I'd have rated this considerably higher were it not for a substantial glitch I encountered after receiving the 'punch' ability. The caves that you drop down into, I was somehow 'transported' into the black filler space around the platforms and could only move around in it. Obviously this kinda screwed my game.
That aside though, it's actually kinda good. The controls need a touch of polishing as they ARE a little sluggish, but the simple graphics work just fine, the music is fairly cheerful and the overall gameplay seems fairly solid. Without that glitch I'd have happily delivered a 4/5 at least. You might want to look into that, because it's a bit of a game-ender as glitches go.