diff --git a/assets/js/theme.js b/assets/js/theme.js
index 772d3ce..57da0d2 100644
--- a/assets/js/theme.js
+++ b/assets/js/theme.js
@@ -1,20 +1,26 @@
 (() => {
 	const root = document.documentElement;
+	const colorModes = ['auto', 'light', 'dark'];
 	const storedTheme = localStorage.getItem('c1024-theme');
-	if (storedTheme) root.dataset.theme = storedTheme;
+	let colorMode = colorModes.includes(storedTheme) ? storedTheme : 'auto';
+	root.dataset.theme = colorMode;
 
 	const themeToggle = document.querySelector('[data-theme-toggle]');
 	if (themeToggle) {
-		const updateThemeLabel = () => {
-			const dark = root.dataset.theme === 'dark';
-			themeToggle.setAttribute('aria-pressed', String(dark));
-			themeToggle.setAttribute('aria-label', dark ? 'Use light mode' : 'Use dark mode');
+		const themeIcon = themeToggle.querySelector('[data-theme-icon]');
+		const labels = { auto: 'Automatic', light: 'Light', dark: 'Dark' };
+		const icons = { auto: '#icon-auto', light: '#icon-light', dark: '#icon-dark' };
+		const updateThemeControl = () => {
+			const nextMode = colorModes[(colorModes.indexOf(colorMode) + 1) % colorModes.length];
+			themeToggle.setAttribute('aria-label', `Color mode: ${labels[colorMode]}. Activate to use ${labels[nextMode]} mode.`);
+			themeIcon.setAttribute('href', icons[colorMode]);
 		};
-		updateThemeLabel();
+		updateThemeControl();
 		themeToggle.addEventListener('click', () => {
-			root.dataset.theme = root.dataset.theme === 'dark' ? 'light' : 'dark';
-			localStorage.setItem('c1024-theme', root.dataset.theme);
-			updateThemeLabel();
+			colorMode = colorModes[(colorModes.indexOf(colorMode) + 1) % colorModes.length];
+			root.dataset.theme = colorMode;
+			localStorage.setItem('c1024-theme', colorMode);
+			updateThemeControl();
 		});
 	}
 
diff --git a/header.php b/header.php
index 9b32135..2106ee5 100644
--- a/header.php
+++ b/header.php
@@ -22,9 +22,9 @@
 		</nav>
 		<div class="header-actions">
 			<button class="icon-button" type="button" data-search-toggle aria-expanded="false" aria-controls="site-search"><span class="screen-reader-text"><?php esc_html_e( 'Open search', 'c1024-2026' ); ?></span><svg class="icon" aria-hidden="true"><use href="#icon-search"></use></svg></button>
-			<button class="icon-button" type="button" data-theme-toggle aria-pressed="false"><span class="screen-reader-text"><?php esc_html_e( 'Change color mode', 'c1024-2026' ); ?></span><svg class="icon" aria-hidden="true"><use href="#icon-theme"></use></svg></button>
+			<button class="icon-button" type="button" data-theme-toggle><span class="screen-reader-text"><?php esc_html_e( 'Change color mode', 'c1024-2026' ); ?></span><svg class="icon" aria-hidden="true"><use data-theme-icon href="#icon-auto"></use></svg></button>
 		</div>
 	</div>
 	<div class="search-panel" id="site-search" data-search-panel><?php get_search_form(); ?></div>
 </header>
-<svg width="0" height="0" class="screen-reader-text" aria-hidden="true"><symbol id="icon-search" viewBox="0 0 24 24"><circle cx="10.8" cy="10.8" r="6.5"></circle><path d="m16 16 5 5"></path></symbol><symbol id="icon-theme" viewBox="0 0 24 24"><circle cx="12" cy="12" r="4"></circle><path d="M12 2v2m0 16v2M2 12h2m16 0h2M4.9 4.9l1.4 1.4m11.4 11.4 1.4 1.4m0-14.2-1.4 1.4M6.3 17.7l-1.4 1.4"></path></symbol><symbol id="icon-menu" viewBox="0 0 24 24"><path d="M3 6h18M3 12h18M3 18h18"></path></symbol></svg>
+<svg width="0" height="0" class="screen-reader-text" aria-hidden="true"><symbol id="icon-search" viewBox="0 0 24 24"><circle cx="10.8" cy="10.8" r="6.5"></circle><path d="m16 16 5 5"></path></symbol><symbol id="icon-light" viewBox="0 0 24 24"><circle cx="12" cy="12" r="4"></circle><path d="M12 2v2m0 16v2M2 12h2m16 0h2M4.9 4.9l1.4 1.4m11.4 11.4 1.4 1.4m0-14.2-1.4 1.4M6.3 17.7l-1.4 1.4"></path></symbol><symbol id="icon-dark" viewBox="0 0 24 24"><path d="M20 15.2A8.5 8.5 0 0 1 8.8 4 8.5 8.5 0 1 0 20 15.2Z"></path></symbol><symbol id="icon-auto" viewBox="0 0 24 24"><circle cx="12" cy="12" r="7"></circle><path d="M12 2v2m0 16v2M2 12h2m16 0h2M5 5l1.4 1.4m11.2 11.2L19 19m0-14-1.4 1.4M6.4 17.6 5 19M9.5 15l2.5-6 2.5 6m-4-2h3"></path></symbol><symbol id="icon-menu" viewBox="0 0 24 24"><path d="M3 6h18M3 12h18M3 18h18"></path></symbol></svg>
diff --git a/style.css b/style.css
index 4aa4e90..5419ada 100644
--- a/style.css
+++ b/style.css
@@ -73,6 +73,22 @@ License URI: https://www.gnu.org/licenses/gpl-2.0.html
   --code-text: #f5eee5;
   --shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
 }
+@media (prefers-color-scheme: dark) {
+  :root:not([data-theme]),
+  :root[data-theme="auto"] {
+    color-scheme: dark;
+    --bg: #171615;
+    --surface: #22201e;
+    --text: #eee8e1;
+    --muted: #b9afa5;
+    --line: #4a4540;
+    --accent: #f07a3c;
+    --accent-hover: #ff9d6a;
+    --code-bg: #0e0e0d;
+    --code-text: #f5eee5;
+    --shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
+  }
+}
 * {
   box-sizing: border-box;
 }
@@ -183,7 +199,7 @@ button {
   margin: 0.1rem 0 0;
   color: var(--muted);
   font-family: "Berkeley Mono", monospace;
-  font-size: 0.64rem;
+  font-size: 1rem;
   letter-spacing: 0.07em;
 }
 .primary-menu {
@@ -194,7 +210,7 @@ button {
   padding: 0;
   list-style: none;
   font-family: "Berkeley Mono", monospace;
-  font-size: 0.7rem;
+  font-size: 1rem;
   letter-spacing: 0.04em;
 }
 .primary-menu a {
@@ -742,6 +758,14 @@ h4 {
 .primary-menu > li.menu-item-has-children > a::after {
   vertical-align: -0.2em;
 }
+body.admin-bar .site-header {
+  top: 32px;
+}
+@media (max-width: 782px) {
+  body.admin-bar .site-header {
+    top: 46px;
+  }
+}
 @media (prefers-reduced-motion: reduce) {
   *,
   *::before,