diff --git a/theme/css/chrome.css b/theme/css/chrome.css
deleted file mode 100644
index cad7d5f459b1..000000000000
--- a/theme/css/chrome.css
+++ /dev/null
@@ -1,681 +0,0 @@
-/* CSS for UI elements (a.k.a. chrome) */
-
-html {
-  scrollbar-color: var(--scrollbar) var(--bg);
-}
-#searchresults a,
-.content a:link,
-a:visited,
-a > .hljs {
-  color: var(--links);
-}
-
-/*
-    body-container is necessary because mobile browsers don't seem to like
-    overflow-x on the body tag when there is a <meta name="viewport"> tag.
-*/
-#body-container {
-  /*
-        This is used when the sidebar pushes the body content off the side of
-        the screen on small screens. Without it, dragging on mobile Safari
-        will want to reposition the viewport in a weird way.
-    */
-  overflow-x: clip;
-}
-
-/* Menu Bar */
-
-#menu-bar,
-#menu-bar-hover-placeholder {
-  z-index: 101;
-  margin: auto calc(0px - var(--page-padding));
-}
-#menu-bar {
-  position: relative;
-  display: flex;
-  flex-wrap: wrap;
-  background-color: var(--bg);
-  border-block-end-color: var(--bg);
-  border-block-end-width: 1px;
-  border-block-end-style: solid;
-}
-#menu-bar.sticky,
-#menu-bar-hover-placeholder:hover + #menu-bar,
-#menu-bar:hover,
-html.sidebar-visible #menu-bar {
-  position: -webkit-sticky;
-  position: sticky;
-  top: 0 !important;
-}
-#menu-bar-hover-placeholder {
-  position: sticky;
-  position: -webkit-sticky;
-  top: 0;
-  height: var(--menu-bar-height);
-}
-#menu-bar.bordered {
-  border-block-end-color: var(--table-border-color);
-}
-#menu-bar i,
-#menu-bar .icon-button {
-  position: relative;
-  padding: 0 8px;
-  z-index: 10;
-  line-height: var(--menu-bar-height);
-  cursor: pointer;
-  transition: color 0.5s;
-}
-@media only screen and (max-width: 420px) {
-  #menu-bar i,
-  #menu-bar .icon-button {
-    padding: 0 5px;
-  }
-}
-
-.icon-button {
-  border: none;
-  background: none;
-  padding: 0;
-  color: inherit;
-}
-.icon-button i {
-  margin: 0;
-}
-
-.right-buttons {
-  margin: 0 15px;
-}
-.right-buttons a {
-  text-decoration: none;
-}
-
-.left-buttons {
-  display: flex;
-  margin: 0 5px;
-}
-html:not(.js) .left-buttons button {
-  display: none;
-}
-
-.menu-title {
-  display: inline-block;
-  font-weight: 200;
-  font-size: 2.4rem;
-  line-height: var(--menu-bar-height);
-  text-align: center;
-  margin: 0;
-  flex: 1;
-  white-space: nowrap;
-  overflow: hidden;
-  text-overflow: ellipsis;
-}
-.menu-title {
-  cursor: pointer;
-}
-
-.menu-bar,
-.menu-bar:visited,
-.nav-chapters,
-.nav-chapters:visited,
-.mobile-nav-chapters,
-.mobile-nav-chapters:visited,
-.menu-bar .icon-button,
-.menu-bar a i {
-  color: var(--icons);
-}
-
-.menu-bar i:hover,
-.menu-bar .icon-button:hover,
-.nav-chapters:hover,
-.mobile-nav-chapters i:hover {
-  color: var(--icons-hover);
-}
-
-/* Nav Icons */
-
-.nav-chapters {
-  font-size: 2.5em;
-  text-align: center;
-  text-decoration: none;
-
-  position: fixed;
-  top: 0;
-  bottom: 0;
-  margin: 0;
-  max-width: 150px;
-  min-width: 90px;
-
-  display: flex;
-  justify-content: center;
-  align-content: center;
-  flex-direction: column;
-
-  transition: color 0.5s, background-color 0.5s;
-}
-
-.nav-chapters:hover {
-  text-decoration: none;
-  background-color: var(--theme-hover);
-  transition: background-color 0.15s, color 0.15s;
-}
-
-.nav-wrapper {
-  margin-block-start: 50px;
-  display: none;
-}
-
-.mobile-nav-chapters {
-  font-size: 2.5em;
-  text-align: center;
-  text-decoration: none;
-  width: 90px;
-  border-radius: 5px;
-  background-color: var(--sidebar-bg);
-}
-
-/* Only Firefox supports flow-relative values */
-.previous {
-  float: left;
-}
