This is the smartest horror game design I've seen in years, and the reason is counterintuitive.
Every horror game since Resident Evil has solved the same problem the same way: give the player a weapon so they feel safe, then take it away at key moments. Safety → removal → fear. It works, but your brain adapts fast.
Perceptum inverts the entire loop. Your only tool is a mirror that forces you to look at the thing you're afraid of. The mechanic that progresses the game is the mechanic that terrifies you. You can't advance without choosing to be scared.
The "close your eyes" mechanic is even better. In every other horror game, closing your eyes would be a defensive move. Here it strips your vision and makes you rely on sound, which your brain processes with far less spatial precision. You trade one vulnerability for a different one. There's no safe state.
Two developers built this. The entire AAA horror industry has 200-person teams trying to solve player desensitization, and two guys just solved it by removing the weapon entirely.
the end credits of Project Hail Mary featured authentic astrophotography images by astrophotographer Rod Prazeres, showcasing his captures of real nebulae structures