diff --git a/static/script.js b/static/script.js
index 459f784..ccb0115 100644
--- a/static/script.js
+++ b/static/script.js
@@ -68,7 +68,7 @@ function updateDots() {
     var dots = document.querySelectorAll("#dots .dot");
     dots.forEach(function(dot, index) {
         // index starts at 0 so add FIRST_IMG_ID to match your slide IDs
-        dot.className = "dot" + ((index + FIRST_IMG_ID) === current ? " active" : "");
+        dot.classList.toggle("active", (index + FIRST_IMG_ID) === current);
     });
 }
 
diff --git a/static/style.scss b/static/style.scss
index a5ccac0..8ab257f 100644
--- a/static/style.scss
+++ b/static/style.scss
@@ -376,7 +376,7 @@ iframe {
     margin: 0 0.25em;
     cursor: pointer;
 
-    .active {
+    &.active {
         background: #333;
     }
 }