This was really fun. The character designs are very cute, and overall the visual presentation is crisp and expressive. Good music, also.
I really appreciate how fleshed out this game is, with multiple special abilities, an Options menu, and a little in-game encyclopedia. Wow! (Yes, as noted in the description, you should avoid checking the encyclopedia during gameplay due to a bug, but still.)
One suggestion--I can't help wondering if you could have gotten a more striking result if you actually used another color or two. Of course, monochrome is a deliberate style, also.