removing overflow perhaps?

sandbox/index.css

@@ -14,10 +14,11 @@
 
 #renderCanvas {
     position: absolute;
+    overflow: hidden;
     width: 100%;
     height: 100%;
     top: 0;
-    margin :0;
+    margin: 0;
     right: 0;
     left: 0;
     touch-action: none;