Add a "prefers-color-scheme" block

quiz.css

@@ -6,7 +6,7 @@
  * this work.  If not, see
  * http://creativecommons.org/publicdomain/zero/1.0/. */
 
-/* $Id: quiz.css,v 1.3 2024/01/21 13:01:04 oj14ozun Exp oj14ozun $ */
+/* $Id: quiz.css,v 1.4 2024/01/22 10:08:19 oj14ozun Exp oj14ozun $ */
 
 :root {
     font-family: system-ui, "Open Sans", "Noto Sans", "Lato", Arial, sans-serif;
@@ -274,3 +274,23 @@ footer > code {
 	opacity: 50%;
     }
 }
+
+/* basic "dark theme" support */
+@media screen and (prefers-color-scheme: dark) {
+    :root {
+	--deafult-tint: darkslategray;
+	--highlight: cyan;
+	--correct: seagreen;
+	--wrong: maroon;
+	--ambiguous: sienna;
+    }
+
+    html {
+	background: black;
+	color: white;
+    }
+
+    a, button, input {
+	filter: invert(90%);
+    }
+}