I really love it! I think that you should always be able to hit things though, rather than waiting a second to be able to hit the object again. 

Pretty neat! I personally would prefer the default movement and shot speed to be a little faster, but it was certainly workable. Being able to shoot the projectiles out of the air was a very pleasant surprise, and I found myself reaching for that when facing certain enemies. I did run into an issue where I had a run that had no enemies in the level, or maybe they were just very far off? I ran around for probably ten rooms or so and didn't see any so I reset the game and then had enemies where I'd expect them.

Hey, cool game. I like the upgrade menu, the enemy variety, and the upgrades. The art is nice and consistent. The key system gives an objective other than finding the exit, which introduces some variety to each run.
I think a few small improvements that could go along way are: putting sound effects on a few more things like the upgrade menu, and putting a hitbox around each chest so the enemies can't walk through them.