The concept is interesting - timing a projectile with another falling projectile. However, the movement on different platforms is not well represented: it is not easy to tell background from the actual level, and that's not something you want the players to have problems with.
The graphics can be enhanced, and instead of the 'right' arrow, make it a space to launch or so. The mechanics of the 'sponges' was difficult to handle as well.
I couldn't pass the sponge level because of the mechanics there... Having different platforms with different capabilities, like speeds, jumps, etc... would be make it interesting later on.
Graphics can be enhanced as well :) but great job all together!