diff --git a/_static/css/custom.css b/_static/css/custom.css
index f403badba..bcb8b3a50 100644
--- a/_static/css/custom.css
+++ b/_static/css/custom.css
@@ -30,6 +30,7 @@
     --content-wrap-background-color: #efefef;
     --content-background-color: #fcfcfc;
     --logo-opacity: 1.0;
+
     --navbar-background-color: #333f67;
     --navbar-background-color-hover: #29355c;
     --navbar-background-color-active: #212d51;
@@ -37,9 +38,14 @@
     --navbar-current-background-color-hover: #182343;
     --navbar-current-background-color-active: #131e3b;
     --navbar-category-active-color: rgba(255 115 129 / 10%);
+    --navbar-current-color: #f1f9ff;
     --navbar-level-1-color: #c3e3ff;
     --navbar-level-2-color: #b8d6f0;
     --navbar-level-3-color: #a3c4e1;
+    --navbar-expand-base-color: #81a3c2;
+    --navbar-expand-hover-color: #c3e3ff;
+    --navbar-expand-active-color: #f1f9ff;
+    --navbar-dimmed-color: #a3c4e1;
     --navbar-heading-color: #ff7381;
     --navbar-scrollbar-color: #d45a66;
     --navbar-scrollbar-hover-color: #b14550;
@@ -141,6 +147,7 @@
         --content-background-color: #2e3236;
         /* Decrease the logo opacity when using the dark theme to be less distracting */
         --logo-opacity: 0.85;
+
         --navbar-background-color: #25282b;
         --navbar-background-color-hover: #333639;
         --navbar-background-color-active: #111417;
@@ -148,9 +155,14 @@
         --navbar-current-background-color-hover: #44474a;
         --navbar-current-background-color-active: #222528;
         --navbar-category-active-color: rgba(238 115 129 / 10%);
+        --navbar-current-color: #fefefe;
         --navbar-level-1-color: #ddd;
         --navbar-level-2-color: #ccc;
         --navbar-level-3-color: #bbb;
+        --navbar-expand-base-color: #80848e;
+        --navbar-expand-hover-color: #ccc;
+        --navbar-expand-active-color: #ddd;
+        --navbar-dimmed-color: #bbb;
         --navbar-heading-color: #ee7381;
         --navbar-scrollbar-color: #be5460;
         --navbar-scrollbar-hover-color: #963e48;
@@ -1215,6 +1227,8 @@ p + .classref-constant {
 
 .wy-side-nav-search {
     background-color: var(--navbar-background-color);
+    color: var(--navbar-level-1-color);
+    margin-right: 8px;
 }
 
 .wy-side-nav-search.fixed {
@@ -1266,7 +1280,22 @@ p + .classref-constant {
     opacity: 0.55;
 }
 
-/* Navigation bar */
+/* Version branch label below the logo */
+.wy-side-nav-search > div.version {
+    color: var(--navbar-dimmed-color);
+    font-size: 14px;
+    opacity: 0.9;
+}
+
+/* Navigational top bar (mobile only) */
+
+.wy-nav-top,
+.wy-nav-top a {
+    background-color: var(--navbar-background-color);
+    color: var(--navbar-level-1-color);
+}
+
+/* Navigational sidebar */
 
 .wy-nav-side {
     background-color: var(--navbar-background-color);
@@ -1287,119 +1316,134 @@ p + .classref-constant {
     letter-spacing: 0.75px;
 }
 
-/* Mobile navigation */
+/* Default styling of navigation items */
 
-.wy-nav-top,
-.wy-nav-top a {
+.wy-menu-vertical li {
     background-color: var(--navbar-background-color);
+}
+.wy-menu-vertical li.current {
+    background-color: var(--navbar-current-background-color);
+}
+
+.wy-menu-vertical li > a {
     color: var(--navbar-level-1-color);
+    font-size: 92%;
+    line-height: 20px;
+    padding: .4045em 1.618em;
 }
-
-/* Version branch label below the logo */
-.wy-side-nav-search > div.version {
-    color: var(--navbar-level-3-color);
-    font-size: 14px;
-    opacity: 0.9;
-}
-
-/* First level of navigation items */
-
-.wy-menu-vertical a {
-    color: var(--navbar-level-1-color);
-}
-
-.wy-menu-vertical a:hover {
+.wy-menu-vertical li > a:hover {
     background-color: var(--navbar-background-color-hover);
     color: var(--navbar-level-1-color);
 }
-
-.wy-menu-vertical a:active {
+.wy-menu-vertical li > a:active {
     background-color: var(--navbar-background-color-active);
 }
 
