A survival game inside a house, an apocalypse happened somehow, but the player doesn't know how, all you hear are knocks on the door, the objective of the game is to set some traps for whatever is coming to catch you, home alone vibes
Maybe it could be a bunker that the player lives in. So the player has been living there for years, but then they hear something happen on the outside (like an explosion or something), and after a while the knocking starts.
I had this idea for a game once where the main character lives inside a mix between a tank and a bunker. Then a nuke explodes. The souls of those that died then try to kill the player, the only survivor of the explosion, whom all the ghost are jealous of. I never finished this game though.