10 Infuriating Video Game Mysteries FINALLY Resolved Years Later
2. Black Monolith Solved (But No One Really Knows Why) - Fez

Fez is a cutesy game in which you go from room to room and solve puzzles.
Until you reach the Black Monolith, aka Fez's, if not the entire gaming world's, greatest unsolved mystery.
When Fez was originally released, the Black Monolith puzzle quickly gained a reputation for being unbeatable. The chamber gave no hints as to what the player was supposed to do, and every input you gave seemed to have no effect.
The puzzle stumped every player that came across it, and since the room itself was quite ominous with the giant black artifact looking above the player at all times, it eventually caused the Fez community to begin theorizing about it.
Entire subreddits teamed up to either try and solve the puzzle or discuss whether there even was a puzzle at all! Finally, through a little bit of code-cracking, some dedicated fans discovered a solution to the puzzle, putting most of the speculation to rest, but that said, it is still unknown to this day what the logic behind the puzzle is.
It seems like every answer just births more questions, but at least it's nice to know the Monolith room can actually be solved.