Procedural Generation
When creating an extraction coop horror game, I believe the most important part would be the levels that your players are exploring. So I thought it would be best to have a large pool of interesting rooms and have the levels be generated before play, based on these levels. As of right now, the game has seven interesting rooms, which I plan on expanding into closer to 20-30, depending on the sizing of the levels.
Mansion from Lethal Company
Factory from Lethal Company
Lethal Company and REPO have an ingenious way of keeping the gameplay loop fresh through multiple playthroughs. Of course, both of these games have procedural generation for their maps, which allows the players to experience unique gameplay. However, they both have map variants that guarantee players will have a unique combination of maps. Lethal Company, for instance, had the Mansion and the Factory. The Mansion typically has larger room sizes, wooden walls, and specific species of monsters. The Factory has thinner rooms, often walkways, metal walls, and a Battery that controls the lights.
These subtle differences in gameplay and massive differences in appearance create the feeling of going to unique areas, even though the player was in these locations every single time. The theming of my game is intended to be somewhat medical, so to uphold this, the first set of rooms I would create would be a Hospital. I believe a ruined hospital could give players a feeling of discomfort immediately, as well as play with verticality in a way that I think has not been experimented with a ton.