Design a move strategy, then watch one game or run a batch.
Each move: pick at random among the checked moves that can slide.
Moves to use Backups, in order 1. Up
Last resort (always on): if none of the above can slide, take any move that works.
Same seed + same strategy = the exact same game(s) · the strategy is a preference: when
it has no move of its own, the player still takes any available move at random · games
end only when the board is dead.