I made a post-compo version of my entry, with modifications suggested by commenters:
- added sound effects
- added music (ambient sounds, actually)
- small fixes in walking animation
- small fixes in gfx: exit doors became orange/red, also you see part of the room when the door is open
- gameplay fixes: player health was replenished at the start of a level, now it is maintained through the game
Thanks to CplMustard, merthsoft, jfroco, dr_soda, Thomas, Benjamin for their insightful suggestions!