AdventurOS is described as "a unique RPG/metroidvania adventure", albeit one with a twist: the entire game, from the levels to the enemies, is based on the contents of your computer.
How? The game scans as it plays, and "interprets" each file differently. Imagine a music player's visualiser, then, but instead of making colours and waves, it's making rooms and monsters.
Each folder is a room, and the contents of that folder become what's inside. If you're not following, the trailer above shows you how it works, and what the game generates as a result.
If you're worried about what the game would do to those files, the devs say "The game will only index a folder when entered, and it only reads the information while being inside it. The game is not going to change any file except the ones inside the game folder."
Having passed its funding goal on Indiegogo, AdventurOS will be released on Windows, Mac and Linux.