-[dir="rtl"] .previous {
-  float: right;
-}
-
-/* Only Firefox supports flow-relative values */
-.next {
-  float: right;
-  right: var(--page-padding);
-}
-[dir="rtl"] .next {
-  float: left;
-  right: unset;
-  left: var(--page-padding);
-}
-
-/* Use the correct buttons for RTL layouts*/
-[dir="rtl"] .previous i.fa-angle-left:before {
-  content: "\f105";
-}
-[dir="rtl"] .next i.fa-angle-right:before {
-  content: "\f104";
-}
-
-@media only screen and (max-width: 1080px) {
-  .nav-wide-wrapper {
-    display: none;
-  }
-  .nav-wrapper {
-    display: block;
-  }
-}
-
-/* sidebar-visible */
-@media only screen and (max-width: 1380px) {
-  #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wide-wrapper {
-    display: none;
-  }
-  #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wrapper {
-    display: block;
-  }
-}
-
-/* Inline code */
-
-:not(pre) > .hljs {
-  display: inline;
-  padding: 0.1em 0.3em;
-  border-radius: 3px;
-}
-
-:not(pre):not(a) > .hljs {
-  color: var(--inline-code-color);
-  overflow-x: initial;
-}
-
-a:hover > .hljs {
-  text-decoration: underline;
-}
-
-pre {
-  position: relative;
-}
-pre > .buttons {
-  position: absolute;
-  z-index: 100;
-  right: 0px;
-  top: 2px;
-  margin: 0px;
-  padding: 2px 0px;
-
-  color: var(--sidebar-fg);
-  cursor: pointer;
-  visibility: hidden;
-  opacity: 0;
-  transition: visibility 0.1s linear, opacity 0.1s linear;
-}
-pre:hover > .buttons {
-  visibility: visible;
-  opacity: 1;
-}
-pre > .buttons :hover {
-  color: var(--sidebar-active);
-  border-color: var(--icons-hover);
-  background-color: var(--theme-hover);
-}
-pre > .buttons i {
-  margin-inline-start: 8px;
-}
-pre > .buttons button {
-  cursor: inherit;
-  margin: 0px 5px;
-  padding: 4px 4px 3px 5px;
-  font-size: 23px;
-
-  border-style: solid;
-  border-width: 1px;
-  border-radius: 4px;
-  border-color: var(--icons);
-  background-color: var(--theme-popup-bg);
-  transition: 100ms;
-  transition-property: color, border-color, background-color;
-  color: var(--icons);
-}
-
-pre > .buttons button.clip-button {
-  padding: 2px 4px 0px 6px;
-}
-pre > .buttons button.clip-button::before {
-  /* clipboard image from octicons (https://github.com/primer/octicons/tree/v2.0.0) MIT license
-     */
-  content: url('data:image/svg+xml,<svg width="21" height="20" viewBox="0 0 24 25" \
-xmlns="http://www.w3.org/2000/svg" aria-label="Copy to clipboard">\
-<path d="M18 20h2v3c0 1-1 2-2 2H2c-.998 0-2-1-2-2V5c0-.911.755-1.667 1.667-1.667h5A3.323 3.323 0 \
-0110 0a3.323 3.323 0 013.333 3.333h5C19.245 3.333 20 4.09 20 5v8.333h-2V9H2v14h16v-3zM3 \
-7h14c0-.911-.793-1.667-1.75-1.667H13.5c-.957 0-1.75-.755-1.75-1.666C11.75 2.755 10.957 2 10 \
-2s-1.75.755-1.75 1.667c0 .911-.793 1.666-1.75 1.666H4.75C3.793 5.333 3 6.09 3 7z"/>\
-<path d="M4 19h6v2H4zM12 11H4v2h8zM4 17h4v-2H4zM15 15v-3l-4.5 4.5L15 21v-3l8.027-.032L23 15z"/>\
-</svg>');
-  filter: var(--copy-button-filter);
-}
-pre > .buttons button.clip-button:hover::before {
-  filter: var(--copy-button-filter-hover);
-}
-
-@media (pointer: coarse) {
-  pre > .buttons button {
-    /* On mobile, make it easier to tap buttons. */
-    padding: 0.3rem 1rem;
-  }
-
-  .sidebar-resize-indicator {
-    /* Hide resize indicator on devices with limited accuracy */
-    display: none;
-  }
-}
-pre > code {
-  display: block;
-  padding: 1rem;
-}
-
-/* FIXME: ACE editors overlap their buttons because ACE does absolute
-   positioning within the code block which breaks padding. The only solution I
-   can think of is to move the padding to the outer pre tag (or insert a div
-   wrapper), but that would require fixing a whole bunch of CSS rules.
