Good level design, sprites are interesting to look at and overall well animated. There didn't seem to be any audio, and I only was able to play the first level (assuming there are more), because there wasn't really a clear way to end the level, unless I missed something. Controls are adequate, it would be nice to have jump height variation based on how long up or W is held down. I did notice that when I ran into a mushroom, there wasn't really any death animation, it just kind of waited a moment and then put me back at the checkpoint.
Overall: could use improvement, but certainly shows promise