diff --git a/playground/nitro.config.ts b/playground/nitro.config.ts
index a763adbd67..41776090ae 100644
--- a/playground/nitro.config.ts
+++ b/playground/nitro.config.ts
@@ -1 +1,5 @@
-export default defineNitroConfig({});
\ No newline at end of file
+export default defineNitroConfig({
+    experimental: {
+        openAPI: true,
+    }
+});
diff --git a/src/runtime/routes/scalar.ts b/src/runtime/routes/scalar.ts
index 9a07871caf..5d0fef3680 100644
--- a/src/runtime/routes/scalar.ts
+++ b/src/runtime/routes/scalar.ts
@@ -13,6 +13,9 @@ export default eventHandler((event) => {
         <meta name="viewport" content="width=device-width, initial-scale=1" />
         <meta name="description" content="${title}" />
         <title>${title}</title>
+        <style>
+          ${customTheme}
+        </style>
       </head>
       <body>
         <script
@@ -27,3 +30,158 @@ export default eventHandler((event) => {
 function html(str, ...args) {
   return String.raw(str, ...args);
 }
+
+const customTheme =
+  `/* basic theme */
+  .light-mode,
+  .light-mode .dark-mode {
+    --theme-background-1: #fff;
+    --theme-background-2: #fafafa;
+    --theme-background-3: rgb(245 245 245);
+
+    --theme-color-1: #2a2f45;
+    --theme-color-2: #757575;
+    --theme-color-3: #8e8e8e;
+
+    --theme-color-accent: #ef4444;
+    --theme-background-accent: transparent;
+
+    --theme-border-color: rgba(0, 0, 0, 0.1);
+  }
+  .dark-mode {
+    --theme-background-1: #171717;
+    --theme-background-2: #262626;
+    --theme-background-3: #2e2e2e;
+
+    --theme-color-1: rgba(255, 255, 255, 0.9);
+    --theme-color-2: rgba(255, 255, 255, 0.62);
+    --theme-color-3: rgba(255, 255, 255, 0.44);
+
+    --theme-color-accent: #f87171;
+    --theme-background-accent: transparent;
+
+    --theme-border-color: rgba(255, 255, 255, 0.1);
+  }
+
+  /* Document Sidebar */
+  .light-mode .t-doc__sidebar,
+  .dark-mode .t-doc__sidebar {
+    --sidebar-background-1: var(--theme-background-1);
+    --sidebar-color-1: var(--theme-color-1);
+    --sidebar-color-2: var(--theme-color-2);
+    --sidebar-border-color: var(--theme-border-color);
+
+    --sidebar-item-hover-background: transparent;
+    --sidebar-item-hover-color: var(--sidebar-color-1);
+
+    --sidebar-item-active-background: var(--theme-background-accent);
+    --sidebar-color-active: var(--theme-color-accent);
+
+    --sidebar-search-background: transparent;
+    --sidebar-search-color: var(--theme-color-3);
+    --sidebar-search-border-color: var(--theme-border-color);
+  }
+
+  /* advanced */
+  .light-mode .dark-mode,
+  .light-mode {
+    --theme-color-green: #91b859;
+    --theme-color-red: #e53935;
+    --theme-color-yellow: #e2931d;
+    --theme-color-blue: #6182b8;
+    --theme-color-orange: #f76d47;
+    --theme-color-purple: #9c3eda;
+  }
+  .dark-mode {
+    --theme-color-green: #c3e88d;
+    --theme-color-red: #f07178;
+    --theme-color-yellow: #ffcb6b;
+    --theme-color-blue: #82aaff;
+    --theme-color-orange: #f78c6c;
+    --theme-color-purple: #c792ea;
+  }
+  /* custom-theme */
+  .section-container:nth-of-type(2)
+    ~ .section-container
+    .scalar-card
+    .scalar-card-header {
+    --theme-background-2: var(--theme-background-1) !important;
+  }
+  .section-flare {
+    width: 100%;
+    height: 100%;
+    position: absolute;
+    top: 0;
+    left: 0;
+    animation: spin 39s linear infinite;
+    transition: all 0.3s ease-in-out;
+    opacity: 1;
+  }
+  .section-flare-item:nth-of-type(1),
+  .section-flare-item:nth-of-type(2),
+  .section-flare-item:nth-of-type(3) {
+    content: "";
+    width: 1000px;
+    height: 1000px;
+    position: absolute;
+    top: 0;
+    right: 0;
+    border-radius: 50%;
+    background: var(--default-theme-background-1);
+    display: block;
+    opacity: 1;
+    filter: blur(48px);
+    -webkit-backface-visibility: hidden;
+    -webkit-perspective: 1000;
+    -webkit-transform: translate3d(0, 0, 0);
+    -webkit-transform: translateZ(0);
+    perspective: 1000;
+    transform: translate3d(0, 0, 0);
+    transform: translateZ(0);
+  }
+  .section-flare-item:nth-of-type(2) {
+    top: initial;
+    right: initial;
+    background: #ef4444;
+    width: 700px;
+    height: 700px;
+    opacity: 0.3;
+    animation: sectionflare 37s linear infinite;
+  }
+  .section-flare-item:nth-of-type(1) {
+    top: initial;
+    right: initial;
+    bottom: 0;
+    left: -20px;
+    background: #ef4444;
+    width: 500px;
+    height: 500px;
+    opacity: 0.3;
+    animation: sectionflare2 38s linear infinite;
+  }
+  @keyframes sectionflare {
+    0%,
+    100% {
+      transform: translate3d(0, 0, 0);
+    }
+    50% {
+      transform: translate3d(525px, 525px, 0);
+    }
+  }
+  @keyframes sectionflare2 {
+    0%,
+    100% {
+      transform: translate3d(700px, 700px, 0);
+    }
+    50% {
+      transform: translate3d(0, 0, 0);
+    }
+  }
+  @keyframes spin {
+    100% {
+      transform: rotate(360deg);
+    }
+  }
+  .section-container:nth-of-type(2) {
+    overflow: hidden;
+  }`
