Tonight I implemented stairs and an ending for the game. You must reach the teleporter on the 3rd floor of the ship, and teleport to safety. I also added some more flavour text, fixed some bugs, and balanced some characters. At this point the game is largely complete. I'll spend some of tomorrow playtesting and adding any remaining polish and balance I think is necessary. I also want to add a rocket launcher which shouldn't be too complicated given I already have projectile weapons and explosions.

This screenshot shows the teleporter at the end of the game: