            return acc;
-        }, []));
-        if (optimized != null) {
-            Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
-        }
-        if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
-            const raw = [
-                [
-                    optimized.optimized[0], ':is('
-                ].concat(optimized.selector.reduce((acc, curr) => {
-                    if (acc.length > 0) {
-                        acc.push(',');
-                    }
-                    acc.push(...curr);
-                    return acc;
-                }, [])).concat(')')
-            ];
-            const sel = raw[0].join('');
-            if (sel.length < node.sel.length) {
-                node.sel = sel;
-                // node.raw = raw;
-                Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
-            }
+    // if (node.raw != null) {
+    // @ts-ignore
+    let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
+        acc.push(curr.slice());
+        return acc;
+    }, []));
+    if (optimized != null) {
+        Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
+    }
+    if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
+        const raw = [
+            [
+                optimized.optimized[0], ':is('
+            ].concat(optimized.selector.reduce((acc, curr) => {
+                if (acc.length > 0) {
+                    acc.push(',');
+                }
+                acc.push(...curr);
+                return acc;
+            }, [])).concat(')')
+        ];
+        const sel = raw[0].join('');
+        if (sel.length < node.sel.length) {
+            node.sel = sel;
+            // node.raw = raw;
+            Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
         }
     }
+    // }
 }
 function diff(n1, n2, options = {}) {
     let node1 = n1;
@@ -2709,25 +2735,25 @@ function diff(n1, n2, options = {}) {
     // @ts-ignore
     const raw1 = node1.raw;
     // @ts-ignore
-    const optimized1 = node1.optimized;
+    // const optimized1 = node1.optimized;
     // @ts-ignore
     const raw2 = node2.raw;
     // @ts-ignore
-    const optimized2 = node2.optimized;
+    // const optimized2 = node2.optimized;
     node1 = { ...node1, chi: node1.chi.slice() };
     node2 = { ...node2, chi: node2.chi.slice() };
     if (raw1 != null) {
         Object.defineProperty(node1, 'raw', { enumerable: false, writable: true, value: raw1 });
     }
-    if (optimized1 != null) {
-        Object.defineProperty(node1, 'optimized', { enumerable: false, writable: true, value: optimized1 });
-    }
+    // if (optimized1 != null) {
+    //     Object.defineProperty(node1, 'optimized', {enumerable: false, writable: true, value: optimized1});
+    // }
     if (raw2 != null) {
         Object.defineProperty(node2, 'raw', { enumerable: false, writable: true, value: raw2 });
     }
-    if (optimized2 != null) {
-        Object.defineProperty(node2, 'optimized', { enumerable: false, writable: true, value: optimized2 });
-    }
+    // if (optimized2 != null) {
+    //     Object.defineProperty(node2, 'optimized', {enumerable: false, writable: true, value: optimized2});
+    // }
     const intersect = [];
     while (i--) {
         if (node1.chi[i].typ == 'Comment') {
@@ -2755,7 +2781,7 @@ function diff(n1, n2, options = {}) {
     const result = (intersect.length == 0 ? null : {
         ...node1,
         // @ts-ignore
-        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(),
+        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(','),
         chi: intersect.reverse()
     });
     if (result == null || [n1, n2].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0) <= [node1, node2, result].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0)) {
@@ -2764,6 +2790,167 @@ function diff(n1, n2, options = {}) {
     }
     return { result, node1: exchanged ? node2 : node1, node2: exchanged ? node2 : node2 };
 }
+function matchSelectors(selector1, selector2, parentType) {
+    let match = [[]];
+    const j = Math.min(selector1.reduce((acc, curr) => Math.min(acc, curr.length), selector1.length > 0 ? selector1[0].length : 0), selector2.reduce((acc, curr) => Math.min(acc, curr.length), selector2.length > 0 ? selector2[0].length : 0));
+    let i = 0;
+    let k;
+    let l;
+    let token;
+    let matching = true;
+    let matchFunction = 0;
+    let inAttr = 0;
+    for (; i < j; i++) {
+        k = 0;
+        token = selector1[0][i];
+        for (; k < selector1.length; k++) {
+            if (selector1[k][i] != token) {
+                matching = false;
+                break;
+            }
+        }
+        if (matching) {
+            l = 0;
+            for (; l < selector2.length; l++) {
+                if (selector2[l][i] != token) {
+                    matching = false;
+                    break;
+                }
+            }
+        }
+        if (!matching) {
+            break;
+        }
+        if (token == ',') {
+            match.push([]);
+        }
+        else {
+            if (token.endsWith('(')) {
+                matchFunction++;
+            }
+            if (token.endsWith('[')) {
+                inAttr++;
+            }
+            else if (token == ')') {
+                matchFunction--;
+            }
+            else if (token == ']') {
+                inAttr--;
+            }
+            match.at(-1).push(token);
+        }
+    }
+    // invalid function
+    if (matchFunction != 0 || inAttr != 0) {
+        return null;
+    }
+    if (parentType != 'Rule') {
+        for (const part of match) {
+            if (part.length > 0 && combinators.includes(part[0].charAt(0))) {
+                return null;
+            }
+        }
+    }
+    if (match.length > 1) {
+        console.error(`unsupported multilevel matching`);
+        console.error({ match, selector1, selector2 });
+        return null;
+    }
+    for (const part of match) {
+        while (part.length > 0) {
+            const token = part.at(-1);
+            if (token == ' ' || combinators.includes(token) || notEndingWith.includes(token.at(-1))) {
+                part.pop();
+                continue;
+            }
+            break;
+        }
+    }
+    if (match.every(t => t.length == 0)) {
+        return null;
+    }
+    if (eq([['&']], match)) {
+        return null;
+    }
+    function reduce(acc, curr) {
+        if (acc === null) {
+            return null;
+        }
+        let hasCompoundSelector = true;
+        curr = curr.slice(match[0].length);
+        while (curr.length > 0) {
+            if (curr[0] == ' ') {
+                hasCompoundSelector = false;
+                curr.unshift('&');
+                continue;
+            }
+            break;
+        }
+        // invalid function match
+        if (curr.length > 0 && curr[0].endsWith('(') && curr.at(-1) != ')') {
+            return null;
+        }
+        if (curr.length == 1 && combinators.includes(curr[0].charAt(0))) {
+            return null;
+        }
+        if (hasCompoundSelector && curr.length > 0) {
+            hasCompoundSelector = !['&'].concat(combinators).includes(curr[0].charAt(0));
+        }
+        if (curr[0] == ':is(') {
+            let inFunction = 0;
+            let canReduce = true;
+            const isCompound = curr.reduce((acc, token, index) => {
+                if (index == 0) {
+                    inFunction++;
+                    canReduce = curr[1] == '&';
+                }
+                else if (token.endsWith('(')) {
+                    if (inFunction == 0) {
+                        canReduce = false;
+                    }
+                    inFunction++;
+                }
+                else if (token == ')') {
+                    inFunction--;
+                }
+                else if (token == ',') {
+                    if (!canReduce) {
+                        canReduce = curr[index + 1] == '&';
+                    }
+                    acc.push([]);
+                }
+                else
+                    acc.at(-1)?.push(token);
+                return acc;
+            }, [[]]);
+            if (inFunction > 0) {
+                canReduce = false;
+            }
+            if (canReduce) {
+                curr = isCompound.reduce((acc, curr) => {
+                    if (acc.length > 0) {
+                        acc.push(',');
+                    }
+                    acc.push(...curr);
+                    return acc;
+                }, []);
+            }
+        }
+        // @todo: check hasCompoundSelector && curr[0] == '&' && curr[1] == ' '
+        acc.push(match.length == 0 ? ['&'] : (hasCompoundSelector && curr[0] != '&' && (curr.length == 0 || !combinators.includes(curr[0].charAt(0))) ? ['&'].concat(curr) : curr));
+        return acc;
+    }
+    // @ts-ignore
+    selector1 = selector1.reduce(reduce, []);
+    // @ts-ignore
+    selector2 = selector2.reduce(reduce, []);
+    return selector1 == null || selector2 == null ? null : {
+        eq: eq(selector1, selector2),
+        match,
+        selector1,
+        selector2
+    };
+}
 function reduceSelector(selector) {
     if (selector.length == 0) {
         return null;
@@ -2787,49 +2974,75 @@ function reduceSelector(selector) {
         }
         optimized.push(item);
     }
+    while (optimized.length > 0) {
+        const last = optimized.at(-1);
+        if ((last == ' ' || combinators.includes(last))) {
+            optimized.pop();
+            continue;
+        }
+        break;
+    }
     selector.forEach((selector) => selector.splice(0, optimized.length));
     // combinator
     if (combinators.includes(optimized.at(-1))) {
         const combinator = optimized.pop();
         selector.forEach(selector => selector.unshift(combinator));
     }
-    if (optimized.at(-1) == ' ') {
-        optimized.pop();
-    }
     let reducible = optimized.length == 1;
+    if (optimized[0] == '&' && optimized[1] == ' ') {
+        optimized.splice(0, 2);
+    }
     if (optimized.length == 0 ||
-        optimized[0].charAt(0) == '&' ||
-        selector.length == 1) {
+        (optimized[0].charAt(0) == '&' ||
+            selector.length == 1)) {
         return {
             match: false,
             optimized,
-            selector,
-            reducible: selector.length > 1 && selector.every((selector) => !['>', '+', '~'].includes(selector[0]))
+            selector: selector.map(selector => selector[0] == '&' && selector[1] == ' ' ? selector.slice(2) : selector),
+            reducible: selector.length > 1 && selector.every((selector) => !combinators.includes(selector[0]))
         };
     }
     return {
         match: true,
         optimized,
         selector: selector.reduce((acc, curr) => {
+            let hasCompound = true;
+            if (hasCompound && curr.length > 0) {
+                hasCompound = !['&'].concat(combinators).includes(curr[0].charAt(0));
+            }
             // @ts-ignore
-            if (curr.length > 0 && curr[0] == ' ') {
-                curr.shift();
+            if (hasCompound && curr[0] == ' ') {
+                hasCompound = false;
+                curr.unshift('&');
             }
             if (curr.length == 0) {
                 curr.push('&');
+                hasCompound = false;
             }
             if (reducible) {
                 const chr = curr[0].charAt(0);
                 // @ts-ignore
                 reducible = chr == '.' || chr == ':' || isIdentStart(chr.codePointAt(0));
             }
-            acc.push(curr);
+            acc.push(hasCompound ? ['&'].concat(curr) : curr);
             return acc;
         }, []),
         reducible: selector.every((selector) => !['>', '+', '~', '&'].includes(selector[0]))
     };
 }
-function reducer(acc, curr) {
+function reducer(acc, curr, index, array) {
+    // trim :is()
+    if (array.length == 1 && array[0][0] == ':is(' && array[0].at(-1) == ')') {
+        curr = curr.slice(1, -1);
+    }
+    if (curr[0] == '&') {
+        if (curr[1] == ' ') {
+            curr.splice(0, 2);
+        }
+        else if (combinators.includes(curr[1])) {
+            curr.splice(0, 1);
+        }
+    }
     acc.push(curr.join(''));
     return acc;
 }
@@ -3571,13 +3784,13 @@ async function parse$1(iterator, opt = {}) {
                 buffer = value;
                 break;
             case '>':
-                if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
-                    tokens.pop();
-                }
                 if (buffer !== '') {
                     pushToken(getType(buffer));
                     buffer = '';
                 }
+                if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
+                    tokens.pop();
+                }
                 pushToken({ typ: 'Gt' });
                 consumeWhiteSpace();
                 break;
@@ -4016,7 +4229,7 @@ function* doWalk(node, parent, root) {
     yield { node, parent, root };
     if ('chi' in node) {
         for (const child of node.chi) {
-            yield* doWalk(child, node, (root == null ? node : root));
+            yield* doWalk(child, node, (root ?? node));
         }
     }
 }
diff --git a/dist/lib/parser/deduplicate.js b/dist/lib/parser/deduplicate.js
index 0449579..6e3ad93 100644
--- a/dist/lib/parser/deduplicate.js
+++ b/dist/lib/parser/deduplicate.js
@@ -1,4 +1,4 @@
-import { isIdentStart } from './utils/syntax.js';
+import { isIdentStart, isWhiteSpace } from './utils/syntax.js';
 import { getConfig } from './utils/config.js';
 import { PropertyList } from './declaration/list.js';
 import { eq } from './utils/eq.js';
@@ -6,6 +6,53 @@ import { render } from '../renderer/render.js';
 
