Well it had a 4, but with no way of restarting the game at the end, and having to rewatch the intro sequences to play again, drags it down to 3. Plus it's basically a glorified demo :p
It doesn't obey the mute setting either, UFO's still makes noises. Some spelling errors (but nothing really major), and it would be nice if the jump wasn't static (hold longer for higher jump etc).
Couldn't see any info about it ingame, but you can sprint through enemies, killing/damage them as you go. Actually a pretty good game in its simplicity.
Level 17 really killed what fun it had. Even when following the tutorial, the physics is just too random, sometimes the head just goes through the spinning block. And usually it just ends up throwing "coal" in to where the head is.