??Baba is You is a puzzle game where the rules of the puzzle are part of the puzzle itself.
In each level, the game uses "Text" tiles to write out the level's rules: Wall is Stop, Rock is Push, Flag is Win, Baba is You. Text can either reference tiles in the level (Wall, Rock, Flag, Baba), a type of behavior (Stop, Push, Win, You), or be a syntax piece (like Is). The objective of every level is to reach a Win tile.
The trick: the player can move the Text tiles around. Every level (except the one shown above, 00) is solved by rearranging the rules of the puzzle until you reach a Win state. As the game progresses, more and more types of Text are introduced, slowly ramping up the levels' complexity.