added support for dark theme

app.py

@@ -59,6 +59,24 @@ COUNTER = """
             border-radius: 20px;
             z-index: 1;
         }
+        /* Dark theme adjustments */
+        @media (prefers-color-scheme: dark) {
+            .countdown-container::before {
+                background: rgba(0, 0, 0, 0.6);
+            }
+            
+            .title {
+                color: #ffffff;
+            }
+            
+            .number {
+                color: #ffffff;
+            }
+            
+            .label {
+                color: #cccccc;
+            }
+        }
         .countdown-container > * {
             position: relative;
             z-index: 2;