I like the concept and the artwork.
It would be cool to have some kind of music and sound (both are free):
- Sound effects, I use bxfr, it's an SFX generator that randomly generate sounds that can be used
- Music, I use Chrome Music Lab Song Maker which has a very simple UI and gives you good result in a few clicks
Also a little tutorial for each character would be cool.
Oh yeah, also I've noticed in past jams that having your game playable in browser and a simple thumbnail for the page makes people way more likely to try it (for me I bookmarked your game on Monday but had to reinstall my old laptop to play it because I'm not running unknown software on my real machine)
Hope this is not too harsh, overall I liked the game, good job!