-*/
-.hljs.ace_editor {
-  padding: 0rem 0rem;
-}
-
-pre > .result {
-  margin-block-start: 10px;
-}
-
-/* Search */
-
-#searchresults a {
-  text-decoration: none;
-}
-
-mark {
-  border-radius: 2px;
-  padding-block-start: 0;
-  padding-block-end: 1px;
-  padding-inline-start: 3px;
-  padding-inline-end: 3px;
-  margin-block-start: 0;
-  margin-block-end: -1px;
-  margin-inline-start: -3px;
-  margin-inline-end: -3px;
-  background-color: var(--search-mark-bg);
-  transition: background-color 300ms linear;
-  cursor: pointer;
-}
-
-mark.fade-out {
-  background-color: rgba(0, 0, 0, 0) !important;
-  cursor: auto;
-}
-
-.searchbar-outer {
-  margin-inline-start: auto;
-  margin-inline-end: auto;
-  max-width: var(--content-max-width);
-}
-
-#searchbar {
-  width: 100%;
-  margin-block-start: 5px;
-  margin-block-end: 0;
-  margin-inline-start: auto;
-  margin-inline-end: auto;
-  padding: 10px 16px;
-  transition: box-shadow 300ms ease-in-out;
-  border: 1px solid var(--searchbar-border-color);
-  border-radius: 3px;
-  background-color: var(--searchbar-bg);
-  color: var(--searchbar-fg);
-}
-#searchbar:focus,
-#searchbar.active {
-  box-shadow: 0 0 3px var(--searchbar-shadow-color);
-}
-
-.searchresults-header {
-  font-weight: bold;
-  font-size: 1em;
-  padding-block-start: 18px;
-  padding-block-end: 0;
-  padding-inline-start: 5px;
-  padding-inline-end: 0;
-  color: var(--searchresults-header-fg);
-}
-
-.searchresults-outer {
-  margin-inline-start: auto;
-  margin-inline-end: auto;
-  max-width: var(--content-max-width);
-  border-block-end: 1px dashed var(--searchresults-border-color);
-}
-
-ul#searchresults {
-  list-style: none;
-  padding-inline-start: 20px;
-}
-ul#searchresults li {
-  margin: 10px 0px;
-  padding: 2px;
-  border-radius: 2px;
-}
-ul#searchresults li.focus {
-  background-color: var(--searchresults-li-bg);
-}
-ul#searchresults span.teaser {
-  display: block;
-  clear: both;
-  margin-block-start: 5px;
-  margin-block-end: 0;
-  margin-inline-start: 20px;
-  margin-inline-end: 0;
-  font-size: 0.8em;
-}
-ul#searchresults span.teaser em {
-  font-weight: bold;
-  font-style: normal;
-}
-
-/* Sidebar */
-
-.sidebar {
-  position: fixed;
-  left: 0;
-  top: 0;
-  bottom: 0;
-  width: var(--sidebar-width);
-  font-size: 0.875em;
-  box-sizing: border-box;
-  -webkit-overflow-scrolling: touch;
-  overscroll-behavior-y: contain;
-  background-color: var(--sidebar-bg);
-  color: var(--sidebar-fg);
-}
-.sidebar-iframe-inner {
-  background-color: var(--sidebar-bg);
-  color: var(--sidebar-fg);
-  padding: 10px 10px;
-  margin: 0;
-  font-size: 1.4rem;
-}
-.sidebar-iframe-outer {
-  border: none;
-  height: 100%;
-  position: absolute;
-  top: 0;
-  bottom: 0;
-  left: 0;
-  right: 0;
-}
-[dir="rtl"] .sidebar {
-  left: unset;
-  right: 0;
-}
-.sidebar-resizing {
-  -moz-user-select: none;
-  -webkit-user-select: none;
-  -ms-user-select: none;
-  user-select: none;
-}
-html:not(.sidebar-resizing) .sidebar {
-  transition: transform 0.3s; /* Animation: slide away */
-}
-.sidebar code {
-  line-height: 2em;
