I thought of a mod kind of similar to Portal. It’s a puzzle mod with some fighting. You are in an old broken-down haunted mansion full of traps and dead ends. You can press a button to temporarily turn the mansion back into what it looked like in its prime. Kind of like this: Go to about 1:08. You have to use this ability to get past all kinds of puzzles and help you fight enemies a lot like this. And maybe you can have some telekinesis abilities to make things more interesting.
So what do you guys think?