Cuyo is a Puyo Puyo-style puzzle game for up to two players. The player controls falling blocks of various types which change with each level.
For example, in the first level, the player has to connect differently colored cartoon faces to each other. When enough blocks of the same type are connected, they explode. Usually the level goal is to destroy a certain number of special blocks at the bottom of the screen; these special blocks explode when blocks adjacent to them explode (in some levels, only when this is accomplished through a chain reaction).
Some of the more complex levels have
changing blocks (e.g., darkening over time, changing into a different state, only revealing their type occasionally)
changing environments (e.g., very quickly falling blocks)
different block connection requirements (e.g. blocks can only connect diagonally, different shapes of different colors join according to color once, then according to shape)
The player loses when the blocks reach the upper border of the level. This upper border is slowly lowered like a "curtain" (with a velocity depending on the level), forcing the player to reach the goal within a time limit.
The game's graphics and animations, while simple, are part of the player's motivation, since they change with each level. The constantly changing requirements make Cuyo different from Tetris, where the main variation over time is speed and scoring.