Mostly pretty good. Cute style fairly well designed for the most part, decent sized
Issues:
Most of the power-up seem _too_ well hidden. The average player doesn't seem likely to get many upgrades
Would be nice to be able to remap controls (keyboards work better with jump mapped to up)
Third boss not giving a new ability is disappointing
The difficulty spike at the end is _brutal_. I'm pretty certain the final boss can throw out impossible attack combinations. And there's no checkpoints...