Made during the popularity of the horror game "Five Nights at Freddy's", a set of Mari0: SE mappacks were made based off the concept. This one was the most functional and polished of them, but also the least concerned with replicating its inspiration.
The mappack has the player closing doors in order to keep shadowy ghosts outside of their room, which houses a floating, blue crystal. If a ghost touches the crystal, it's game over. It is made more complicated by the two side rooms where the ghosts roam being completely dark, requiring players to step on a button to turn on the lights.