add audio listener that offsets vertices of hand by average volume, add start button that plays the music

index.html

@@ -20,6 +20,25 @@
       >
         Loading model: 0%
       </div>
+      <div
+        id="startButton"
+        style="
+          display: none;
+          color: #efefef;
+          position: absolute;
+          top: 50%;
+          left: 50%;
+          transform: translate(-50%, -50%);
+          width: 80px;
+          height: 25px;
+          border: 2px solid #efefef;
+          text-align: center;
+          padding: 20px 40px;
+          cursor: pointer;
+        "
+      >
+        BEGIN
+      </div>
     </div>
     <div
       style="