-}
-.sidebar .sidebar-scrollbox {
-  overflow-y: auto;
-  position: absolute;
-  top: 0;
-  bottom: 0;
-  left: 0;
-  right: 0;
-  padding: 10px 10px;
-}
-.sidebar .sidebar-resize-handle {
-  position: absolute;
-  cursor: col-resize;
-  width: 0;
-  right: calc(var(--sidebar-resize-indicator-width) * -1);
-  top: 0;
-  bottom: 0;
-  display: flex;
-  align-items: center;
-}
-
-.sidebar-resize-handle .sidebar-resize-indicator {
-  width: 100%;
-  height: 12px;
-  background-color: var(--icons);
-  margin-inline-start: var(--sidebar-resize-indicator-space);
-}
-
-[dir="rtl"] .sidebar .sidebar-resize-handle {
-  left: calc(var(--sidebar-resize-indicator-width) * -1);
-  right: unset;
-}
-.js .sidebar .sidebar-resize-handle {
-  cursor: col-resize;
-  width: calc(
-    var(--sidebar-resize-indicator-width) -
-      var(--sidebar-resize-indicator-space)
-  );
-}
-/* sidebar-hidden */
-#sidebar-toggle-anchor:not(:checked) ~ .sidebar {
-  transform: translateX(
-    calc(0px - var(--sidebar-width) - var(--sidebar-resize-indicator-width))
-  );
-  z-index: -1;
-}
-[dir="rtl"] #sidebar-toggle-anchor:not(:checked) ~ .sidebar {
-  transform: translateX(
-    calc(var(--sidebar-width) + var(--sidebar-resize-indicator-width))
-  );
-}
-.sidebar::-webkit-scrollbar {
-  background: var(--sidebar-bg);
-}
-.sidebar::-webkit-scrollbar-thumb {
-  background: var(--scrollbar);
-}
-
-/* sidebar-visible */
-#sidebar-toggle-anchor:checked ~ .page-wrapper {
-  transform: translateX(
-    calc(var(--sidebar-width) + var(--sidebar-resize-indicator-width))
-  );
-}
-[dir="rtl"] #sidebar-toggle-anchor:checked ~ .page-wrapper {
-  transform: translateX(
-    calc(0px - var(--sidebar-width) - var(--sidebar-resize-indicator-width))
-  );
-}
-@media only screen and (min-width: 620px) {
-  #sidebar-toggle-anchor:checked ~ .page-wrapper {
-    transform: none;
-    margin-inline-start: calc(
-      var(--sidebar-width) + var(--sidebar-resize-indicator-width)
-    );
-  }
-  [dir="rtl"] #sidebar-toggle-anchor:checked ~ .page-wrapper {
-    transform: none;
-  }
-}
-
-.chapter {
-  list-style: none outside none;
-  padding-inline-start: 0;
-  line-height: 2.2em;
-}
-
-.chapter ol {
-  width: 100%;
-}
-
-.chapter li {
-  display: flex;
-  color: var(--sidebar-non-existent);
-}
-.chapter li a {
-  display: block;
-  padding: 0;
-  text-decoration: none;
-  color: var(--sidebar-fg);
-}
-
-.chapter li a:hover {
-  color: var(--sidebar-active);
-}
-
-.chapter li a.active {
-  color: var(--sidebar-active);
-}
-
-.chapter li > a.toggle {
-  cursor: pointer;
-  display: block;
-  margin-inline-start: auto;
-  padding: 0 10px;
-  user-select: none;
-  opacity: 0.68;
-}
-
-.chapter li > a.toggle div {
-  transition: transform 0.5s;
-}
-
-/* collapse the section */
-.chapter li:not(.expanded) + li > ol {
-  display: none;
-}
-
-.chapter li.chapter-item {
-  line-height: 1.5em;
-  margin-block-start: 0.6em;
-}
-
-.chapter li.expanded > a.toggle div {
-  transform: rotate(90deg);
-}
-
-.spacer {
-  width: 100%;
-  height: 3px;
-  margin: 5px 0px;
-}
