It's been done before
This is another side-scrolling space shooter. Pretty basic, not groundbreaking, and nothing I haven't seen many times before. The graphics were decent, nice clean sprites and bright primary colors, but a little more creativity might be called for. Try varying the enemy tactics and level backgrounds.
As for the levels...I played level 2 for 10 minutes before I finally gave up. There may be some bug issues here that prevent some levels from ending. If that was planned, I would advise that in the future you cut the length of the levels down to a MAXIMUM of 2.5 minutes.
Also, program the "small cannon" button so it can be held down and keyboard damage avoided.