I think there's more you could have done with the level design to challenge the player other than just more enemies in a larger map. Also try learning about randomized pitch shifting, especially if you're only going to use a single sfx file.

Enjoyable game. I like the gameplay, its very simple but breaching the diffrent room layouts can still be rather difficult. Def a lot of room for expanding on it, with diff enemies weapons ect. The graphics are nice as well, simple but they get the job done. More sounds & music would be nice