-.chapter .spacer {
-  background-color: var(--sidebar-spacer);
-}
-
-@media (-moz-touch-enabled: 1), (pointer: coarse) {
-  .chapter li a {
-    padding: 5px 0;
-  }
-  .spacer {
-    margin: 10px 0;
-  }
-}
-
-.section {
-  list-style: none outside none;
-  padding-inline-start: 20px;
-  line-height: 1.9em;
-}
-
-/* Theme Menu Popup */
-
-.theme-popup {
-  position: absolute;
-  left: 10px;
-  top: var(--menu-bar-height);
-  z-index: 1000;
-  border-radius: 4px;
-  font-size: 0.7em;
-  color: var(--fg);
-  background: var(--theme-popup-bg);
-  border: 1px solid var(--theme-popup-border);
-  margin: 0;
-  padding: 0;
-  list-style: none;
-  display: none;
-  /* Don't let the children's background extend past the rounded corners. */
-  overflow: hidden;
-}
-[dir="rtl"] .theme-popup {
-  left: unset;
-  right: 10px;
-}
-.theme-popup .default {
-  color: var(--icons);
-}
-.theme-popup .theme {
-  width: 100%;
-  border: 0;
-  margin: 0;
-  padding: 2px 20px;
-  line-height: 25px;
-  white-space: nowrap;
-  text-align: start;
-  cursor: pointer;
-  color: inherit;
-  background: inherit;
-  font-size: inherit;
-}
-.theme-popup .theme:hover {
-  background-color: var(--theme-hover);
-}
-
-.theme-selected::before {
-  display: inline-block;
-  content: "✓";
-  margin-inline-start: -14px;
-  width: 14px;
-}
diff --git a/theme/css/general.css b/theme/css/general.css
deleted file mode 100644
index 8d82f0043d06..000000000000
--- a/theme/css/general.css
+++ /dev/null
@@ -1,279 +0,0 @@
-/* Base styles and content styles */
-
-:root {
-  /* Browser default font-size is 16px, this way 1 rem = 10px */
-  font-size: 62.5%;
-  color-scheme: var(--color-scheme);
-}
-
-html {
-  font-family: "Open Sans", sans-serif;
-  color: var(--fg);
-  background-color: var(--bg);
-  text-size-adjust: none;
-  -webkit-text-size-adjust: none;
-}
-
-body {
-  margin: 0;
-  font-size: 1.6rem;
-  overflow-x: hidden;
-}
-
-code {
-  font-family: var(--mono-font) !important;
-  font-size: var(--code-font-size);
-  direction: ltr !important;
-}
-
-/* make long words/inline code not x overflow */
-main {
-  overflow-wrap: break-word;
-}
-
-/* make wide tables scroll if they overflow */
-.table-wrapper {
-  overflow-x: auto;
-}
-
-/* Don't change font size in headers. */
-h1 code,
-h2 code,
-h3 code,
-h4 code,
-h5 code,
-h6 code {
-  font-size: unset;
-}
-
-.left {
-  float: left;
-}
-.right {
-  float: right;
-}
-.boring {
-  opacity: 0.6;
-}
-.hide-boring .boring {
-  display: none;
-}
-.hidden {
-  display: none !important;
-}
-
-h2 {
-  margin-block-start: 2.5em;
-}
-h3,
-h4,
-h5 {
-  margin-block-start: 2em;
-}
-
-.header + .header h3,
-.header + .header h4,
-.header + .header h5 {
-  margin-block-start: 1em;
-}
-
-h1:target::before,
-h2:target::before,
-h3:target::before,
-h4:target::before,
-h5:target::before,
-h6:target::before {
-  display: inline-block;
-  content: "»";
-  margin-inline-start: -30px;
-  width: 30px;
-}
-
-/* This is broken on Safari as of version 14, but is fixed
-   in Safari Technology Preview 117 which I think will be Safari 14.2.
