Black Monolith Room

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The Black Monolith Room, referred to in the game's files as 'Ritual', is a mostly empty room which has red markings on the floor, identical to those seen on a Treasure Map.

The treasure map has an indication of where to stand in the room in 3D space, and a Tetromino Input Code, which, when input on the indicated space, will summon a large black monolith. The correct solution to this puzzle is not currently known, and was discovered by brute-force. To make the monolith disappear, leaving a Red Heart Cube in its place, the player must stand on the opposite marking on the floor, to the one used to summon it, and input Down Down LT RT RT A Up.