 const configuration = getConfig();
 const combinators = ['+', '>', '~'];
+const notEndingWith = ['(', '['].concat(combinators);
+function wrapNodes(previous, node, match, ast, i, nodeIndex) {
+    // @ts-ignore
+    let pSel = match.selector1.reduce(reducer, []).join(',');
+    // @ts-ignore
+    let nSel = match.selector2.reduce(reducer, []).join(',');
+    // @ts-ignore
+    const wrapper = { ...previous, chi: [], sel: match.match.reduce(reducer, []).join(',') };
+    // @ts-ignore
+    Object.defineProperty(wrapper, 'raw', {
+        enumerable: false,
+        writable: true,
+        // @ts-ignore
+        value: match.match.map(t => t.slice())
+    });
+    if (pSel == '&' || pSel === '') {
+        // @ts-ignore
+        wrapper.chi.push(...previous.chi);
+        // @ts-ignore
+        if ((nSel == '&' || nSel === '') && hasOnlyDeclarations(previous)) {
+            // @ts-ignore
+            wrapper.chi.push(...node.chi);
+        }
+        else {
+            // @ts-ignore
+            wrapper.chi.push(node);
+        }
+    }
+    else {
+        // @ts-ignore
+        wrapper.chi.push(previous, node);
+    }
+    // @ts-ignore
+    ast.chi.splice(i, 1, wrapper);
+    // @ts-ignore
+    ast.chi.splice(nodeIndex, 1);
+    // @ts-ignore
+    previous.sel = pSel;
+    // @ts-ignore
+    previous.raw = match.selector1;
+    // @ts-ignore
+    node.sel = nSel;
+    // @ts-ignore
+    node.raw = match.selector2;
+    reduceRuleSelector(wrapper);
+    return wrapper;
+}
 function deduplicate(ast, options = {}, recursive = false) {
     // @ts-ignore
     if (('chi' in ast) && ast.chi?.length > 0) {
@@ -42,62 +89,21 @@ function deduplicate(ast, options = {}, recursive = false) {
             if (node.typ == 'Rule') {
                 reduceRuleSelector(node);
                 let wrapper;
+                let match;
                 // @ts-ignore
                 if (options.nestingRules) {
-                    // if (node.sel == '.card>hr') {
-                    //
-                    //     console.error({idem: previous == node, previous, node});
-                    // }
                     // @ts-ignore
-                    if (previous != null) {
+                    if (previous != null && previous.typ == 'Rule') {
+                        reduceRuleSelector(previous);
                         // @ts-ignore
-                        if (node.optimized != null &&
-                            // @ts-ignore
-                            previous.optimized != null &&
-                            // @ts-ignore
-                            node.optimized.optimized.length > 0 &&
-                            // @ts-ignore
-                            previous.optimized.optimized.length > 0 &&
+                        match = matchSelectors(previous.raw, node.raw, ast.typ);
+                        // @ts-ignore
+                        if (match != null) {
                             // @ts-ignore
-                            node.optimized.optimized[0] == previous.optimized.optimized[0]) {
+                            wrapper = wrapNodes(previous, node, match, ast, i, nodeIndex);
+                            nodeIndex = i - 1;
                             // @ts-ignore
-                            if (hasOnlyDeclarations(previous)) {
-                                // @ts-ignore
-                                let pSel = reduceRawTokens(previous.optimized.selector);
-                                if (pSel === '') {
-                                    // @ts-ignore
-                                    pSel = previous.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                let nSel = reduceRawTokens(node.optimized.selector);
-                                if (nSel === '') {
-                                    // @ts-ignore
-                                    nSel = node.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                wrapper = { ...node, chi: [], sel: node.optimized.optimized[0] };
-                                // @ts-ignore
-                                Object.defineProperty(wrapper, 'raw', {
-                                    enumerable: false,
-                                    writable: true,
-                                    // @ts-ignore
-                                    value: [[node.optimized.optimized[0].slice()]]
-                                });
-                                // @ts-ignore
-                                previous.sel = pSel === '' ? '&' : pSel; // reduceRawTokens(previous.optimized.selector);
-                                // @ts-ignore
-                                previous.raw = pSel === '' ? [['&']] : previous.optimized.selector.slice();
-                                // @ts-ignore
-                                node.sel = nSel === '' ? '&' : nSel; // reduceRawTokens(node.optimized.selector);
-                                // @ts-ignore
-                                node.raw = nSel === '' ? [['&']] : node.optimized.selector.slice();
-                                // @ts-ignore
-                                wrapper.chi.push(previous, node);
-                                // @ts-ignore
-                                ast.chi.splice(i, 1, wrapper);
-                                // @ts-ignore
-                                ast.chi.splice(nodeIndex, 1);
-                            }
+                            previous = ast.chi[nodeIndex];
                         }
                     }
                     // @ts-ignore
@@ -107,49 +113,26 @@ function deduplicate(ast, options = {}, recursive = false) {
                             // @ts-ignore
                             const nextNode = ast.chi[i];
                             // @ts-ignore
-                            if (nextNode.typ != 'Rule' || nextNode.raw == null) {
+                            if (nextNode.typ != 'Rule') {
+                                // i--;
+                                // previous = wrapper;
+                                // nodeIndex = i;
                                 break;
                             }
                             reduceRuleSelector(nextNode);
                             // @ts-ignore
-                            if (nextNode.raw.length != 1 || !eq(wrapper.raw[0], nextNode.raw[0].slice(0, wrapper.raw[0].length))) {
-                                break;
-                            }
-                            // @ts-ignore
-                            nextNode.raw[0].splice(0, wrapper.raw[0].length);
+                            match = matchSelectors(wrapper.raw, nextNode.raw, ast.typ);
                             // @ts-ignore
-                            trimRawToken(nextNode.raw[0]);
-                            // @ts-ignore
-                            if (nextNode.raw[0].length == 0 ||
-                                // @ts-ignore
-                                (nextNode.raw.length == 1 && nextNode.raw[0] == '&')) {
-                                if (hasOnlyDeclarations(wrapper)) {
-                                    // @ts-ignore
-                                    wrapper.chi.push(...nextNode.chi);
-                                    // @ts-ignore
-                                    ast.chi.splice(i, 1);
-                                    continue;
-                                }
-                                else {
-                                    // @ts-ignore
-                                    nextNode.raw[0].push('&');
-                                }
+                            if (match == null) {
+                                break;
                             }
                             // @ts-ignore
-                            nextNode.sel = nextNode.raw.reduce((acc, curr) => {
-                                acc.push(curr.join(''));
-                                return acc;
-                            }, []).join(',');
-                            // @ts-ignore
-                            wrapper.chi.push(nextNode);
-                            // @ts-ignore
-                            ast.chi.splice(i, 1);
-                            node = wrapper;
+                            wrapper = wrapNodes(wrapper, nextNode, match, ast, i, nodeIndex);
                         }
-                        deduplicate(wrapper, options, recursive);
-                        nodeIndex = i;
+                        nodeIndex = --i;
                         // @ts-ignore
-                        previous = ast.chi[i];
+                        previous = ast.chi[nodeIndex];
+                        deduplicate(wrapper, options, recursive);
                         continue;
                     }
                     // @ts-ignore
@@ -168,7 +151,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                             value: [[node.optimized.optimized[0]]]
                         });
                         // @ts-ignore
-                        node.sel = reduceRawTokens(node.optimized.selector);
+                        node.sel = node.optimized.selector.reduce(reducer, []).join(',');
                         // @ts-ignore
                         node.raw = node.optimized.selector.slice();
                         // @ts-ignore
@@ -178,6 +161,34 @@ function deduplicate(ast, options = {}, recursive = false) {
                         node = wrapper;
                     }
                 }
+                // @ts-ignore
+                else if (node.optimized?.match) {
+                    let wrap = true;
+                    // @ts-ignore
+                    const selector = node.optimized.selector.reduce((acc, curr) => {
+                        if (curr[0] == '&') {
+                            if (curr[1] == ' ') {
+                                curr.splice(0, 2);
+                            }
+                            else {
+                                if (ast.typ != 'Rule' && combinators.includes(curr[1])) {
+                                    wrap = false;
+                                }
+                                else {
+                                    curr.splice(0, 1);
+                                }
+                            }
+                        }
+                        else if (combinators.includes(curr[0])) {
+                            curr.unshift('&');
+                        }
+                        // @ts-ignore
+                        acc.push(curr.map(t => t.replaceAll('&', node.optimized.optimized[0])).join(''));
+                        return acc;
+                    }, []);
+                    // @ts-ignore
+                    node.sel = (wrap ? node.optimized.optimized[0] : '') + `:is(${selector.join(',')})`;
+                }
             }
             // @ts-ignore
             if (previous != null && 'chi' in previous && ('chi' in node)) {
@@ -206,6 +217,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                             ast.chi.splice(nodeIndex, 1);
                             // @ts-ignore
                             if (hasDeclaration(node)) {
+                                // @ts-ignore
                                 deduplicateRule(node);
                             }
                             else {
@@ -250,6 +262,7 @@ function deduplicate(ast, options = {}, recursive = false) {
                 if (recursive && previous != node) {
                     // @ts-ignore
                     if (hasDeclaration(previous)) {
+                        // @ts-ignore
                         deduplicateRule(previous);
                     }
                     else {
@@ -347,31 +360,40 @@ function deduplicateRule(ast) {
     ast.chi = children.concat(ast.chi?.slice(k));
     return ast;
 }
-function reduceRawTokens(raw) {
-    return raw.reduce((acc, curr) => {
-        acc.push(curr.join(''));
-        return acc;
-    }, []).join(',');
-}
-function trimRawToken(raw) {
-    while (raw.length > 0) {
-        if (raw[0] == ' ') {
-            raw.shift();
-            continue;
-        }
-        break;
-    }
-}
 function splitRule(buffer) {
-    const result = [];
+    const result = [[]];
     let str = '';
     for (let i = 0; i < buffer.length; i++) {
         let chr = buffer.charAt(i);
+        if (isWhiteSpace(chr.charCodeAt(0))) {
+            let k = i;
+            while (k + 1 < buffer.length) {
+                if (isWhiteSpace(buffer[k + 1].charCodeAt(0))) {
+                    k++;
+                    continue;
+                }
+                break;
+            }
+            if (str !== '') {
+                // @ts-ignore
+                result.at(-1).push(str);
+                str = '';
+            }
+            // @ts-ignore
+            if (result.at(-1).length > 0) {
+                // @ts-ignore
+                result.at(-1).push(' ');
+            }
+            i = k;
+            continue;
+        }
         if (chr == ',') {
             if (str !== '') {
-                result.push(str);
+                // @ts-ignore
+                result.at(-1).push(str);
                 str = '';
             }
+            result.push([]);
             continue;
         }
         str += chr;
@@ -421,41 +443,45 @@ function splitRule(buffer) {
         }
     }
     if (str !== '') {
-        result.push(str);
+        // @ts-ignore
+        result.at(-1).push(str);
     }
     return result;
 }
 function reduceRuleSelector(node) {
+    if (node.raw == null) {
+        Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: splitRule(node.sel) });
+    }
     // @ts-ignore
-    if (node.raw != null) {
-        // @ts-ignore
-        let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
-            acc.push(curr.slice());
-            return acc;
-        }, []));
-        if (optimized != null) {
-            Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
-        }
-        if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
-            const raw = [
-                [
-                    optimized.optimized[0], ':is('
-                ].concat(optimized.selector.reduce((acc, curr) => {
-                    if (acc.length > 0) {
-                        acc.push(',');
-                    }
-                    acc.push(...curr);
-                    return acc;
-                }, [])).concat(')')
-            ];
-            const sel = raw[0].join('');
-            if (sel.length < node.sel.length) {
-                node.sel = sel;
-                // node.raw = raw;
-                Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
-            }
+    // if (node.raw != null) {
+    // @ts-ignore
+    let optimized = reduceSelector(node.raw.reduce((acc, curr) => {
+        acc.push(curr.slice());
+        return acc;
+    }, []));
+    if (optimized != null) {
+        Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
+    }
+    if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
+        const raw = [
+            [
+                optimized.optimized[0], ':is('
+            ].concat(optimized.selector.reduce((acc, curr) => {
+                if (acc.length > 0) {
+                    acc.push(',');
+                }
+                acc.push(...curr);
+                return acc;
+            }, [])).concat(')')
+        ];
+        const sel = raw[0].join('');
+        if (sel.length < node.sel.length) {
+            node.sel = sel;
+            // node.raw = raw;
+            Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
         }
     }
+    // }
 }
 function diff(n1, n2, options = {}) {
     let node1 = n1;
@@ -476,25 +502,25 @@ function diff(n1, n2, options = {}) {
     // @ts-ignore
     const raw1 = node1.raw;
     // @ts-ignore
-    const optimized1 = node1.optimized;
+    // const optimized1 = node1.optimized;
     // @ts-ignore
     const raw2 = node2.raw;
     // @ts-ignore
-    const optimized2 = node2.optimized;
+    // const optimized2 = node2.optimized;
     node1 = { ...node1, chi: node1.chi.slice() };
     node2 = { ...node2, chi: node2.chi.slice() };
     if (raw1 != null) {
         Object.defineProperty(node1, 'raw', { enumerable: false, writable: true, value: raw1 });
     }
-    if (optimized1 != null) {
-        Object.defineProperty(node1, 'optimized', { enumerable: false, writable: true, value: optimized1 });
-    }
+    // if (optimized1 != null) {
+    //     Object.defineProperty(node1, 'optimized', {enumerable: false, writable: true, value: optimized1});
+    // }
     if (raw2 != null) {
         Object.defineProperty(node2, 'raw', { enumerable: false, writable: true, value: raw2 });
     }
-    if (optimized2 != null) {
-        Object.defineProperty(node2, 'optimized', { enumerable: false, writable: true, value: optimized2 });
-    }
+    // if (optimized2 != null) {
+    //     Object.defineProperty(node2, 'optimized', {enumerable: false, writable: true, value: optimized2});
+    // }
     const intersect = [];
     while (i--) {
         if (node1.chi[i].typ == 'Comment') {
@@ -522,7 +548,7 @@ function diff(n1, n2, options = {}) {
     const result = (intersect.length == 0 ? null : {
         ...node1,
         // @ts-ignore
-        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(),
+        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(','),
         chi: intersect.reverse()
     });
     if (result == null || [n1, n2].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0) <= [node1, node2, result].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0)) {
@@ -531,6 +557,167 @@ function diff(n1, n2, options = {}) {
     }
     return { result, node1: exchanged ? node2 : node1, node2: exchanged ? node2 : node2 };
 }
+function matchSelectors(selector1, selector2, parentType) {
+    let match = [[]];
+    const j = Math.min(selector1.reduce((acc, curr) => Math.min(acc, curr.length), selector1.length > 0 ? selector1[0].length : 0), selector2.reduce((acc, curr) => Math.min(acc, curr.length), selector2.length > 0 ? selector2[0].length : 0));
+    let i = 0;
+    let k;
+    let l;
+    let token;
+    let matching = true;
+    let matchFunction = 0;
+    let inAttr = 0;
+    for (; i < j; i++) {
+        k = 0;
+        token = selector1[0][i];
+        for (; k < selector1.length; k++) {
+            if (selector1[k][i] != token) {
+                matching = false;
+                break;
+            }
+        }
+        if (matching) {
+            l = 0;
+            for (; l < selector2.length; l++) {
+                if (selector2[l][i] != token) {
+                    matching = false;
+                    break;
+                }
+            }
+        }
+        if (!matching) {
+            break;
+        }
+        if (token == ',') {
+            match.push([]);
+        }
+        else {
+            if (token.endsWith('(')) {
+                matchFunction++;
+            }
+            if (token.endsWith('[')) {
+                inAttr++;
+            }
+            else if (token == ')') {
+                matchFunction--;
+            }
+            else if (token == ']') {
+                inAttr--;
+            }
+            match.at(-1).push(token);
+        }
+    }
+    // invalid function
+    if (matchFunction != 0 || inAttr != 0) {
+        return null;
+    }
+    if (parentType != 'Rule') {
+        for (const part of match) {
+            if (part.length > 0 && combinators.includes(part[0].charAt(0))) {
+                return null;
+            }
+        }
+    }
+    if (match.length > 1) {
+        console.error(`unsupported multilevel matching`);
+        console.error({ match, selector1, selector2 });
+        return null;
+    }
+    for (const part of match) {
+        while (part.length > 0) {
+            const token = part.at(-1);
+            if (token == ' ' || combinators.includes(token) || notEndingWith.includes(token.at(-1))) {
+                part.pop();
+                continue;
+            }
+            break;
+        }
+    }
+    if (match.every(t => t.length == 0)) {
+        return null;
+    }
+    if (eq([['&']], match)) {
+        return null;
+    }
+    function reduce(acc, curr) {
+        if (acc === null) {
+            return null;
+        }
+        let hasCompoundSelector = true;
+        curr = curr.slice(match[0].length);
+        while (curr.length > 0) {
+            if (curr[0] == ' ') {
+                hasCompoundSelector = false;
+                curr.unshift('&');
+                continue;
+            }
+            break;
+        }
+        // invalid function match
+        if (curr.length > 0 && curr[0].endsWith('(') && curr.at(-1) != ')') {
+            return null;
+        }
+        if (curr.length == 1 && combinators.includes(curr[0].charAt(0))) {
+            return null;
+        }
+        if (hasCompoundSelector && curr.length > 0) {
+            hasCompoundSelector = !['&'].concat(combinators).includes(curr[0].charAt(0));
+        }
+        if (curr[0] == ':is(') {
+            let inFunction = 0;
+            let canReduce = true;
+            const isCompound = curr.reduce((acc, token, index) => {
+                if (index == 0) {
+                    inFunction++;
+                    canReduce = curr[1] == '&';
+                }
+                else if (token.endsWith('(')) {
+                    if (inFunction == 0) {
+                        canReduce = false;
+                    }
+                    inFunction++;
+                }
+                else if (token == ')') {
+                    inFunction--;
+                }
+                else if (token == ',') {
+                    if (!canReduce) {
+                        canReduce = curr[index + 1] == '&';
+                    }
+                    acc.push([]);
+                }
+                else
+                    acc.at(-1)?.push(token);
+                return acc;
+            }, [[]]);
+            if (inFunction > 0) {
+                canReduce = false;
+            }
+            if (canReduce) {
+                curr = isCompound.reduce((acc, curr) => {
+                    if (acc.length > 0) {
+                        acc.push(',');
+                    }
+                    acc.push(...curr);
+                    return acc;
+                }, []);
+            }
+        }
+        // @todo: check hasCompoundSelector && curr[0] == '&' && curr[1] == ' '
+        acc.push(match.length == 0 ? ['&'] : (hasCompoundSelector && curr[0] != '&' && (curr.length == 0 || !combinators.includes(curr[0].charAt(0))) ? ['&'].concat(curr) : curr));
+        return acc;
+    }
+    // @ts-ignore
+    selector1 = selector1.reduce(reduce, []);
+    // @ts-ignore
+    selector2 = selector2.reduce(reduce, []);
+    return selector1 == null || selector2 == null ? null : {
+        eq: eq(selector1, selector2),
+        match,
+        selector1,
+        selector2
+    };
+}
 function reduceSelector(selector) {
     if (selector.length == 0) {
         return null;
@@ -554,49 +741,75 @@ function reduceSelector(selector) {
         }
         optimized.push(item);
     }
+    while (optimized.length > 0) {
+        const last = optimized.at(-1);
+        if ((last == ' ' || combinators.includes(last))) {
+            optimized.pop();
+            continue;
+        }
+        break;
+    }
     selector.forEach((selector) => selector.splice(0, optimized.length));
     // combinator
     if (combinators.includes(optimized.at(-1))) {
         const combinator = optimized.pop();
         selector.forEach(selector => selector.unshift(combinator));
     }
-    if (optimized.at(-1) == ' ') {
-        optimized.pop();
-    }
     let reducible = optimized.length == 1;
+    if (optimized[0] == '&' && optimized[1] == ' ') {
+        optimized.splice(0, 2);
+    }
     if (optimized.length == 0 ||
-        optimized[0].charAt(0) == '&' ||
-        selector.length == 1) {
+        (optimized[0].charAt(0) == '&' ||
+            selector.length == 1)) {
         return {
             match: false,
             optimized,
-            selector,
-            reducible: selector.length > 1 && selector.every((selector) => !['>', '+', '~'].includes(selector[0]))
+            selector: selector.map(selector => selector[0] == '&' && selector[1] == ' ' ? selector.slice(2) : selector),
+            reducible: selector.length > 1 && selector.every((selector) => !combinators.includes(selector[0]))
         };
     }
     return {
         match: true,
         optimized,
         selector: selector.reduce((acc, curr) => {
+            let hasCompound = true;
+            if (hasCompound && curr.length > 0) {
+                hasCompound = !['&'].concat(combinators).includes(curr[0].charAt(0));
+            }
             // @ts-ignore
-            if (curr.length > 0 && curr[0] == ' ') {
-                curr.shift();
+            if (hasCompound && curr[0] == ' ') {
+                hasCompound = false;
+                curr.unshift('&');
             }
             if (curr.length == 0) {
                 curr.push('&');
+                hasCompound = false;
             }
             if (reducible) {
                 const chr = curr[0].charAt(0);
                 // @ts-ignore
                 reducible = chr == '.' || chr == ':' || isIdentStart(chr.codePointAt(0));
             }
-            acc.push(curr);
+            acc.push(hasCompound ? ['&'].concat(curr) : curr);
             return acc;
         }, []),
         reducible: selector.every((selector) => !['>', '+', '~', '&'].includes(selector[0]))
     };
 }
-function reducer(acc, curr) {
+function reducer(acc, curr, index, array) {
+    // trim :is()
+    if (array.length == 1 && array[0][0] == ':is(' && array[0].at(-1) == ')') {
+        curr = curr.slice(1, -1);
+    }
+    if (curr[0] == '&') {
+        if (curr[1] == ' ') {
+            curr.splice(0, 2);
+        }
+        else if (combinators.includes(curr[1])) {
+            curr.splice(0, 1);
+        }
+    }
     acc.push(curr.join(''));
     return acc;
 }
diff --git a/dist/lib/parser/parse.js b/dist/lib/parser/parse.js
index e5c1777..3a4f960 100644
--- a/dist/lib/parser/parse.js
+++ b/dist/lib/parser/parse.js
@@ -740,13 +740,13 @@ async function parse(iterator, opt = {}) {
                 buffer = value;
                 break;
             case '>':
-                if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
-                    tokens.pop();
-                }
                 if (buffer !== '') {
                     pushToken(getType(buffer));
                     buffer = '';
                 }
+                if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
+                    tokens.pop();
+                }
                 pushToken({ typ: 'Gt' });
                 consumeWhiteSpace();
                 break;
diff --git a/dist/lib/walker/walk.js b/dist/lib/walker/walk.js
index 847f5a1..eb8c216 100644
--- a/dist/lib/walker/walk.js
+++ b/dist/lib/walker/walk.js
@@ -6,7 +6,7 @@ function* doWalk(node, parent, root) {
     yield { node, parent, root };
     if ('chi' in node) {
         for (const child of node.chi) {
-            yield* doWalk(child, node, (root == null ? node : root));
+            yield* doWalk(child, node, (root ?? node));
         }
     }
 }
diff --git a/package.json b/package.json
index b27e4d7..fea45d9 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@tbela99/css-parser",
   "description": "CSS parser for node and the browser",
-  "version": "0.0.1-alpha4",
+  "version": "0.0.1-alpha5",
   "exports": {
     ".": "./dist/index.js",
     "./web": "./dist/web/index.js",
@@ -45,7 +45,6 @@
     "@web/test-runner": "^0.16.1",
     "@webref/css": "^6.5.9",
     "c8": "^8.0.1",
-    "glob": "^10.3.0",
     "mocha": "^10.2.0",
     "rollup": "^3.20.1",
     "rollup-plugin-dts": "^5.3.0",
diff --git a/rollup.config.mjs b/rollup.config.mjs
index fc857c2..6354e57 100644
--- a/rollup.config.mjs
+++ b/rollup.config.mjs
@@ -1,27 +1,14 @@
 import dts from 'rollup-plugin-dts';
 import typescript from "@rollup/plugin-typescript";
 import nodeResolve from "@rollup/plugin-node-resolve";
-import {glob} from "glob";
 import terser from "@rollup/plugin-terser";
 import json from "@rollup/plugin-json";
 import commonjs from "@rollup/plugin-commonjs";
 
