This is a really fun one, with a great idea! The art is really nice too. Two suggestions though
1. A clear indication of when the character can shoot again would help. I had trouble timing my shots because there was no clear way to figure out when I'd be able to shoot again other than just feeling it.
2. A way to quit the game? Maybe I'm just stupid or hit a bug or something, but I tried a lot of buttons looking for a close game option somewhere. Couldn't find one. Had to tab out and manually close the window.