Spout is a mini-version of Upper Hand played on the Shibumi set. Each player starts with 15 balls, and the board starts empty. Players take turns adding a ball of their color to any board hole or 2x2 platform. If the move completes a 2x2 platform containing at least three friendly balls, then the player places another ball on the platform; if that move completes another 2x2 platform containing at least three friendly balls, then the player places another ball on it, and so on. It is possible for a single ball placement to complete multiple friendly-majority platforms, in which case they are each completed with a friendly ball.
A player wins if it's their turn to move and they have no balls remaining. This can occur mid-move when a majority 2x2 platform is completed or at the start of the player's next turn.
Spout is similar to Upper Hand except that a 4x4 board is used, no "wild" ball is needed for the opening move, and there's a next-turn delay on the winning condition (which avoids a significant first player advantage).
For the three-player version of Spout, each player starts with ten balls and only two friendly balls are required to own a 2x2 platform.