A Maker-Breaker game is a two-player positional game on a specified board 
with a family of target subsets
of 
. In the unbiased version, Maker moves first and the
players alternate claiming one previously unclaimed board element.
Maker wins by occupying every element of a target subset. Breaker seeks to prevent this.
In a polyomino achievement game, the board is the square point lattice and targets are allowed copies of a fixed polyomino. The snaky hexomino provides a six-cell example. On a finite board, Breaker wins if the board is exhausted without a completed target.
The illustrated partial position uses the snaky hexomino as the target, with blue disks for Maker and red disks for Breaker. Maker's upper blue disk creates two winning threats, indicated by dashed circles. Breaker can claim at most one of the two completion cells, so Maker completes a target on the next move. Green outlines mark the completed target. Only Maker's completed target counts. Breaker stones outside the illustrated region are omitted. This local fork illustrates an immediate win from a favorable position, rather than a complete strategy from the empty board (OpenAI 2026, pp. 5-6).
