Enjoyed playing! It took me a bit to figure out the worm projectiles, they have a larger hitbox than the circle it seems. I was able to beat a couple bosses after a few failed attempts.
I was able to buy the multi-shot upgrade, but it was immediately lost entering the next room. It was fun while it lasted :P. I noticed that plant pickups didn't seem to stack, so I think some of the upgrades were impossible to buy.
The art was nice, I kinda liked the 3d floors. I agree that sound would really have elevated the experience.
Great job!