-   https://bugs.webkit.org/show_bug.cgi?id=218076
-*/
-:target {
-  /* Safari does not support logical properties */
-  scroll-margin-top: calc(var(--menu-bar-height) + 0.5em);
-}
-
-.page {
-  outline: 0;
-  padding: 0 var(--page-padding);
-  margin-block-start: calc(
-    0px - var(--menu-bar-height)
-  ); /* Compensate for the #menu-bar-hover-placeholder */
-}
-.page-wrapper {
-  box-sizing: border-box;
-  background-color: var(--bg);
-}
-.no-js .page-wrapper,
-.js:not(.sidebar-resizing) .page-wrapper {
-  transition: margin-left 0.3s ease, transform 0.3s ease; /* Animation: slide away */
-}
-[dir="rtl"] .js:not(.sidebar-resizing) .page-wrapper {
-  transition: margin-right 0.3s ease, transform 0.3s ease; /* Animation: slide away */
-}
-
-.content {
-  overflow-y: auto;
-  padding: 0 5px 50px 5px;
-}
-.content main {
-  margin-inline-start: auto;
-  margin-inline-end: auto;
-  max-width: var(--content-max-width);
-}
-.content p {
-  line-height: 1.45em;
-}
-.content ol {
-  line-height: 1.45em;
-}
-.content ul {
-  line-height: 1.45em;
-}
-.content a {
-  text-decoration: underline;
-}
-.content a:hover {
-  text-decoration: underline dotted;
-}
-.content img,
-.content video {
-  max-width: 100%;
-}
-.content .header:link,
-.content .header:visited {
-  color: var(--fg);
-}
-.content .header:link,
-.content .header:visited:hover {
-  text-decoration: none;
-}
-
-table {
-  margin: 0 auto;
-  border-collapse: collapse;
-}
-table td {
-  padding: 3px 20px;
-  border: 1px var(--table-border-color) solid;
-}
-table thead {
-  background: var(--table-header-bg);
-}
-table thead td {
-  font-weight: 700;
-  border: none;
-}
-table thead th {
-  padding: 3px 20px;
-}
-table thead tr {
-  border: 1px var(--table-header-bg) solid;
-}
-/* Alternate background colors for rows */
-table tbody tr:nth-child(2n) {
-  background: var(--table-alternate-bg);
-}
-
-blockquote {
-  margin: 20px 0;
-  padding: 0 20px;
-  color: var(--fg);
-  background-color: var(--quote-bg);
-  border-block-start: 0.1em solid var(--quote-border);
-  border-block-end: 0.1em solid var(--quote-border);
-}
-
-.warning {
-  margin: 20px;
-  padding: 0 20px;
-  border-inline-start: 2px solid var(--warning-border);
-}
-
-.warning:before {
-  position: absolute;
-  width: 3rem;
-  height: 3rem;
-  margin-inline-start: calc(-1.5rem - 21px);
-  content: "ⓘ";
-  text-align: center;
-  background-color: var(--bg);
-  color: var(--warning-border);
-  font-weight: bold;
-  font-size: 2rem;
-}
-
-blockquote .warning:before {
-  background-color: var(--quote-bg);
-}
-
-kbd {
-  background-color: var(--table-border-color);
-  border-radius: 4px;
-  border: solid 1px var(--theme-popup-border);
-  box-shadow: inset 0 -1px 0 var(--theme-hover);
-  display: inline-block;
-  font-size: var(--code-font-size);
-  font-family: var(--mono-font);
-  line-height: 10px;
-  padding: 4px 5px;
-  vertical-align: middle;
-}
-
-sup {
-  /* Set the line-height for superscript and footnote references so that there
-       isn't an awkward space appearing above lines that contain the footnote.
