Create a new game instance for a given family. Returns initial state to pass to subsequent calls. Variant can include flags like "grand+random" or "standard+drops".

Game family name (chess, draughts, go, reversi, shogi, xiangqi, mancala, morris, hex, landlords-game, backgammon, standard-52, bavarian-32, flower-48, double-six-dominoes, mahjong, standard-dice, agon, asalto, chaupar, dou-shou-qi, fanorona, halma, nyout, pachisi, royal-ur, senet, stern-halma, surakarta, tafl)

Variant slug, optionally with flags (e.g. "grand", "grand+random", "standard+drops")

Optional RNG seed for deterministic games