-export default [...await glob(['./test/specs/**/*.spec.ts', './test/specs/**/*.web-spec.ts']).then(files => files.map(input => {
-    return {
-        input,
-        plugins: [nodeResolve(), commonjs({transformMixedEsModules:true}), json(), typescript()],
-        output:
-            {
-                banner: `/* generate from ${input} */`,
-                file: `${input.replace(/\.spec\.ts$/, '.test.js').replace(/\.web-spec\.ts$/, '.web.js').replace('/specs/', '/spec-runners/')}`,
-                format: 'es'
-            }
-    }
-}))
-].concat([
+export default [
     {
         input: 'src/index.ts',
-        plugins: [nodeResolve(), commonjs({transformMixedEsModules:true}), json(), typescript()],
+        plugins: [nodeResolve(), commonjs({transformMixedEsModules: true}), json(), typescript()],
         output: [
             {
                 // file: './dist/index.mjs',
@@ -38,7 +25,7 @@ export default [...await glob(['./test/specs/**/*.spec.ts', './test/specs/**/*.w
     },
     {
         input: 'src/web/index.ts',
-        plugins: [nodeResolve(), commonjs({transformMixedEsModules:true}), json(), typescript()],
+        plugins: [nodeResolve(), commonjs({transformMixedEsModules: true}), json(), typescript()],
         output: [
             {
                 // file: './dist/index.mjs',
@@ -62,4 +49,4 @@ export default [...await glob(['./test/specs/**/*.spec.ts', './test/specs/**/*.w
             format: 'es'
         }
     }
-])
\ No newline at end of file
+];
\ No newline at end of file
diff --git a/src/@types/index.d.ts b/src/@types/index.d.ts
index dbd3c10..0a0c0ea 100644
--- a/src/@types/index.d.ts
+++ b/src/@types/index.d.ts
@@ -79,6 +79,14 @@ export interface ParseTokenOptions extends ParserOptions {
     parseColor?: boolean;
 }
 
