Dang, this game just feels so good to play. Bangin' music, good sound effects, satisfying gameplay loop, simple but easy to read and appealing visuals. Excellent job - tons of polish for a monthlong jam.
I see what you're going for with the weapon switching. It's potentially a cool mechanic to remove the player's weapon swapping agency. But I think it needs some tweaking. I only got to use the pulse gun and the shotgun for most levels, and I barely saw the sniper rifle. I also didn't have to vary my strategy at all based on the weapon. I think it'd be improved if 1. the weapon order was random 2. you have to swap weapons every time you run out of ammo, even if you upgrade them 3. there's a bigger difference between weapon types. Maybe the laser gun is weaker but sets enemies on fire, or the sniper rifle penetrates multiple enemies. And, it's cliche and inaccurate, but the shotgun only deals damage up close and makes you get dangerously close to enemies.