Very fun and addictive. Sound design is immersive. The controls are razor-sharp, and there are some cool visual touches, like how the dim room becomes slightly brighter when the flamethrower is on. The scalable enemy sprite made me chuckle--there is no theoretical limit on how big those bad boys can be. The tiny ones feel like nuisances, the huge ones feel like hulking brutes.
The only suggestion I would have is more variety: additional enemy types, additional items, exploration, etc.