+
+export interface MatchedSelector {
+    match: string[][];
+    selector1: string[][];
+    selector2: string[][];
+    eq: boolean
+}
+
 export interface Position {
 
     ind: number;
diff --git a/src/lib/parser/deduplicate.ts b/src/lib/parser/deduplicate.ts
index ad5edc3..12aca7c 100644
--- a/src/lib/parser/deduplicate.ts
+++ b/src/lib/parser/deduplicate.ts
@@ -1,5 +1,14 @@
-import {getConfig, isIdentStart} from "./utils";
-import {AstAtRule, AstDeclaration, AstNode, AstRule, OptimizedSelector, ParserOptions} from "../../@types";
+import {getConfig, isIdentStart, isWhiteSpace} from "./utils";
+import {
+    AstAtRule,
+    AstDeclaration,
+    AstNode,
+    AstRule, AstRuleStyleSheet,
+    MatchedSelector,
+    NodeType,
+    OptimizedSelector,
+    ParserOptions
+} from "../../@types";
 import {PropertyList} from "./declaration";
 import {eq} from "./utils/eq";
 import {render} from "../renderer";
@@ -7,14 +16,73 @@ import {render} from "../renderer";
 
 const configuration = getConfig();
 const combinators = ['+', '>', '~'];
+const notEndingWith = ['(', '['].concat(combinators);
+
+function wrapNodes(previous: AstRule, node: AstRule, match: MatchedSelector, ast: AstNode, i: number, nodeIndex: number): AstRule {
+
+    // @ts-ignore
+    let pSel = match.selector1.reduce(reducer, []).join(',');
+
+    // @ts-ignore
+    let nSel = match.selector2.reduce(reducer, []).join(',');
+
+// @ts-ignore
+    const wrapper = <AstRule>{...previous, chi: [], sel: match.match.reduce(reducer, []).join(',')};
+
+    // @ts-ignore
+    Object.defineProperty(wrapper, 'raw', {
+        enumerable: false,
+        writable: true,
+        // @ts-ignore
+        value: match.match.map(t => t.slice())
+    });
+
+    if (pSel == '&' || pSel === '') {
+
+        // @ts-ignore
+        wrapper.chi.push(...previous.chi);
+
+        // @ts-ignore
+        if ((nSel == '&' || nSel === '') && hasOnlyDeclarations(previous)) {
+
+            // @ts-ignore
+            wrapper.chi.push(...node.chi);
+        } else {
+
+            // @ts-ignore
+            wrapper.chi.push(node);
+        }
+    } else {
+
+        // @ts-ignore
+        wrapper.chi.push(previous, node);
+    }
+
+    // @ts-ignore
+    ast.chi.splice(i, 1, wrapper);
+    // @ts-ignore
+    ast.chi.splice(nodeIndex, 1);
+    // @ts-ignore
+    previous.sel = pSel;
+    // @ts-ignore
+    previous.raw = match.selector1;
+    // @ts-ignore
+    node.sel = nSel;
+    // @ts-ignore
+    node.raw = match.selector2;
+
+
+    reduceRuleSelector(wrapper);
+    return wrapper;
+}
 
 export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive: boolean = false): AstNode {
     // @ts-ignore
     if (('chi' in ast) && ast.chi?.length > 0) {
-        let i = 0;
-        let previous;
-        let node;
-        let nodeIndex;
+        let i: number = 0;
+        let previous: AstNode;
+        let node: AstNode;
+        let nodeIndex: number;
         // @ts-ignore
         for (; i < ast.chi.length; i++) {
             // @ts-ignore
@@ -23,6 +91,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
             }
             // @ts-ignore
             node = ast.chi[i];
+
             // @ts-ignore
             if (previous == node) {
                 // console.error('idem!');
@@ -31,6 +100,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                 i--;
                 continue;
             }
+
             if (node.typ == 'AtRule' && (<AstAtRule>node).nam == 'font-face') {
                 continue;
             }
@@ -42,117 +112,69 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
             }
             // @ts-ignore
             if (node.typ == 'Rule') {
+
                 reduceRuleSelector(<AstRule>node);
-                let wrapper;
+                let wrapper: AstRule;
+                let match;
+
                 // @ts-ignore
                 if (options.nestingRules) {
-                    // if (node.sel == '.card>hr') {
-                    //
-                    //     console.error({idem: previous == node, previous, node});
-                    // }
+
                     // @ts-ignore
-                    if (previous != null) {
+                    if (previous != null && previous.typ == 'Rule') {
+
+                        reduceRuleSelector(<AstRule>previous);
+
                         // @ts-ignore
-                        if (node.optimized != null &&
-                            // @ts-ignore
-                            previous.optimized != null &&
-                            // @ts-ignore
-                            node.optimized.optimized.length > 0 &&
-                            // @ts-ignore
-                            previous.optimized.optimized.length > 0 &&
+                        match = matchSelectors(previous.raw, node.raw, ast.typ);
+
+                        // @ts-ignore
+                        if (match != null) {
+
                             // @ts-ignore
-                            node.optimized.optimized[0] == previous.optimized.optimized[0]) {
+                            wrapper = wrapNodes(previous, node, match, ast, i, nodeIndex);
+                            nodeIndex = i - 1;
                             // @ts-ignore
-                            if (hasOnlyDeclarations(previous)) {
-                                // @ts-ignore
-                                let pSel = reduceRawTokens(previous.optimized.selector);
-                                if (pSel === '') {
-                                    // @ts-ignore
-                                    pSel = previous.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                let nSel = reduceRawTokens(node.optimized.selector);
-                                if (nSel === '') {
-                                    // @ts-ignore
-                                    nSel = node.optimized.optimized.slice(1).join('').trim();
-                                }
-                                // @ts-ignore
-                                wrapper = { ...node, chi: [], sel: node.optimized.optimized[0] };
-                                // @ts-ignore
-                                Object.defineProperty(wrapper, 'raw', {
-                                    enumerable: false,
-                                    writable: true,
-                                    // @ts-ignore
-                                    value: [[node.optimized.optimized[0].slice()]]
-                                });
-                                // @ts-ignore
-                                previous.sel = pSel === '' ? '&' : pSel; // reduceRawTokens(previous.optimized.selector);
-                                // @ts-ignore
-                                previous.raw = pSel === '' ? [['&']] : previous.optimized.selector.slice();
-                                // @ts-ignore
-                                node.sel = nSel === '' ? '&' : nSel; // reduceRawTokens(node.optimized.selector);
-                                // @ts-ignore
-                                node.raw = nSel === '' ? [['&']] : node.optimized.selector.slice();
-                                // @ts-ignore
-                                wrapper.chi.push(previous, node);
-                                // @ts-ignore
-                                ast.chi.splice(i, 1, wrapper);
-                                // @ts-ignore
-                                ast.chi.splice(nodeIndex, 1);
-                            }
+                            previous = ast.chi[nodeIndex];
                         }
                     }
+
                     // @ts-ignore
                     if (wrapper != null) {
                         // @ts-ignore
                         while (i < ast.chi.length) {
+
                             // @ts-ignore
-                            const nextNode = ast.chi[i];
+                            const nextNode = <AstRule>ast.chi[i];
+
                             // @ts-ignore
-                            if (nextNode.typ != 'Rule' || nextNode.raw == null) {
+                            if (nextNode.typ != 'Rule') {
+                                // i--;
+                                // previous = wrapper;
+                                // nodeIndex = i;
+
                                 break;
                             }
+
                             reduceRuleSelector(<AstRule>nextNode);
+
                             // @ts-ignore
-                            if (nextNode.raw.length != 1 || !eq(wrapper.raw[0], nextNode.raw[0].slice(0, wrapper.raw[0].length))) {
-                                break;
-                            }
-                            // @ts-ignore
-                            nextNode.raw[0].splice(0, wrapper.raw[0].length);
-                            // @ts-ignore
-                            trimRawToken(nextNode.raw[0]);
+                            match = matchSelectors(wrapper.raw, nextNode.raw, ast.typ);
+
                             // @ts-ignore
-                            if (nextNode.raw[0].length == 0 ||
-                                // @ts-ignore
-                                (nextNode.raw.length == 1 && nextNode.raw[0] == '&')) {
-                                if (hasOnlyDeclarations(<AstRule>wrapper)) {
-                                    // @ts-ignore
-                                    wrapper.chi.push(...(<AstRule>nextNode).chi);
-                                    // @ts-ignore
-                                    ast.chi.splice(i, 1);
-                                    continue;
-                                }
-                                else {
-                                    // @ts-ignore
-                                    nextNode.raw[0].push('&');
-                                }
+                            if (match == null) {
+
+                                break;
                             }
-                            // @ts-ignore
-                            nextNode.sel = nextNode.raw.reduce((acc, curr) => {
-                                acc.push(curr.join(''));
-                                return acc;
-                            }, []).join(',');
 
