Great fun! I especially love the mini-map you can move through when you step on a teleporter. You can tell a lot of love went into that.
It feels really good to play, and I only have a couple of very small comments:
The aiming reticle feels off. It doesn't quite feel smooth enough, and it should always be visible on the screen. You should clamp its coordinates to the very edge of the screen so that it doesn't get lost.
Is the ammo cap on the default pistol really necessary? I know there's more than enough ammo to get through dungeons even with killing all of the enemies, so I have to wonder what the point is
The camera could maybe front-run the character a little bit more -- especially when heading upwards. I walked into a new rooms and immediately got hit in the face with a projectile a few times, and it doesn't feel fair. Either that or you can give enemies a bit more time to wait before targetting the player when you enter the room.
Good fun though, I really enjoyed it! The artwork is great too and the effects are spicy.