Endoparasitic

Endoparasitic puts you in the body of a scientist whose three limbs have been ripped off by mutated lab subjects, leaving him with one arm and a parasite burrowing toward his brain. The lab is on a remote asteroid, the research that started this is unfinished, and getting out requires dragging yourself through corridors one painful inch at a time.

The entire interface is mouse-controlled to mirror the protagonist's one-handed situation. You drag yourself by grabbing the floor. You load your gun one bullet at a time. You inject vaccines manually to slow the parasite's burrow toward your brain — your health bar is literally the parasite's progress. Stealth sections and boss fights break up the corridor combat.

Miziziziz built the entire project around the constraint: you can't do two things at once, every action takes deliberate time, and survival is a question of how well you can plan room entrances to avoid getting swarmed. Four guns, varied mutated monsters, puzzles, and a story that gradually explains what the research was trying to do.