                             // @ts-ignore
-                            wrapper.chi.push(<AstRule>nextNode);
-                            // @ts-ignore
-                            ast.chi.splice(i, 1);
-                            node = wrapper;
+                            wrapper = wrapNodes(wrapper, nextNode, match, ast, i, nodeIndex);
                         }
-                        deduplicate(wrapper, options, recursive);
-                        nodeIndex = i;
+
+                        nodeIndex = --i;
                         // @ts-ignore
-                        previous = ast.chi[i];
+                        previous = ast.chi[nodeIndex];
+                        deduplicate(<AstRule>wrapper, options, recursive);
                         continue;
                     }
                     // @ts-ignore
@@ -162,7 +184,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                         // @ts-ignore
                         node.optimized.selector.length > 1) {
                         // @ts-ignore
-                        wrapper = { ...node, chi: [], sel: node.optimized.optimized[0] };
+                        wrapper = {...node, chi: [], sel: node.optimized.optimized[0]};
                         // @ts-ignore
                         Object.defineProperty(wrapper, 'raw', {
                             enumerable: false,
@@ -170,8 +192,9 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                             // @ts-ignore
                             value: [[node.optimized.optimized[0]]]
                         });
+
                         // @ts-ignore
-                        node.sel = reduceRawTokens(node.optimized.selector);
+                        node.sel = node.optimized.selector.reduce(reducer, []).join(',');
                         // @ts-ignore
                         node.raw = node.optimized.selector.slice();
                         // @ts-ignore
@@ -181,6 +204,50 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                         node = wrapper;
                     }
                 }
+
+                // @ts-ignore
+                else if (node.optimized?.match) {
+
+                    let wrap: boolean = true;
+                    // @ts-ignore
+                    const selector: string[] = node.optimized.selector.reduce((acc, curr) => {
+
+                        if (curr[0] == '&') {
+
+                            if (curr[1] == ' ') {
+
+                                curr.splice(0, 2);
+                            }
+
+                            else {
+
+                                if (ast.typ != 'Rule' && combinators.includes(curr[1])) {
+
+                                    wrap = false;
+                                }
+
+                                else {
+
+                                    curr.splice(0, 1);
+                                }
+                            }
+                        }
+
+                        else if (combinators.includes(curr[0])) {
+
+                            curr.unshift('&');
+                        }
+
+                        // @ts-ignore
+                        acc.push(curr.map(t => t.replaceAll('&', node.optimized.optimized[0])).join(''));
+
+                        return acc
+
+                    }, []);
+
+                    // @ts-ignore
+                    node.sel = (wrap ? node.optimized.optimized[0] : '') + `:is(${selector.join(',')})`;
+                }
             }
             // @ts-ignore
             if (previous != null && 'chi' in previous && ('chi' in node)) {
@@ -209,17 +276,16 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                             ast.chi.splice(nodeIndex, 1);
                             // @ts-ignore
                             if (hasDeclaration(node)) {
+                                // @ts-ignore
                                 deduplicateRule(node);
-                            }
-                            else {
+                            } else {
                                 deduplicate(node, options, recursive);
                             }
                             i--;
                             previous = node;
                             nodeIndex = i;
                             continue;
-                        }
-                        else if (node.typ == 'Rule' && previous?.typ == 'Rule') {
+                        } else if (node.typ == 'Rule' && previous?.typ == 'Rule') {
                             const intersect = diff(<AstRule>previous, <AstRule>node, options);
                             if (intersect != null) {
                                 if (intersect.node1.chi.length == 0) {
@@ -227,8 +293,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                                     ast.chi.splice(i--, 1);
                                     // @ts-ignore
                                     node = ast.chi[i];
-                                }
-                                else {
+                                } else {
                                     // @ts-ignore
                                     ast.chi.splice(i, 1, intersect.node1);
                                     node = intersect.node1;
@@ -237,8 +302,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                                     // @ts-ignore
                                     ast.chi.splice(nodeIndex, 1, intersect.result);
                                     previous = intersect.result;
-                                }
-                                else {
+                                } else {
                                     // @ts-ignore
                                     ast.chi.splice(nodeIndex, 1, intersect.result, intersect.node2);
                                     previous = intersect.result;
@@ -253,9 +317,9 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
                 if (recursive && previous != node) {
                     // @ts-ignore
                     if (hasDeclaration(previous)) {
+                        // @ts-ignore
                         deduplicateRule(previous);
-                    }
-                    else {
+                    } else {
                         deduplicate(previous, options, recursive);
                     }
                 }
@@ -268,8 +332,7 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
             // @ts-ignore
             if (node.chi.some(n => n.typ == 'Declaration')) {
                 deduplicateRule(<AstRule | AstAtRule>node);
-            }
-            else {
+            } else {
                 // @ts-ignore
                 if (!(node.typ == 'AtRule' && (<AstAtRule>node).nam != 'font-face')) {
                     deduplicate(node, options, recursive);
@@ -279,29 +342,40 @@ export function deduplicate(ast: AstNode, options: ParserOptions = {}, recursive
     }
     return ast;
 }
+
 function hasOnlyDeclarations(node: AstRule): boolean {
     let k: number = node.chi.length;
 
     while (k--) {
+
         if (node.chi[k].typ == 'Comment') {
+
             continue;
         }
+
         return node.chi[k].typ == 'Declaration';
     }
+
     return true;
 }
+
 export function hasDeclaration(node: AstRule): boolean {
+
     // @ts-ignore
     for (let i = 0; i < node.chi?.length; i++) {
+
         // @ts-ignore
         if (node.chi[i].typ == 'Comment') {
+
             continue;
         }
         // @ts-ignore
         return node.chi[i].typ == 'Declaration';
     }
+
     return true;
 }
+
 export function deduplicateRule(ast: AstRule | AstAtRule): AstRule | AstAtRule {
     // @ts-ignore
     if (!('chi' in ast) || ast.chi?.length <= 1) {
@@ -319,8 +393,7 @@ export function deduplicateRule(ast: AstRule | AstAtRule): AstRule | AstAtRule {
             // @ts-ignore
             map.set(node, node);
             continue;
-        }
-        else if (node.typ != 'Declaration') {
+        } else if (node.typ != 'Declaration') {
             break;
         }
         if ((<AstDeclaration>node).nam in configuration.map ||
@@ -331,18 +404,18 @@ export function deduplicateRule(ast: AstRule | AstAtRule): AstRule | AstAtRule {
                 map.set(shorthand, new PropertyList());
             }
             map.get(shorthand).add(node);
-        }
-        else {
+        } else {
             map.set((<AstDeclaration>node).nam, node);
         }
     }
+
     const children = [];
+
     for (let child of map.values()) {
         if (child instanceof PropertyList) {
             // @ts-ignore
             children.push(...child);
-        }
-        else {
+        } else {
             // @ts-ignore
             children.push(child);
         }
@@ -351,6 +424,7 @@ export function deduplicateRule(ast: AstRule | AstAtRule): AstRule | AstAtRule {
     ast.chi = children.concat(ast.chi?.slice(k));
     return ast;
 }
+
 function reduceRawTokens(raw: string[][]) {
 
     return raw.reduce((acc, curr) => {
@@ -358,6 +432,7 @@ function reduceRawTokens(raw: string[][]) {
         return acc;
     }, []).join(',');
 }
+
 function trimRawToken(raw: string[]) {
     while (raw.length > 0) {
         if (raw[0] == ' ') {
@@ -367,21 +442,57 @@ function trimRawToken(raw: string[]) {
         break;
     }
 }
-function splitRule(buffer: string): string[] {
 
-    const result: string[] = [];
+function splitRule(buffer: string): string[][] {
+
+    const result: string[][] = [[]];
     let str: string = '';
 
     for (let i = 0; i < buffer.length; i++) {
 
         let chr: string = buffer.charAt(i);
 
+        if (isWhiteSpace(chr.charCodeAt(0))) {
+
+            let k = i;
+
+            while (k + 1 < buffer.length) {
+
+                if (isWhiteSpace(buffer[k + 1].charCodeAt(0))) {
+
+                    k++;
+                    continue;
+                }
+
+                break;
+            }
+
+            if (str !== '') {
+
+                // @ts-ignore
+                result.at(-1).push(str);
+                str = '';
+            }
+
+            // @ts-ignore
+            if (result.at(-1).length > 0) {
+
+                // @ts-ignore
+                result.at(-1).push(' ');
+            }
+
+            i = k;
+            continue;
+        }
+
         if (chr == ',') {
             if (str !== '') {
-                result.push(str);
+                // @ts-ignore
+                result.at(-1).push(str);
                 str = '';
             }
 
+            result.push([]);
             continue;
         }
 
@@ -420,8 +531,7 @@ function splitRule(buffer: string): string[] {
                 str += chr;
                 if (chr == open) {
                     inParens++;
-                }
-                else if (chr == close) {
+                } else if (chr == close) {
                     inParens--;
                 }
                 if (inParens == 0) {
@@ -431,44 +541,56 @@ function splitRule(buffer: string): string[] {
             i = k;
         }
     }
+
     if (str !== '') {
-        result.push(str);
+        // @ts-ignore
+        result.at(-1).push(str);
     }
+
     return result;
 }
+
 function reduceRuleSelector(node: AstRule) {
+
+    if (node.raw == null) {
+
+        Object.defineProperty(node, 'raw', {enumerable: false, writable: true, value: splitRule(node.sel)})
+    }
+
     // @ts-ignore
-    if (node.raw != null) {
-        // @ts-ignore
-        let optimized: OptimizedSelector = <OptimizedSelector> reduceSelector(node.raw.reduce((acc, curr) => {
-            acc.push(curr.slice());
-            return acc;
-        }, <string[][]>[]));
+    // if (node.raw != null) {
+    // @ts-ignore
+    let optimized: OptimizedSelector = <OptimizedSelector>reduceSelector(node.raw.reduce((acc, curr) => {
+        acc.push(curr.slice());
+        return acc;
+    }, <string[][]>[]));
 