-.wy-menu-vertical li.toctree-l1 > a {
-    padding: .4045em 1.918em;
-}
-
-.wy-menu-vertical li.toctree-l1.current > a {
-    border: none;
-}
-
-.wy-side-nav-search, .wy-menu-vertical a, .wy-menu-vertical a button.toctree-expand,
-.wy-menu-vertical li.toctree-l1 a button.toctree-expand,
-.wy-menu-vertical li.toctree-l2 a button.toctree-expand {
-    color: var(--navbar-level-3-color);
+.wy-menu-vertical li > a button.toctree-expand {
+    color: var(--navbar-expand-base-color) !important;
     opacity: 0.9;
     margin-right: 8px;
-}
 
-.wy-side-nav-search, .wy-menu-vertical a, .wy-menu-vertical a:hover button.toctree-expand,
-.wy-menu-vertical li.toctree-l1 a:hover button.toctree-expand,
-.wy-menu-vertical li.toctree-l2 a:hover button.toctree-expand {
-    color: var(--navbar-level-2-color);
-    opacity: 1;
-}
-
-.wy-side-nav-search, .wy-menu-vertical a, .wy-menu-vertical a:active button.toctree-expand,
-.wy-menu-vertical li.toctree-l1 a:active button.toctree-expand,
-.wy-menu-vertical li.toctree-l2 a:active button.toctree-expand {
-    color: var(--navbar-level-1-color);
-    opacity: 1;
-}
-
-/* Second (and higher) levels of navigation items */
-
-.wy-menu-vertical li.current a {
-    /* Make long words always display on a single line, keep wrapping for multiple words */
-    /* This fixes the class reference titles' display with very long class names */
-    display: flex;
-}
-
-.wy-menu-vertical li.current a,
-.wy-menu-vertical li.toctree-l2.current > a,
-.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a,
-.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a {
-    background-color: var(--navbar-current-background-color);
-    color: var(--navbar-level-2-color);
-    border-color: var(--navbar-current-background-color);
-}
-
-.wy-menu-vertical li.current a:hover,
-.wy-menu-vertical li.toctree-l2.current > a:hover,
-.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a:hover,
-.wy-menu-vertical li.toctree-l3.current li.toctree-l4 > a:hover {
-    background-color: var(--navbar-current-background-color-hover);
-}
-
-.wy-menu-vertical li.current a:active,
-.wy-menu-vertical li.toctree-l2.current > a:active,
-.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a:active,
-.wy-menu-vertical li.toctree-l3.current li.toctree-l4 > a:active {
-    background-color: var(--navbar-current-background-color-active);
-}
-
-.wy-menu-vertical a {
-    /* This overrides 8px margin added in other multi-selector rules */
-    margin-right: 0;
-}
-
-/* Make the expand icon a bit easier to hit. */
-.wy-menu-vertical li a button.toctree-expand {
+    /* Make the expand icon a bit easier to hit. */
     position: relative;
     width: 12px;
     min-width: 12px; /* Forces the size to stay this way in the flexbox model. */
     height: 18px;
 }
+.wy-menu-vertical li.current > a button.toctree-expand {
+    color: var(--navbar-current-color) !important;
+}
+.wy-menu-vertical li > a:hover button.toctree-expand {
+    color: var(--navbar-expand-hover-color) !important;
+    opacity: 1;
+}
+.wy-menu-vertical li > a:active button.toctree-expand {
+    color: var(--navbar-expand-active-color) !important;
+    opacity: 1;
+}
 
-.wy-menu-vertical li a button.toctree-expand:before {
+/* Make the expand icon a bit easier to hit. */
+.wy-menu-vertical li > a button.toctree-expand:before {
     position: absolute;
-    top: -3px;
+    top: -2px;
     left: -6px;
     width: 24px;
     height: 24px;
     padding: 6px;
 }
 
