@@ -21,6 +21,21 @@ <h2>Update CSS Variables with <span class='hl'>JS</span></h2>
   <img src="https://source.unsplash.com/7bwQXzbF6KE/800x500">
 
   <style>
+    :root {
+      --blur: 10px;
+      --spacing: 20px;
+      --base: #ffc600;
+    }
+
+    img {
+      padding: var(--spacing);
+      background: var(--base);
+      filter: blur(var(--blur));
+    }
+
+    .hl {
+      color: var(--base);
+    }
 
     /*
       misc styles, nothing to do with CSS variables
@@ -53,6 +68,16 @@ <h2>Update CSS Variables with <span class='hl'>JS</span></h2>
   </style>
 
   <script>
+  const inputs = document.querySelectorAll('.controls input');
+  const styleSheet = document.documentElement.style;
+
+  function handleUpdate () {
+    const suffix = this.dataset.sizing || '';
+    styleSheet.setProperty(`--${this.name}`, `${this.value}${suffix}`);
+  }
+
+  inputs.forEach(input => input.addEventListener('change', handleUpdate));
+  inputs.forEach(input => input.addEventListener('mousemove', handleUpdate));
   </script>
 
 </body>