Recolor UI with HTML theme-color meta tag

data/gresource.xml

@@ -1,9 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <gresources>
   <gresource prefix="/com/github/cassidyjames/ephemeral">
-    <file alias="styles/global.css">styles/global.css</file>
-    <file alias="styles/hera.css">styles/hera.css</file>
-    <file alias="styles/odin.css">styles/odin.css</file>
-    <file alias="styles/non-native.css">styles/non-native.css</file>
+    <file alias="styles/App.css">styles/App.css</file>
   </gresource>
 </gresources>

data/styles/global.css → data/styles/App.css

@@ -1,5 +1,5 @@
 /*
-* Copyright © 2019–2020 Cassidy James Blaede (https://cassidyjames.com)
+* Copyright © 2019–2021 Cassidy James Blaede (https://cassidyjames.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
@@ -24,6 +24,60 @@
 
 @define-color textColorPrimary alpha(white, 0.9);
 
+.titlebar,
+.titlebar button {
+    transition:
+      200ms ease background,
+      200ms ease color;
+}
+
+.titlebar button {
+  -gtk-icon-style: symbolic;
+  color: @html_meta_theme_color_fg;
+}
+
+.titlebar .image-button,
+.titlebar .titlebutton {
+  background: transparent;
+  color: @html_meta_theme_color_fg;
+  text-shadow: none;
+  -gtk-icon-shadow: none;
+}
+
+.titlebar .image-button.raised,
+.titlebar .linked .image-button {
+  background: rgba(255, 255, 255, 0.125);
+}
+
+.titlebar entry,
+.titlebar entry image {
+  color: @html_meta_theme_color_fg;
+}
+
+.titlebar entry {
+  background-color: mix(@html_meta_theme_color_bg, @html_meta_theme_color_fg, 0.125);
+}
+
+.titlebar .image-button:disabled {
+    opacity: 0.5;
+}
+
+.titlebar .linked .image-button:first-child {
+  border-top-left-radius: 9999px;
+  border-bottom-left-radius: 9999px;
+  padding-left: 0.5rem;
+}
+
+.titlebar .linked .image-button:last-child {
+  border-top-right-radius: 9999px;
+  border-bottom-right-radius: 9999px;
+  padding-right: 0.25rem;
+}
+
+.titlebar .linked.navigation .image-button:last-child {
+  padding-right: 0.5rem;
+}
+
 .browser-button .raised:last-child {
   padding: 0;
 }