diff --git a/canvas-grad.html b/canvas-grad.html
index 2bdf3f4..e5da14b 100644
--- a/canvas-grad.html
+++ b/canvas-grad.html
@@ -47,7 +47,7 @@
         x = event.clientX, 
         y = event.clientY,
         rx = 600 * x / width,
-        ry = 600 * y / width;
+        ry = 600 * y / height;
         
     var xc = ~~(256 * x / width);
     var yc = ~~(256 * y / height);