Idea #1: Horror game inspired by Hellstar Remina where you're watching the slow decay of society as some impossible threat approaches and numerous strange phenomena unfold as it approaches Earth. Eventually all leading up to you walking on the surface of the Hellstar-like thing.

Idea #2: Romantic visual novel where you are a girl in college and also a shotacon and you start encountering cute boys and you can romance them. Wouldn't be a passive heroine tho. Would play an active role in progressing the romantic element with the cute boys.

Idea #3: Game that is an art installation and there's only one copy of the game and once it ends, either through reaching a particular conclusion or getting a game over, it deletes itself. Maybe livestream whoever gets to play it. The artistically compelling being how it might encourage rumors or hearsay about the game, as well as encouraging people to make all sorts of speculation about what aspects of the game were never seen in the single solitary playthrough.