diff --git a/_includes/head.html b/_includes/head.html
index 0fc40f5..45944de 100644
--- a/_includes/head.html
+++ b/_includes/head.html
@@ -10,13 +10,10 @@
     (function () {
       try {
         var stored = localStorage.getItem('theme');
-        var theme = (stored === 'light' || stored === 'dark' || stored === 'system') ? stored : 'system';
-        if (theme === 'system') {
-          if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
-            document.documentElement.setAttribute('data-theme', 'dark');
-          }
-        } else {
-          document.documentElement.setAttribute('data-theme', theme);
+        if (stored === 'light' || stored === 'dark') {
+          document.documentElement.setAttribute('data-theme', stored);
+        } else if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
+          document.documentElement.setAttribute('data-theme', 'dark');
         }
       } catch (e) {}
     })();
diff --git a/_includes/nav.html b/_includes/nav.html
index b834bd9..e3ee839 100644
--- a/_includes/nav.html
+++ b/_includes/nav.html
@@ -41,7 +41,7 @@
           <a href="{{ site.feed.path }}" class="navbar-item"><img src="{{ site.baseurl }}/assets/images/rss.png"/></a>
           <a class="navbar-item theme-toggle" role="button" aria-label="Toggle theme" title="Toggle theme">
             <span class="icon">
-              <i class="fa fa-desktop" aria-hidden="true"></i>
+              <i class="fa fa-moon-o" aria-hidden="true"></i>
             </span>
           </a>
         </div>
diff --git a/_layouts/aggregate_default.html b/_layouts/aggregate_default.html
index 05ff48f..7146dd0 100644
--- a/_layouts/aggregate_default.html
+++ b/_layouts/aggregate_default.html
@@ -58,7 +58,7 @@
               <a href="{{ site.feed.path }}" class="navbar-item"><img src="{{ site.baseurl }}/assets/images/rss.png"/></a>
               <a class="navbar-item theme-toggle" role="button" aria-label="Toggle theme" title="Toggle theme">
                 <span class="icon">
-                  <i class="fa fa-desktop" aria-hidden="true"></i>
+                  <i class="fa fa-moon-o" aria-hidden="true"></i>
                 </span>
               </a>
             </div>
diff --git a/_layouts/author_default.html b/_layouts/author_default.html
index 8b9f1e2..0f2ccb0 100644
--- a/_layouts/author_default.html
+++ b/_layouts/author_default.html
@@ -68,7 +68,7 @@
               <a href="{{ site.feed.path }}" class="navbar-item"><img src="{{ site.baseurl }}/assets/images/rss.png"/></a>
               <a class="navbar-item theme-toggle" role="button" aria-label="Toggle theme" title="Toggle theme">
                 <span class="icon">
-                  <i class="fa fa-desktop" aria-hidden="true"></i>
+                  <i class="fa fa-moon-o" aria-hidden="true"></i>
                 </span>
               </a>
             </div>
diff --git a/assets/js/theme.js b/assets/js/theme.js
index 9351193..4f8ccad 100644
--- a/assets/js/theme.js
+++ b/assets/js/theme.js
@@ -3,50 +3,48 @@ layout: null
 ---
 (function () {
     var STORAGE_KEY = "theme";
-    var THEMES = ["light", "dark", "system"];
     var ICONS = {
         light: "fa-sun-o",
-        dark: "fa-moon-o",
-        system: "fa-desktop"
+        dark: "fa-moon-o"
     };
 
     function getStoredTheme() {
         try {
             var stored = localStorage.getItem(STORAGE_KEY);
-            return THEMES.indexOf(stored) >= 0 ? stored : "system";
+            return (stored === "light" || stored === "dark") ? stored : null;
         } catch (e) {
-            return "system";
+            return null;
         }
     }
 
-    function applyTheme(theme) {
-        if (theme === "system") {
-            var prefersDark = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches;
-            if (prefersDark) {
-                document.documentElement.setAttribute("data-theme", "dark");
-            } else {
-                document.documentElement.removeAttribute("data-theme");
-            }
-        } else {
-            document.documentElement.setAttribute("data-theme", theme);
+    function getCurrentTheme() {
+        var stored = getStoredTheme();
+        if (stored) {
+            return stored;
         }
+        var prefersDark = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches;
+        return prefersDark ? "dark" : "light";
+    }
+
+    function applyTheme(theme) {
+        document.documentElement.setAttribute("data-theme", theme);
     }
 
     function updateButtons(theme) {
+        var nextLabel = theme === "dark" ? "Switch to light theme" : "Switch to dark theme";
         var buttons = document.querySelectorAll(".theme-toggle");
         for (var i = 0; i < buttons.length; i++) {
             var icon = buttons[i].querySelector(".fa");
             if (icon) {
                 icon.className = "fa " + ICONS[theme];
             }
-            buttons[i].setAttribute("aria-label", "Theme: " + theme + " (click to change)");
-            buttons[i].setAttribute("title", "Theme: " + theme + " (click to change)");
+            buttons[i].setAttribute("aria-label", nextLabel);
+            buttons[i].setAttribute("title", nextLabel);
         }
     }
 
-    function cycleTheme() {
-        var current = getStoredTheme();
-        var next = THEMES[(THEMES.indexOf(current) + 1) % THEMES.length];
+    function toggleTheme() {
+        var next = getCurrentTheme() === "dark" ? "light" : "dark";
         try {
             localStorage.setItem(STORAGE_KEY, next);
         } catch (e) {}
@@ -55,22 +53,23 @@ layout: null
     }
 
     function init() {
-        var current = getStoredTheme();
-        updateButtons(current);
+        updateButtons(getCurrentTheme());
 
         var buttons = document.querySelectorAll(".theme-toggle");
         for (var i = 0; i < buttons.length; i++) {
             buttons[i].addEventListener("click", function (e) {
                 e.preventDefault();
-                cycleTheme();
+                toggleTheme();
             });
         }
 
         if (window.matchMedia) {
             var mql = window.matchMedia("(prefers-color-scheme: dark)");
             var onChange = function () {
-                if (getStoredTheme() === "system") {
-                    applyTheme("system");
+                if (getStoredTheme() === null) {
+                    var sys = mql.matches ? "dark" : "light";
+                    applyTheme(sys);
+                    updateButtons(sys);
                 }
             };
             if (mql.addEventListener) {