Good job with the graphics and level design. I enjoyed the lil man's walk cycle! :)
Gameplay wise, the mechanics work well for what they are, and breaking the red blocks with the hammers is a nice touch! However, its gets repetitive pretty quickly. To counter this, a little more visual/audible variety would be nice. If you have a chance to work on this more, consider adding some background music... maybe a different track per each dimension? It would also be really neat if the different dimensions had different colors schemes. If there are too many levels to do this... maybe come up with a few (5 or so? ) audio tracks/color schemes to cycle through every few levels! :D
-Sasha