The gameplay is pretty fun, I like that you can shoot a lot and watch the enemies get hit in one hit. The sound effects and being able to see the bullets and fire also added a lot to this.
I think to make the game feel less repetitive I would maybe only have one enemy in the first level, and add the second later, or add another one (a shooting enemy would be cool in my opinion). It could also add to have some type of upgrade apart from the health, for the weapon and yourself.
I also think it would help to have some hint about where the door is when the exit opens (not necessarily something that gives it away, maybe just an arrow in the direction).
It is very easy to finish the level and then get stuck for a long time looking for the door, and since the enemies come back after being killed it can get a bit frustrating.
The visuals were pretty cool, I especially like the bats and their animations.
I think a few decoration for the rooms would help a lot in making each room feel a bit different.
Not sure what the garlic does, I assume it adds score but I would explain it to the player.
I enjoyed the sound effects, they added a lot to the feeling of responsiveness from the game.
Background music was a bit missing but there was also something nice about just hearing the shooting sounds :)
Overall this was a fun game, good job on it!