Sometimes it lags when i hit Attack and attack do not apples.
controls are confusing. I can advise making space bar to hit and arrow keys to navigate.
Difficulty is to much for first level and i did not went further. Rates to fire are very often for red guy, shooting eye.
In general i love the style and music. Make it easier on first steps and it going to be nice. Add some save points.
Character appear and animation may be better. Add some colors for his dress (red, violet, blue). Draw some white trails for attack animation.