Two players, human or device-like, create squares by placing stones on the grid, one in each turn. Keep at least one grid point between corners. After finishing a square you must remove one of your opponent's stones. When only humans play, the second player can swap colors after the first move. Play online by creating an opponent and showing them the qr code. Or send the link with the paircode through another channel. If both of you use the same paircode you can start. Give yourselves a nice name in the Settings and increase the number of squares to win. When the game is over you can replay it from the log to see what went wrong. That's it for now. Go play.

Force Four is free to play. Feel free to copy and adapt the code. No registration needed and no ads here. Licence is CC BY-NC-SA — Share and adapt for non-commercial use only, with credit, under the same terms.