Margo is an abstract board game similar to Go, except that it's played with marbles which may stack upwards. A special capture rule means that captured pieces that support enemy pieces are not removed.
Margo is played by two players, White and Black, on a square grid which is initially empty (7x7 is the standard size).
Each player has an unlimited number of balls of their color.
Players take turns placing a ball of their colour either:
At an empty board point, or
Stacked on top of four existing balls (of any colour).
Players may not pass.
The game ends when the current player has no legal move. The player with the most balls in play wins.
Surround capture: After placing a ball, all enemy groups without freedom are captured and removed from the board, except for those which support enemy balls, which remain active in the game as zombies (only board-level freedoms are counted).
Over/under rule: A connection crossing over an enemy connection cuts it.
No-suicide: It is not permitted to place a ball without freedom, unless that move captures neighbours to create its own freedom.
Ko rule: It is not permitted to repeat the board position of any previous turn.
Swap rule: After the opening move, the second player may elect to swap colours in lieu of making a move.