Congratulations on your first full gamejam game! The art style is pretty cohesive all around. I thought the "Wrong hallway" text was funny, and having nukes inside of the pits instead of it just being a pit is pretty original! ;p
Some gameplay things:
Other people have mentioned it but I miss some sound effects. The player also needs a (short) invincibility time as I lost 3 hearts in less than a second while getting shot. I found I could just jump on top of the enemies and pretty much skip needing to shoot them entirely. I could also alternate R/Space to just constantly shoot without ever needing to reload. This is why reloading should take some time before it completes.
Good job on finishing a game and I think you can be proud of your gamejam submission! :)