It's great! I would have loved to see a level where you can stack on top of 2; the mechanics simple but it works really well! Good implementation.
Unless you did do a level with stacking 2, and I just couldn't reach it. I got stuck on the level that had 2 of the little guys.
Didn't notice if it's there, but having a small grace period where you can jump after stepping off a ledge would be nice.