-
-       See https://github.com/rust-lang/mdBook/pull/2443#discussion_r1813773583
-       for an explanation.
-    */
-  line-height: 0;
-}
-
-:not(.footnote-definition) + .footnote-definition,
-.footnote-definition + :not(.footnote-definition) {
-  margin-block-start: 2em;
-}
-.footnote-definition {
-  font-size: 0.9em;
-  margin: 0.5em 0;
-}
-.footnote-definition p {
-  display: inline;
-}
-
-.tooltiptext {
-  position: absolute;
-  visibility: hidden;
-  color: #fff;
-  background-color: #333;
-  transform: translateX(
-    -50%
-  ); /* Center by moving tooltip 50% of its width left */
-  left: -8px; /* Half of the width of the icon */
-  top: -35px;
-  font-size: 0.8em;
-  text-align: center;
-  border-radius: 6px;
-  padding: 5px 8px;
-  margin: 5px;
-  z-index: 1000;
-}
-.tooltipped .tooltiptext {
-  visibility: visible;
-}
-
-.chapter li.part-title {
-  color: var(--sidebar-fg);
-  margin: 5px 0px;
-  font-weight: bold;
-}
-
-.result-no-output {
-  font-style: italic;
-}
diff --git a/theme/css/speaker-notes.css b/theme/css/speaker-notes.css
index a16e1bee3551..7c14a17fad3f 100644
--- a/theme/css/speaker-notes.css
+++ b/theme/css/speaker-notes.css
@@ -5,17 +5,16 @@
   padding: 0.25em;
 }
 
-.content details summary h3 {
+.content details summary h4 {
   display: inline-block;
   list-style: none;
   font-weight: normal;
   font-style: italic;
-  font-size: 1.6rem;
   margin: 0.5em 0.25em;
   cursor: pointer;
 }
 
-.content details summary h3:target::before {
+.content details summary h4:target::before {
   margin-left: -40px;
   width: 40px;
 }
diff --git a/theme/index.hbs b/theme/index.hbs
index 8be38847c76b..625d6443be66 100644
--- a/theme/index.hbs
+++ b/theme/index.hbs
@@ -289,6 +289,7 @@
 
                 <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
                 <script>
+                    document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
                     document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
                         link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
diff --git a/theme/speaker-notes.js b/theme/speaker-notes.js
index 537f6214100d..6247ea3ffa28 100644
--- a/theme/speaker-notes.js
+++ b/theme/speaker-notes.js
@@ -95,23 +95,21 @@
     let summary = document.createElement("summary");
     notes.insertBefore(summary, notes.firstChild);
 
-    let h3 = document.createElement("h3");
-    h3.setAttribute("id", "speaker-notes");
-    h3.append("Speaker Notes");
-    h3.addEventListener("click", (event) => {
+    let h4 = document.createElement("h4");
+    h4.setAttribute("id", "speaker-notes");
+    h4.append("Speaker Notes");
+    h4.addEventListener("click", (event) => {
       // Update fragment as if we had clicked a link. A regular a element would
       // result in double-fire of the event.
       window.location.hash = "#speaker-notes";
     });
-    summary.append(h3);
+    summary.append(h4);
 
     // Create pop-out button.
     let popOutLocation = new URL(window.location.href);
     popOutLocation.hash = "#speaker-notes-open";
     let popOut = document.createElement("button");
     popOut.classList.add("icon-button", "pop-out");
-    popOut.setAttribute("title", "Open speaker notes in a new window");
-    popOut.setAttribute("aria-label", "Open speaker notes in a new window");
     popOut.addEventListener("click", (event) => {
       let popup = window.open(popOutLocation.href, "speakerNotes", "popup");
       if (popup) {