Pretty fun, pretty difficult. I like the challenge and I think this makes good use of the Metroidvania style despite its small size. I'm not super keen on how everything handles, though - I don't get as much response from the commands as I'd like, and in my opinion it'd make more sense to map jump to the up arrow and reserve Z for entering doorways, since you're doing a lot more jumping. The boss fight that gives you the laser upgrade was fun, but there's not a ton of visual feedback when enemies of any kind take damage so I was left wondering if I was making any impact at all until the boss died and the upgrade dropped. Overall though, I really dug the game.