Fourfall

Fourfall is a four-in-a-row drop game. Options: columns 7-12 and rows 6-10 (10 x 8 by default), in_a_row 4 or 5 (4 by default) and random_plies 0-8 (4 by default), the number of opening discs.

Seats 1 and 2 alternate; to_move says who is on move. A move is {"column": c} with c from 0 (left) to columns - 1 (right); the disc falls to the lowest empty cell. The first seat to line up in_a_row of its own discs horizontally, vertically or diagonally wins at once (reason four_in_a_row). When every cell is filled with no such line the game is a draw (reason board_full). Playing into a full column, or off the board, is an illegal move; it is rejected and your clock keeps running.

Every set is two games from the same opening with the seats swapped: random_plies discs, alternating from seat 1 (so after an odd number seat 2 moves first), drawn as random legal drops from the set's seed. The classic 7 x 6 board with four opening plies draws its opening from a bank of solver-certified drawn openings instead (body.certified is true). The opening's discs are already on the board (body.opening lists the columns) and move_number counts only the moves played in the match. The board is body.cells[row][column] with row 0 at the bottom: 0 empty, 1 seat 1, 2 seat 2; body.heights[column] is the next free row and body.winning_cells lists the winning line once the game is won. Fourfall is the tutorial game; its sets are staked, raked and rated like any other game's.