+.wy-menu-vertical li.current > a,
+.wy-menu-vertical li.toctree-l2.current > a {
+    background-color: var(--navbar-current-background-color-hover);
+    border-bottom: 2px solid var(--navbar-current-background-color);
+    color: var(--navbar-current-color);
+    font-weight: 600;
+
+    /* Make long words always display on a single line, keep wrapping for multiple words */
+    /* This fixes the class reference titles' display with very long class names */
+    display: flex;
+}
+.wy-menu-vertical li.current > a:hover,
+.wy-menu-vertical li.toctree-l2.current > a:hover {
+    background-color: var(--navbar-current-background-color-hover);
+}
+.wy-menu-vertical li.current > a:active,
+.wy-menu-vertical li.toctree-l2.current > a:active {
+    background-color: var(--navbar-current-background-color-active);
+}
+
+/* Slightly adjust first level items. */
+.wy-menu-vertical li.toctree-l1 > a,
+.wy-menu-vertical li.toctree-l1.current > a {
+    border: none;
+    padding: .4045em 1.918em;
+}
+.wy-menu-vertical li.toctree-l1.current > a {
+    border-bottom: 2px solid var(--navbar-current-background-color);
+}
+
+/* Override styling for children of the current item. */
+.wy-menu-vertical li.current li > a,
+.wy-menu-vertical li.toctree-l2.current li > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a {
+    background-color: var(--navbar-current-background-color);
+    border: none;
+    border-bottom: 2px solid var(--navbar-current-background-color);
+    color: var(--navbar-level-2-color);
+}
+.wy-menu-vertical li.current li > a:hover,
+.wy-menu-vertical li.toctree-l2.current li > a:hover,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a:hover,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a:hover {
+    background-color: var(--navbar-current-background-color-hover);
+}
+.wy-menu-vertical li.current li > a:active,
+.wy-menu-vertical li.toctree-l2.current li > a:active,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a:active,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a:active {
+    background-color: var(--navbar-current-background-color-active);
+}
+
+.wy-menu-vertical li.toctree-l2.current li > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a {
+    color: var(--navbar-level-3-color);
+}
+.wy-menu-vertical li.toctree-l2.current li > a:hover,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3 > a:hover,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4 > a:hover {
+    color: var(--navbar-level-1-color);
+}
+
+.wy-menu-vertical li.current li.current > a,
+.wy-menu-vertical li.toctree-l2.current li.current > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l3.current > a,
+.wy-menu-vertical li.toctree-l2.current li.toctree-l4.current > a {
+    color: var(--navbar-current-color);
+    font-weight: 600;
+}
+
 /* Banner panel in sidebar */
 .wy-nav-side .ethical-rtd.fixed {
     position: fixed;
@@ -1459,7 +1503,7 @@ p + .classref-constant {
 }
 
 .rst-versions .rst-other-versions small {
-    color: var(--navbar-level-3-color);
+    color: var(--navbar-dimmed-color);
 }
 
 .rst-versions .rst-other-versions dd a:hover {
diff --git a/_static/js/custom.js b/_static/js/custom.js
index ac0d267a1..899bc76c0 100644
--- a/_static/js/custom.js
+++ b/_static/js/custom.js
@@ -200,10 +200,21 @@ const registerSidebarObserver = (function(){
     // theme adds an extra button to fold and unfold the tree without navigating away.
     // But that means that the buttons are added after the initial load, so we need to
     // improvise to detect clicks on these buttons.
+    const scrollElement = document.querySelector('.wy-menu-vertical');
     const registerLinkHandler = (linkChildren) => {
       linkChildren.forEach(it => {
         if (it.nodeType === Node.ELEMENT_NODE && it.classList.contains('toctree-expand')) {
           it.addEventListener('click', () => {
+            // Toggling a different item will close the currently opened one,
+            // which may shift the clicked item out of the view. We correct for that.
+            const menuItem = it.parentNode;
+            const baseScrollOffset = scrollElement.scrollTop + scrollElement.offsetTop;
+            const maxScrollOffset = baseScrollOffset + scrollElement.offsetHeight;
+
+            if (menuItem.offsetTop < baseScrollOffset || menuItem.offsetTop > maxScrollOffset) {
+              menuItem.scrollIntoView();
+            }
+
             callback();
           });
         }
@@ -212,7 +223,7 @@ const registerSidebarObserver = (function(){
 
     const navigationSections = document.querySelectorAll('.wy-menu-vertical ul');
     navigationSections.forEach(it => {
-      if (typeof it.previousSibling === 'undefined' || it.previousSibling.tagName != 'A') {
+      if (it.previousSibling == null || typeof it.previousSibling === 'undefined' || it.previousSibling.tagName != 'A') {
         return;
       }
 
diff --git a/conf.py b/conf.py
index b08226da8..6430a4e51 100644
--- a/conf.py
+++ b/conf.py
@@ -189,14 +189,14 @@ html_extra_path = ["robots.txt"]
 html_css_files = [
     'css/algolia.css',
     'https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.css',
-    "css/custom.css?5", # Increment the number at the end when the file changes to bust the cache.
+    "css/custom.css?6", # Increment the number at the end when the file changes to bust the cache.
 ]
 
 if not on_rtd:
     html_css_files.append("css/dev.css")
 
 html_js_files = [
-    "js/custom.js?3", # Increment the number at the end when the file changes to bust the cache.
+    "js/custom.js?4", # Increment the number at the end when the file changes to bust the cache.
     ('https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.js', {'defer': 'defer'}),
     ('js/algolia.js', {'defer': 'defer'})
 ]