diff --git a/ff0fsum4zx.js b/ff0fsum4zx.js
index 7b6bd52..f0dd121 100644
--- a/ff0fsum4zx.js
+++ b/ff0fsum4zx.js
@@ -222,8 +222,8 @@ R3.CustomCode.prototype.render = function(delta) {
 
 R3.CustomCode.prototype.move = function(data) {
 
-    var x = data.x;
-    var y = data.y;
+    var x = data.x || 0;
+    var y = data.y || 0;
 
     x *= 0.0025;
     y *= 0.0075;