diff --git a/index.html b/index.html
index 4e4f3b2..9445867 100644
--- a/index.html
+++ b/index.html
@@ -150,9 +150,9 @@ <h2 id="score">Game Score</h2>
         }
       });
 
-      stage.onMouseMove = function (ev) {
-        rect.x = event.clientX - rect.width / 2;
-      };
+      stage.onMouseMove = function (ev) {
+        rect.x = ev.clientX - rect.width / 2;
+      };
       stage.mouseMoveOutside = true;
 
       createjs.Ticker.addEventListener("tick", tick);