diff --git a/book/text/theme/index.hbs b/book/text/theme/index.hbs
index 2853be47..e131c461 100644
--- a/book/text/theme/index.hbs
+++ b/book/text/theme/index.hbs
@@ -1,11 +1,11 @@
 <!DOCTYPE HTML>
-<html lang="{{ language }}" class="sidebar-visible no-js {{ default_theme }}">
+<html lang="{{ language }}" class="{{ default_theme }} sidebar-visible" dir="{{ text_direction }}">
     <head>
         <!-- Book generated using mdBook -->
         <meta charset="UTF-8">
         <title>{{ title }}</title>
         {{#if is_print }}
-        <meta name="robots" content="noindex" />
+        <meta name="robots" content="noindex">
         {{/if}}
         {{#if base_url}}
         <base href="{{ base_url }}">
@@ -17,7 +17,7 @@
 
         <meta name="description" content="{{ description }}">
         <meta name="viewport" content="width=device-width, initial-scale=1">
-        <meta name="theme-color" content="#ffffff" />
+        <meta name="theme-color" content="#ffffff">
 
         {{#if favicon_svg}}
         <link rel="icon" href="{{ path_to_root }}favicon.svg">
@@ -52,15 +52,17 @@
         <!-- MathJax -->
         <script async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
         {{/if}}
-    </head>
-    <body>
-    <div id="body-container">
+
         <!-- Provide site root to javascript -->
         <script>
             var path_to_root = "{{ path_to_root }}";
             var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "{{ preferred_dark_theme }}" : "{{ default_theme }}";
         </script>
-
+        <!-- Start loading toc.js asap -->
+        <script src="{{ path_to_root }}toc.js"></script>
+    </head>
+    <body>
+    <div id="body-container">
         <!-- Work around some values being stored in localStorage wrapped in quotes -->
         <script>
             try {
@@ -82,56 +84,40 @@
             var theme;
             try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
             if (theme === null || theme === undefined) { theme = default_theme; }
-            var html = document.querySelector('html');
-            html.classList.remove('no-js')
+            const html = document.documentElement;
             html.classList.remove('{{ default_theme }}')
             html.classList.add(theme);
-            html.classList.add('js');
+            html.classList.add("js");
         </script>
 
+        <input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
+
         <!-- Hide / unhide sidebar before it is displayed -->
         <script>
-            var html = document.querySelector('html');
             var sidebar = null;
+            var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
             if (document.body.clientWidth >= 1080) {
                 try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
                 sidebar = sidebar || 'visible';
             } else {
                 sidebar = 'hidden';
             }
+            sidebar_toggle.checked = sidebar === 'visible';
             html.classList.remove('sidebar-visible');
             html.classList.add("sidebar-" + sidebar);
         </script>
 
         <nav id="sidebar" class="sidebar" aria-label="Table of contents">
-            <div class="sidebar-scrollbox">
-                {{#toc}}{{/toc}}
+            <!-- populated by js -->
+            <mdbook-sidebar-scrollbox class="sidebar-scrollbox"></mdbook-sidebar-scrollbox>
+            <noscript>
+                <iframe class="sidebar-iframe-outer" src="{{ path_to_root }}toc.html"></iframe>
+            </noscript>
+            <div id="sidebar-resize-handle" class="sidebar-resize-handle">
+                <div class="sidebar-resize-indicator"></div>
             </div>
-            <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
         </nav>
 
-        <!-- Track and set sidebar scroll position -->
-        <script>
-            var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
-            sidebarScrollbox.addEventListener('click', function(e) {
-                if (e.target.tagName === 'A') {
-                    sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
-                }
-            }, { passive: true });
-            var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
-            sessionStorage.removeItem('sidebar-scroll');
-            if (sidebarScrollTop) {
-                // preserve sidebar scroll position when navigating via links within sidebar
-                sidebarScrollbox.scrollTop = sidebarScrollTop;
-            } else {
-                // scroll sidebar to current active section when navigating via "next/previous chapter" buttons
-                var activeSection = document.querySelector('#sidebar .active');
-                if (activeSection) {
-                    activeSection.scrollIntoView({ block: 'center' });
-                }
-            }
-        </script>
-
         <div id="page-wrapper" class="page-wrapper">
 
             <div class="page">
@@ -139,9 +125,9 @@
                 <div id="menu-bar-hover-placeholder"></div>
                 <div id="menu-bar" class="menu-bar sticky">
                     <div class="left-buttons">
-                        <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                        <label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
                             <i class="fa fa-bars"></i>
-                        </button>
+                        </label>
                         <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
                             <i class="fa fa-paint-brush"></i>
                         </button>
@@ -217,7 +203,7 @@
                         {{/previous}}
 
                         {{#next}}
-                            <a rel="next" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                            <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                                 <i class="fa fa-angle-right"></i>
                             </a>
                         {{/next}}
@@ -235,7 +221,7 @@
                 {{/previous}}
 
                 {{#next}}
-                    <a rel="next" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                    <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                         <i class="fa fa-angle-right"></i>
                     </a>
                 {{/next}}
@@ -327,9 +313,9 @@
         </script>
         {{else}}
         <script>
-        window.addEventListener('load', function() {
-            window.setTimeout(window.print, 100);
-        });
+         window.addEventListener('load', function() {
+             window.setTimeout(window.print, 100);
+         });
         </script>
         {{/if}}
         {{/if}}
