This is a great idea and excellent for a first game. Art is simple but goes a long way, music is a great choice, and I like the system of powerups. The one thing I'm not into is the balancing. I think the windows for unlocking upgrades could be better thought out, and I really don't like the spinning attack. It doesn't really require any skill to dodge and once it starts the game grinds to a halt while you just stand there waiting for it to finish. That's an outlier though, and the rest of the game is well made and pretty fun.