-        if (optimized != null) {
-            Object.defineProperty(node, 'optimized', { enumerable: false, writable: true, value: optimized });
-        }
-        if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
-            const raw = [
-                [
-                    optimized.optimized[0], ':is('
-                ].concat(optimized.selector.reduce((acc, curr) => {
-                    if (acc.length > 0) {
-                        acc.push(',');
-                    }
-                    acc.push(...curr);
-                    return acc;
-                }, [])).concat(')')
-            ];
-            const sel = raw[0].join('');
-            if (sel.length < node.sel.length) {
-                node.sel = sel;
-                // node.raw = raw;
-                Object.defineProperty(node, 'raw', { enumerable: false, writable: true, value: raw });
-            }
+    if (optimized != null) {
+        Object.defineProperty(node, 'optimized', {enumerable: false, writable: true, value: optimized});
+    }
+    if (optimized != null && optimized.match && optimized.reducible && optimized.selector.length > 1) {
+
+        const raw = [
+            [
+                optimized.optimized[0], ':is('
+            ].concat(optimized.selector.reduce((acc, curr) => {
+                if (acc.length > 0) {
+                    acc.push(',');
+                }
+                acc.push(...curr);
+                return acc;
+            }, [])).concat(')')
+        ];
+        const sel = raw[0].join('');
+        if (sel.length < node.sel.length) {
+            node.sel = sel;
+            // node.raw = raw;
+            Object.defineProperty(node, 'raw', {enumerable: false, writable: true, value: raw});
         }
     }
+    // }
 }
+
 function diff(n1: AstRule, n2: AstRule, options: ParserOptions = {}) {
     let node1 = n1;
     let node2 = n2;
@@ -488,25 +610,25 @@ function diff(n1: AstRule, n2: AstRule, options: ParserOptions = {}) {
     // @ts-ignore
     const raw1 = node1.raw;
     // @ts-ignore
-    const optimized1 = node1.optimized;
+    // const optimized1 = node1.optimized;
     // @ts-ignore
     const raw2 = node2.raw;
     // @ts-ignore
-    const optimized2 = node2.optimized;
-    node1 = { ...node1, chi: node1.chi.slice() };
-    node2 = { ...node2, chi: node2.chi.slice() };
+    // const optimized2 = node2.optimized;
+    node1 = {...node1, chi: node1.chi.slice()};
+    node2 = {...node2, chi: node2.chi.slice()};
     if (raw1 != null) {
-        Object.defineProperty(node1, 'raw', { enumerable: false, writable: true, value: raw1 });
-    }
-    if (optimized1 != null) {
-        Object.defineProperty(node1, 'optimized', { enumerable: false, writable: true, value: optimized1 });
+        Object.defineProperty(node1, 'raw', {enumerable: false, writable: true, value: raw1});
     }
+    // if (optimized1 != null) {
+    //     Object.defineProperty(node1, 'optimized', {enumerable: false, writable: true, value: optimized1});
+    // }
     if (raw2 != null) {
-        Object.defineProperty(node2, 'raw', { enumerable: false, writable: true, value: raw2 });
-    }
-    if (optimized2 != null) {
-        Object.defineProperty(node2, 'optimized', { enumerable: false, writable: true, value: optimized2 });
+        Object.defineProperty(node2, 'raw', {enumerable: false, writable: true, value: raw2});
     }
+    // if (optimized2 != null) {
+    //     Object.defineProperty(node2, 'optimized', {enumerable: false, writable: true, value: optimized2});
+    // }
     const intersect = [];
     while (i--) {
         if (node1.chi[i].typ == 'Comment') {
@@ -534,19 +656,260 @@ function diff(n1: AstRule, n2: AstRule, options: ParserOptions = {}) {
     const result = (intersect.length == 0 ? null : {
         ...node1,
         // @ts-ignore
-        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(),
+        sel: [...new Set([...(n1?.raw?.reduce(reducer, []) || splitRule(n1.sel)).concat(n2?.raw?.reduce(reducer, []) || splitRule(n2.sel))])].join(','),
         chi: intersect.reverse()
     });
     if (result == null || [n1, n2].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0) <= [node1, node2, result].reduce((acc, curr) => curr.chi.length == 0 ? acc : acc + render(curr, options).code.length, 0)) {
         // @ts-ignore
         return null;
     }
-    return { result, node1: exchanged ? node2 : node1, node2: exchanged ? node2 : node2 };
+    return {result, node1: exchanged ? node2 : node1, node2: exchanged ? node2 : node2};
+}
+
+function matchSelectors(selector1: string[][], selector2: string[][], parentType: NodeType): null | MatchedSelector {
+
+    let match: string[][] = [[]];
+    const j = Math.min(
+        selector1.reduce((acc, curr) => Math.min(acc, curr.length), selector1.length > 0 ? selector1[0].length : 0),
+        selector2.reduce((acc, curr) => Math.min(acc, curr.length), selector2.length > 0 ? selector2[0].length : 0)
+    );
+
+    let i: number = 0;
+    let k: number;
+    let l: number;
+    let token: string;
+    let matching: boolean = true;
+    let matchFunction: number = 0;
+    let inAttr: number = 0;
+
+    for (; i < j; i++) {
+
+        k = 0;
+        token = selector1[0][i];
+
+        for (; k < selector1.length; k++) {
+
+            if (selector1[k][i] != token) {
+
+                matching = false;
+                break;
+            }
+        }
+
+        if (matching) {
+
+            l = 0;
+            for (; l < selector2.length; l++) {
+
+                if (selector2[l][i] != token) {
+
+                    matching = false;
+                    break;
+                }
+            }
+        }
+
+        if (!matching) {
+
+            break;
+        }
+
+        if (token == ',') {
+
+            match.push([]);
+        } else {
+
+            if (token.endsWith('(')) {
+
+                matchFunction++;
+            }
+
+            if (token.endsWith('[')) {
+
+                inAttr++;
+            } else if (token == ')') {
+
+                matchFunction--;
+            } else if (token == ']') {
+
+                inAttr--;
+            }
+
+            (<string[]>match.at(-1)).push(token);
+        }
+    }
+
+    // invalid function
+    if (matchFunction != 0 || inAttr != 0) {
+
+        return null;
+    }
+
+    if (parentType != 'Rule') {
+
+        for (const part of match) {
+
+            if (part.length > 0 && combinators.includes(part[0].charAt(0))) {
+
+                return null;
+            }
+        }
+    }
+    if (match.length > 1) {
+
+        console.error(`unsupported multilevel matching`);
+        console.error({match, selector1, selector2});
+        return null;
+    }
+
+    for (const part of match) {
+
+        while (part.length > 0) {
+
+            const token = <string>part.at(-1);
+
+            if (token == ' ' || combinators.includes(token) || notEndingWith.includes(<string>token.at(-1))) {
+
+                part.pop();
+                continue;
+            }
+
+            break;
+        }
+    }
+
+    if (match.every(t => t.length == 0)) {
+
+        return null;
+    }
+
+    if (eq([['&']], match)) {
+
+        return null;
+    }
+
+    function reduce(acc: string[][], curr: string[]) {
+
+        if (acc === null) {
+
+            return null;
+        }
+
+        let hasCompoundSelector = true;
+
+        curr = curr.slice(match[0].length);
+
+        while (curr.length > 0) {
+
+            if (curr[0] == ' ') {
+
+                hasCompoundSelector = false;
+                curr.unshift('&');
+                continue;
+            }
+
+            break;
+        }
+
+        // invalid function match
+        if (curr.length > 0 && curr[0].endsWith('(') && curr.at(-1) != ')') {
+
+            return null;
+        }
+
+        if (curr.length == 1 && combinators.includes(curr[0].charAt(0))) {
+
+            return null;
+        }
+
+        if (hasCompoundSelector && curr.length > 0) {
+
+            hasCompoundSelector = !['&'].concat(combinators).includes(curr[0].charAt(0));
+        }
+
+        if (curr[0] == ':is(') {
+
+            let inFunction = 0;
+            let canReduce = true;
+            const isCompound = curr.reduce((acc, token, index: number) => {
+
+                if (index == 0) {
+
+                    inFunction++;
+                    canReduce = curr[1] == '&';
+                } else if (token.endsWith('(')) {
+
+                    if (inFunction == 0) {
+
+                        canReduce = false;
+                    }
+
+                    inFunction++;
+                } else if (token == ')') {
+
+                    inFunction--;
+                } else if (token == ',') {
+
+                    if (!canReduce) {
+
+                        canReduce = curr[index + 1] == '&';
+                    }
+
+                    acc.push([]);
+                } else acc.at(-1)?.push(token);
+
+                return acc;
+
+            }, <string[][]>[[]]);
+
+            if (inFunction > 0) {
+
+                canReduce = false;
+            }
+
+            if (canReduce) {
+
+                curr = isCompound.reduce((acc, curr) => {
+
+                    if (acc.length > 0) {
+
+                        acc.push(',');
+                    }
+
+                    acc.push(...curr);
+
+                    return acc
+                }, []);
+            }
+        }
+
+        // @todo: check hasCompoundSelector && curr[0] == '&' && curr[1] == ' '
+
+        acc.push(match.length == 0 ? ['&'] : (hasCompoundSelector && curr[0] != '&' && (curr.length == 0 || !combinators.includes(curr[0].charAt(0))) ? ['&'].concat(curr) : curr))
+
+        return acc;
+    }
+
+
+    // @ts-ignore
+    selector1 = selector1.reduce(reduce, <string[][]>[]);
+    // @ts-ignore
+    selector2 = selector2.reduce(reduce, <string[][]>[]);
+
+    return selector1 == null || selector2 == null ? null : {
+        eq: eq(selector1, selector2),
+        match,
+        selector1,
+        selector2
+    }
 }
+
 export function reduceSelector(selector: string[][]) {
+
     if (selector.length == 0) {
         return null;
     }
+
     const optimized: string[] = [];
     const k = selector.reduce((acc, curr) => acc == 0 ? curr.length : (curr.length == 0 ? acc : Math.min(acc, curr.length)), 0);
     let i = 0;
@@ -564,51 +927,107 @@ export function reduceSelector(selector: string[][]) {
         if (!match) {
             break;
         }
+
         optimized.push(item);
     }
+
+    while (optimized.length > 0) {
+
+        const last = <string>optimized.at(-1);
+
+        if ((last == ' ' || combinators.includes(<string>last))) {
+
+            optimized.pop();
+            continue;
+        }
+
+        break;
+    }
+
     selector.forEach((selector) => selector.splice(0, optimized.length));
+
     // combinator
     if (combinators.includes(<string>optimized.at(-1))) {
         const combinator = <string>optimized.pop();
         selector.forEach(selector => selector.unshift(combinator));
     }
-    if (optimized.at(-1) == ' ') {
-        optimized.pop();
-    }
+
     let reducible = optimized.length == 1;
+
+    if (optimized[0] == '&' && optimized[1] == ' ') {
+
+        optimized.splice(0, 2);
+    }
+
     if (optimized.length == 0 ||
-        optimized[0].charAt(0) == '&' ||
-        selector.length == 1) {
+        (optimized[0].charAt(0) == '&' ||
+            selector.length == 1)) {
         return {
             match: false,
             optimized,
-            selector,
-            reducible: selector.length > 1 && selector.every((selector) => !['>', '+', '~'].includes(selector[0]))
+            selector: selector.map(selector => selector[0] == '&' && selector[1] == ' ' ? selector.slice(2) : selector),
+            reducible: selector.length > 1 && selector.every((selector) => !combinators.includes(selector[0]))
         };
     }
+
     return {
         match: true,
         optimized,
         selector: selector.reduce((acc, curr) => {
+
+            let hasCompound = true;
+
+            if (hasCompound && curr.length > 0) {
+
+                hasCompound = !['&'].concat(combinators).includes(curr[0].charAt(0));
+            }
+
             // @ts-ignore
-            if (curr.length > 0 && curr[0] == ' ') {
-                curr.shift();
+            if (hasCompound && curr[0] == ' ') {
+
+                hasCompound = false;
+                curr.unshift('&');
             }
+
             if (curr.length == 0) {
                 curr.push('&');
+                hasCompound = false;
             }
+
             if (reducible) {
                 const chr = curr[0].charAt(0);
                 // @ts-ignore
                 reducible = chr == '.' || chr == ':' || isIdentStart(chr.codePointAt(0));
             }
-            acc.push(curr);
+
+            acc.push(hasCompound ? ['&'].concat(curr) : curr);
             return acc;
         }, <string[][]>[]),
         reducible: selector.every((selector) => !['>', '+', '~', '&'].includes(selector[0]))
     };
 }
-function reducer(acc: string[], curr: string[]) {
+
+function reducer(acc: string[], curr: string[], index: number, array: string[][]) {
+
+    // trim :is()
+    if (array.length == 1 && array[0][0] == ':is(' && array[0].at(-1) == ')') {
+
+        curr = curr.slice(1, -1);
+    }
+
+    if (curr[0] == '&') {
+
+        if (curr[1] == ' ') {
+
+            curr.splice(0, 2);
+        }
+
+        else if (combinators.includes(curr[1])) {
+
+            curr.splice(0, 1);
+        }
+    }
+
     acc.push(curr.join(''));
     return acc;
 }
diff --git a/src/lib/parser/parse.ts b/src/lib/parser/parse.ts
index b9aed28..51e8c45 100644
--- a/src/lib/parser/parse.ts
+++ b/src/lib/parser/parse.ts
@@ -203,6 +203,7 @@ export async function parse(iterator: string, opt: ParserOptions = {}): Promise<
         }
     }
     async function parseNode(tokens: Token[]) {
+
         let i: number;
         let loc: Location;
 
@@ -888,15 +889,16 @@ export async function parse(iterator: string, opt: ParserOptions = {}): Promise<
 
             case '>':
 
+                if (buffer !== '') {
+                    pushToken(getType(buffer));
+                    buffer = '';
+                }
+
                 if (tokens[tokens.length - 1]?.typ == 'Whitespace') {
 
                     tokens.pop();
                 }
 
-                if (buffer !== '') {
-                    pushToken(getType(buffer));
-                    buffer = '';
-                }
                 pushToken({ typ: 'Gt' });
                 consumeWhiteSpace();
                 break;
@@ -1060,6 +1062,7 @@ export async function parse(iterator: string, opt: ParserOptions = {}): Promise<
                 pushToken(getBlockType(value));
                 let node = null;
                 if (value == '{' || value == ';') {
+
                     node = await parseNode(tokens);
                     if (node != null) {
                         stack.push(node);
@@ -1154,6 +1157,7 @@ function parseTokens(tokens: Token[], nodeType: NodeType, options: ParseTokenOpt
                     tokens[i + 1].typ = 'Pseudo-class';
                 }
                 if (typ == 'Func' || typ == 'Iden') {
+
                     tokens.splice(i, 1);
                     i--;
                     continue;
@@ -1217,6 +1221,7 @@ function parseTokens(tokens: Token[], nodeType: NodeType, options: ParseTokenOpt
                             (<PseudoClassFunctionToken>tokens[k + 1]).val = ':' + (<PseudoClassFunctionToken>tokens[k + 1]).val;
                         }
                         if (typ == 'Func' || typ == 'Iden') {
+
                             tokens.splice(k, 1);
                             k--;
                             continue;
@@ -1233,6 +1238,7 @@ function parseTokens(tokens: Token[], nodeType: NodeType, options: ParseTokenOpt
                     break;
                 }
             }
+
             // @ts-ignore
             t.chi = tokens.splice(i + 1, k - i);
             // @ts-ignore
@@ -1262,11 +1268,13 @@ function parseTokens(tokens: Token[], nodeType: NodeType, options: ParseTokenOpt
                         if (t.chi[m].typ == 'Literal') {
                             // @ts-ignore
                             if (t.chi[m + 1]?.typ == 'Whitespace') {
+
                                 // @ts-ignore
                                 t.chi.splice(m + 1, 1);
                             }
                             // @ts-ignore
                             if (t.chi[m - 1]?.typ == 'Whitespace') {
+
                                 // @ts-ignore
                                 t.chi.splice(m - 1, 1);
                                 m--;
@@ -1307,6 +1315,7 @@ function parseTokens(tokens: Token[], nodeType: NodeType, options: ParseTokenOpt
                         (i == 0 &&
                             (tokens[i + 1]?.typ == 'Comma' || tokens.length == i + 1)) ||
                         (tokens[i - 1]?.typ == 'Comma' && (tokens[i + 1]?.typ == 'Comma' || tokens.length == i + 1))) {
+
                         tokens.splice(i, 1, ...t.chi);
                         i = Math.max(0, i - t.chi.length);
                     }
diff --git a/test/specs/block.spec.js b/test/specs/block.spec.js
index bc4f800..ae81135 100644
--- a/test/specs/block.spec.js
+++ b/test/specs/block.spec.js
@@ -7,18 +7,23 @@ import { readFileSync } from 'fs';
 
 const dir = dirname(new URL(import.meta.url).pathname) + '/../files';
 describe('parse block', function () {
+
     it('parse file', function () {
         return readFile(`${dir}/css/smalli.css`, { encoding: 'utf-8' }).then(file => transform(file).then(result => f(result.ast).deep.equals(JSON.parse((readFileSync(dir + '/json/smalli.json')).toString()))));
     });
+
     it('parse file #2', function () {
         return readFile(`${dir}/css/small.css`, { encoding: 'utf-8' }).then(file => transform(file).then(result => f(result.ast).deep.equals(JSON.parse((readFileSync(dir + '/json/small.json')).toString()))));
     });
+
     it('parse file #3', function () {
         readFile(`${dir}/css/invalid-1.css`, { encoding: 'utf-8' }).then(file => transform(file).then(result => f(result.ast).deep.equals(JSON.parse((readFileSync(dir + '/json/invalid-1.json')).toString()))));
     });
+
     it('parse file #4', function () {
         return readFile(`${dir}/css/invalid-2.css`, { encoding: 'utf-8' }).then(file => transform(file).then(result => f(result.ast).deep.equals(JSON.parse((readFileSync(dir + '/json/invalid-2.json')).toString()))));
     });
+
     it('similar rules #5', function () {
         const file = `
 .clear {
@@ -35,6 +40,7 @@ describe('parse block', function () {
             compress: true
         }).then(result => f(result.code).equals(`.clear,.clearfix:before{width:0;height:0}`));
     });
+
     it('similar rules #5', function () {
         const file = `
 .clear {
@@ -51,6 +57,7 @@ describe('parse block', function () {
             compress: true
         }).then(result => f(result.code).equals(`.clear,.clearfix:before{width:0;height:0}`));
     });
+
     it('duplicated selector components #6', function () {
         const file = `
 
@@ -64,6 +71,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`.test input[type=text],a{border-color:gold red}`));
     });
+
     it('merge selectors #7', function () {
         const file = `
 
@@ -106,6 +114,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`.blockquote{margin-bottom:1rem;font-size:1.25rem}.blockquote>:last-child{margin-bottom:0}.blockquote-footer{margin-top:-1rem;margin-bottom:1rem;font-size:.875em;color:#6c757d}.blockquote-footer::before{content:"— "}.img-fluid,.img-thumbnail{max-width:100%;height:auto}.img-thumbnail{padding:.25rem;background-color:var(--bs-body-bg);border:var(--bs-border-width) solid var(--bs-border-color);border-radius:var(--bs-border-radius)}`));
     });
+
     it('merge selectors #8', function () {
         const file = `
 
@@ -119,6 +128,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`.nav-pills:is(.nav-link.active,.show>.nav-link){color:var(--bs-nav-pills-link-active-color);background-color:var(--bs-nav-pills-link-active-bg)}`));
     });
+
     it('merge selectors #9', function () {
         const file = `
 
@@ -131,6 +141,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`.card{--bs-card-inner-border-radius:calc(var(--bs-border-radius) - (var(--bs-border-width)))}`));
     });
+
     it('merge selectors #10', function () {
         const file = `
 
@@ -145,6 +156,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`@media (max-width:575.98px) and (prefers-reduced-motion:reduce){.offcanvas-sm{transition:none}}`));
     });
+
     it('merge selectors #11', function () {
         const file = `
 
@@ -158,6 +170,7 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`:root:is(.fa-flip-both,.fa-flip-horizontal,.fa-flip-vertical,.fa-rotate-180,.fa-rotate-270,.fa-rotate-90){-webkit-filter:none;filter:none}`));
     });
+
     it('merge selectors #12', function () {
         const file = `
 .bs-popover-auto[data-popper-placement^=top]>.popover-arrow,.bs-popover-top>.popover-arrow{bottom:calc(-1 * (var(--bs-popover-arrow-height)) - var(--bs-popover-border-width))}
@@ -167,4 +180,22 @@ border-left-color: red;
             compress: true
         }).then(result => f(result.code).equals(`.bs-popover-auto[data-popper-placement^=top]>.popover-arrow,.bs-popover-top>.popover-arrow{bottom:calc(-1 * (var(--bs-popover-arrow-height)) - var(--bs-popover-border-width))}`));
     });
+
+    it('merge selectors #13', function () {
+        const file = `
+
+abbr[title], abbr[data-original-title], abbr>[data-original-title] {
+    text-decoration: underline dotted;
+    -webkit-text-decoration: underline dotted;
+    cursor: help;
+    border-bottom: 0;
+    -webkit-text-decoration-skip-ink: none;
+    text-decoration-skip-ink: none
+}
+
+`;
+        return transform(file, {
+            compress: true
+        }).then(result => f(result.code).equals(`abbr:is([title],[data-original-title],abbr>[data-original-title]){text-decoration:underline dotted;-webkit-text-decoration:underline dotted;cursor:help;border-bottom:0;-webkit-text-decoration-skip-ink:none;text-decoration-skip-ink:none}`));
+    });
 });
diff --git a/test/specs/import.spec.js b/test/specs/import.spec.js
index c144440..6264a93 100644
--- a/test/specs/import.spec.js
+++ b/test/specs/import.spec.js
@@ -20,6 +20,6 @@ describe('process import', function () {
         return transform(atRule, {
             compress: true,
             resolveImport: true
-        }).then((result) => f(result.code).equals(`p{color:#8133cc26}abbr[title],abbr[data-original-title]{text-decoration:underline dotted;-webkit-text-decoration:underline dotted;cursor:help;border-bottom:0;-webkit-text-decoration-skip-ink:none;text-decoration-skip-ink:none}`));
+        }).then((result) => f(result.code).equals(`p{color:#8133cc26}abbr:is([title],[data-original-title]){text-decoration:underline dotted;-webkit-text-decoration:underline dotted;cursor:help;border-bottom:0;-webkit-text-decoration-skip-ink:none;text-decoration-skip-ink:none}`));
     });
 });
diff --git a/test/specs/nesting.spec.js b/test/specs/nesting.spec.js
new file mode 100644
index 0000000..9a6f598
--- /dev/null
+++ b/test/specs/nesting.spec.js
@@ -0,0 +1,366 @@
+/* generate from test/specs/nesting.spec.ts */
+import {expect as f} from '../../node_modules/@esm-bundle/chai/esm/chai.js';
+import {transform} from '../../dist/node/index.js';
+
+describe('CSS Nesting', function () {
+    it('nesting #1', function () {
+        const nesting1 = `
+.nesting {
+  color: hotpink;
+}
+
+.nesting > .is {
+  color: rebeccapurple;
+}
+
+.nesting > .is > .awesome {
+  color: deeppink;
+}
+`;
+        return transform(nesting1, {
+            compress: true,
+            nestingRules: true
+        }).then((result) => f(result.code).equals(`.nesting{color:hotpink;>.is{color:#639;>.awesome{color:#ff1493}}}`));
+    });
+
+    it('nesting #2', function () {
+        const nesting2 = `
+.nav-link:focus, .nav-link:hover {
+    color: var(--bs-nav-link-hover-color)
+}
+
+`;
+        return transform(nesting2, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.nav-link{&:focus,&:hover{color:var(--bs-nav-link-hover-color)}}`));
+    });
+    it('nesting #3', function () {
+        const nesting3 = `
+.nav-link:focus, .nav-link:hover {
+    color: var(--bs-nav-link-hover-color)
+}
+
+.nav-link:focus-visible {
+    outline: 0;
+    box-shadow: 0 0 0 .25rem rgba(13, 110, 253, .25)
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.nav-link{&:focus,&:hover{color:var(--bs-nav-link-hover-color)}&:focus-visible{outline:0;box-shadow:0 0 0 .25rem #0d6efd40}}`));
+    });
+    it('nesting #4', function () {
+        const nesting3 = `
+
+.nav-link:focus, .nav-link:hover {
+    color: var(--bs-nav-link-hover-color)
+}
+
+.nav-link:focus-visible {
+    outline: 0;
+    box-shadow: 0 0 0 .25rem rgba(13, 110, 253, .25)
+}
+
+.nav-link.disabled {
+    color: var(--bs-nav-link-disabled-color);
+    pointer-events: none;
+    cursor: default
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.nav-link{&:focus,&:hover{color:var(--bs-nav-link-hover-color)}&:focus-visible{outline:0;box-shadow:0 0 0 .25rem #0d6efd40}&.disabled{color:var(--bs-nav-link-disabled-color);pointer-events:none;cursor:default}}`));
+    });
+    it('nesting #5', function () {
+        const nesting3 = `
+
+.nav-link:focus, .nav-link:hover {
+    color: var(--bs-nav-link-hover-color)
+}
+
+.nav-link:focus-visible {
+    outline: 0;
+    box-shadow: 0 0 0 .25rem rgba(13, 110, 253, .25)
+}
+
+.nav-link.disabled {
+    color: var(--bs-nav-link-disabled-color);
+    pointer-events: none;
+    cursor: default
+}
+
+.nav-link:disabled {
+    color: var(--bs-nav-link-disabled-color);
+    pointer-events: none;
+    cursor: default
+}
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.nav-link{&:focus,&:hover{color:var(--bs-nav-link-hover-color)}&:focus-visible{outline:0;box-shadow:0 0 0 .25rem #0d6efd40}&.disabled,&:disabled{color:var(--bs-nav-link-disabled-color);pointer-events:none;cursor:default}}`));
+    });
+    it('nesting #6', function () {
+        const nesting3 = `
+
+.form-floating > .form-control, .form-floating > .form-control-plaintext, .form-floating > .form-select {
+    height: calc(3.5rem + calc(var(--bs-border-width) * 2));
+}
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.form-floating{>.form-control,>.form-control-plaintext,>.form-select{height:calc(3.5rem + calc(var(--bs-border-width) * 2))}}`));
+    });
+    it('nesting #7', function () {
+        const nesting3 = `
+
+.form-floating {
+    position: relative
+}
+
+.form-floating > .form-control, .form-floating > .form-control-plaintext, .form-floating > .form-select {
+    height: calc(3.5rem + calc(var(--bs-border-width) * 2));
+    min-height: calc(3.5rem + calc(var(--bs-border-width) * 2));
+    line-height: 1.25;
+    z-index: 2;
+    white-space: nowrap;
+}
+
+.form-floating > label {
+    position: absolute;
+    top: 0;
+    left: 0;
+    z-index: 2;
+    height: 100%;
+    padding: 1rem .75rem;
+    overflow: hidden;
+    text-align: start;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+    pointer-events: none;
+    border: var(--bs-border-width) solid transparent;
+    transform-origin: 0 0;
+    transition: opacity .1s ease-in-out, transform .1s ease-in-out
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.form-floating{position:relative;>.form-control,>.form-control-plaintext,>.form-select{height:calc(3.5rem + calc(var(--bs-border-width) * 2));min-height:calc(3.5rem + calc(var(--bs-border-width) * 2));line-height:1.25;z-index:2;white-space:nowrap}>label{position:absolute;top:0;left:0;z-index:2;height:100%;padding:1rem .75rem;overflow:hidden;text-align:start;text-overflow:ellipsis;white-space:nowrap;pointer-events:none;border:var(--bs-border-width) solid #0000;transform-origin:0 0;transition:opacity .1s ease-in-out,transform .1s ease-in-out}}`));
+    });
+
+    it('nesting #8', function () {
+        const nesting3 = `
+
+.card {
+    --bs-card-spacer-y: 1rem;
+    --bs-card-spacer-x: 1rem;
+    --bs-card-title-spacer-y: 0.5rem;
+    --bs-card-title-color: ;
+    --bs-card-subtitle-color: ;
+    --bs-card-border-width: var(--bs-border-width);
+    --bs-card-border-color: var(--bs-border-color-translucent);
+    --bs-card-border-radius: var(--bs-border-radius);
+    --bs-card-box-shadow: ;
+    --bs-card-inner-border-radius: calc(var(--bs-border-radius) - (var(--bs-border-width)));
+    --bs-card-cap-padding-y: 0.5rem;
+    --bs-card-cap-padding-x: 1rem;
+    --bs-card-cap-bg: rgba(var(--bs-body-color-rgb), 0.03);
+    --bs-card-cap-color: ;
+    --bs-card-height: ;
+    --bs-card-color: ;
+    --bs-card-bg: var(--bs-body-bg);
+    --bs-card-img-overlay-padding: 1rem;
+    --bs-card-group-margin: 0.75rem;
+    position: relative;
+    display: flex;
+    flex-direction: column;
+    min-width: 0;
+    height: var(--bs-card-height);
+    color: var(--bs-body-color);
+    word-wrap: break-word;
+    background-color: var(--bs-card-bg);
+    background-clip: border-box;
+    border: var(--bs-card-border-width) solid var(--bs-card-border-color);
+    border-radius: var(--bs-card-border-radius)
+}
+
+.card > hr {
+    margin-right: 0;
+    margin-left: 0
+}
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.card{--bs-card-spacer-y:1rem;--bs-card-spacer-x:1rem;--bs-card-title-spacer-y:.5rem;--bs-card-border-width:var(--bs-border-width);--bs-card-border-color:var(--bs-border-color-translucent);--bs-card-border-radius:var(--bs-border-radius);--bs-card-inner-border-radius:calc(var(--bs-border-radius) - (var(--bs-border-width)));--bs-card-cap-padding-y:.5rem;--bs-card-cap-padding-x:1rem;--bs-card-cap-bg:rgba(var(--bs-body-color-rgb),.03);--bs-card-bg:var(--bs-body-bg);--bs-card-img-overlay-padding:1rem;--bs-card-group-margin:.75rem;position:relative;display:flex;flex-direction:column;min-width:0;height:var(--bs-card-height);color:var(--bs-body-color);word-wrap:break-word;background-color:var(--bs-card-bg);background-clip:border-box;border:var(--bs-card-border-width) solid var(--bs-card-border-color);border-radius:var(--bs-card-border-radius);>hr{margin-right:0;margin-left:0}}`));
+    });
+    it('nesting #9', function () {
+        const nesting3 = `
+.tab-content{>.tab-pane{display:none}>.active{display:block}}.navbar{--bs-navbar-padding-x:0;--bs-navbar-padding-y:.5rem;--bs-navbar-color:rgba(var(--bs-emphasis-color-rgb),.65);--bs-navbar-hover-color:rgba(var(--bs-emphasis-color-rgb),.8);--bs-navbar-disabled-color:rgba(var(--bs-emphasis-color-rgb),.3);--bs-navbar-active-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-brand-padding-y:.3125rem;--bs-navbar-brand-margin-end:1rem;--bs-navbar-brand-font-size:1.25rem;--bs-navbar-brand-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-brand-hover-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-nav-link-padding-x:.5rem;--bs-navbar-toggler-padding-y:.25rem;--bs-navbar-toggler-padding-x:.75rem;--bs-navbar-toggler-font-size:1.25rem;--bs-navbar-toggler-icon-bg:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba%2833, 37, 41, 0.75%29' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");--bs-navbar-toggler-border-color:rgba(var(--bs-emphasis-color-rgb),.15);--bs-navbar-toggler-border-radius:var(--bs-border-radius);--bs-navbar-toggler-focus-width:.25rem;--bs-navbar-toggler-transition:box-shadow .15s ease-in-out;position:relative;display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;padding:var(--bs-navbar-padding-y) var(--bs-navbar-padding-x);>.container,>.container-fluid,>.container-lg,>.container-md,>.container-sm,>.container-xl,>.container-xxl{display:flex;flex-wrap:inherit;align-items:center;justify-content:space-between}}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.tab-content{>.tab-pane{display:none}>.active{display:block}}.navbar{--bs-navbar-padding-x:0;--bs-navbar-padding-y:.5rem;--bs-navbar-color:rgba(var(--bs-emphasis-color-rgb),.65);--bs-navbar-hover-color:rgba(var(--bs-emphasis-color-rgb),.8);--bs-navbar-disabled-color:rgba(var(--bs-emphasis-color-rgb),.3);--bs-navbar-active-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-brand-padding-y:.3125rem;--bs-navbar-brand-margin-end:1rem;--bs-navbar-brand-font-size:1.25rem;--bs-navbar-brand-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-brand-hover-color:rgba(var(--bs-emphasis-color-rgb),1);--bs-navbar-nav-link-padding-x:.5rem;--bs-navbar-toggler-padding-y:.25rem;--bs-navbar-toggler-padding-x:.75rem;--bs-navbar-toggler-font-size:1.25rem;--bs-navbar-toggler-icon-bg:url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba%2833, 37, 41, 0.75%29' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");--bs-navbar-toggler-border-color:rgba(var(--bs-emphasis-color-rgb),.15);--bs-navbar-toggler-border-radius:var(--bs-border-radius);--bs-navbar-toggler-focus-width:.25rem;--bs-navbar-toggler-transition:box-shadow .15s ease-in-out;position:relative;display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;padding:var(--bs-navbar-padding-y) var(--bs-navbar-padding-x);>.container,>.container-fluid,>.container-lg,>.container-md,>.container-sm,>.container-xl,>.container-xxl{display:flex;flex-wrap:inherit;align-items:center;justify-content:space-between}}`));
+    });
+
+    it('nesting #10', function () {
+        const nesting3 = `
+
+
+.navbar-text {
+    padding-top: .5rem;
+    padding-bottom: .5rem;
+    color: var(--bs-navbar-color)
+}
+
+.navbar-text a, .navbar-text a:focus, .navbar-text a:hover {
+    color: var(--bs-navbar-active-color)
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.navbar-text{padding-top:.5rem;padding-bottom:.5rem;color:var(--bs-navbar-color);a{&,&:focus,&:hover{color:var(--bs-navbar-active-color)}}}`));
+    });
+
+    it('nesting #11', function () {
+        const nesting3 = `
+
+.table-bordered > :not(caption) > * {
+    border-width: var(--bs-border-width) 0
+}
+
+.table-bordered > :not(caption) > * > * {
+    border-width: 0 var(--bs-border-width)
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.table-bordered>:not(caption)>*{border-width:var(--bs-border-width) 0;>*{border-width:0 var(--bs-border-width)}}`));
+    });
+
+
+    it('nesting #12', function () {
+        const nesting3 = `
+
+.dropdown-item {
+    display: block;
+    width: 100%;
+    padding: var(--bs-dropdown-item-padding-y) var(--bs-dropdown-item-padding-x);
+    clear: both;
+    font-weight: 400;
+    color: var(--bs-dropdown-link-color);
+    text-align: inherit;
+    text-decoration: none;
+    white-space: nowrap;
+    background-color: transparent;
+    border: 0;
+    border-radius: var(--bs-dropdown-item-border-radius, 0)
+}
+
+.dropdown-item:focus, .dropdown-item:hover {
+    color: var(--bs-dropdown-link-hover-color);
+    background-color: var(--bs-dropdown-link-hover-bg)
+}
+
+.dropdown-item.active, .dropdown-item:active {
+    color: var(--bs-dropdown-link-active-color);
+    text-decoration: none;
+    background-color: var(--bs-dropdown-link-active-bg)
+}
+
+.dropdown-item.disabled, .dropdown-item:disabled {
+    color: var(--bs-dropdown-link-disabled-color);
+    pointer-events: none;
+    background-color: transparent
+}
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.dropdown-item{display:block;width:100%;padding:var(--bs-dropdown-item-padding-y) var(--bs-dropdown-item-padding-x);clear:both;font-weight:400;color:var(--bs-dropdown-link-color);text-align:inherit;text-decoration:none;white-space:nowrap;background-color:#0000;border:0;border-radius:var(--bs-dropdown-item-border-radius,0);&:focus,&:hover{color:var(--bs-dropdown-link-hover-color);background-color:var(--bs-dropdown-link-hover-bg)}&.active,&:active{color:var(--bs-dropdown-link-active-color);text-decoration:none;background-color:var(--bs-dropdown-link-active-bg)}&.disabled,&:disabled{color:var(--bs-dropdown-link-disabled-color);pointer-events:none;background-color:#0000}}`));
+    });
+
+    it('nesting #13', function () {
+        const nesting3 = `
+
+[data-bs-theme=dark] .carousel .carousel-control-next-icon, [data-bs-theme=dark] .carousel .carousel-control-prev-icon, [data-bs-theme=dark].carousel .carousel-control-next-icon, [data-bs-theme=dark].carousel .carousel-control-prev-icon {
+    filter: invert(1) grayscale(100)
+}
+
+[data-bs-theme=dark] .carousel .carousel-indicators [data-bs-target], [data-bs-theme=dark].carousel .carousel-indicators [data-bs-target] {
+    background-color: #000
+}
+
+[data-bs-theme=dark] .carousel .carousel-caption, [data-bs-theme=dark].carousel .carousel-caption {
+    color: #000
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`[data-bs-theme=dark]{.carousel .carousel-control-next-icon,.carousel .carousel-control-prev-icon,&.carousel .carousel-control-next-icon,&.carousel .carousel-control-prev-icon{filter:invert(1)grayscale(100)}.carousel .carousel-indicators [data-bs-target],&.carousel .carousel-indicators [data-bs-target]{background-color:#000}.carousel .carousel-caption,&.carousel .carousel-caption{color:#000}}`));
+    });
+
+    it('nesting #14', function () {
+        const nesting3 = `
+
+.demo.lg.triangle {
+    opacity: .25;
+    filter: blur(25px);
+    }
+  .demo.lg.circle {
+    opacity: .25;
+    filter: blur(25px);
+  }
+}
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.demo.lg{&.triangle,&.circle{opacity:.25;filter:blur(25px)}}`));
+    });
+
+    it('nesting #15', function () {
+        const nesting3 = `
+
+.nav-pills .nav-link.active, .nav-pills .show>.nav-link {
+    color: var(--bs-nav-pills-link-active-color);
+    background-color: var(--bs-nav-pills-link-active-bg)
+}
+
+`;
+        return transform(nesting3, {
+            compress: true,
+            nestingRules: true,
+            resolveImport: true
+        }).then((result) => f(result.code).equals(`.nav-pills{.nav-link.active,.show>.nav-link{color:var(--bs-nav-pills-link-active-color);background-color:var(--bs-nav-pills-link-active-bg)}}`));
+    });
+});