The game is played on a board of 169 squares distributed in 13 rows and 13 columns; each of the two players uses different pieces, one of them shells the other one snails.
The objective is to make a straight line (vertical, horizontal or diagonal) with exactly 5 pieces of the own, or to capture five pairs of your opponent's.
The player who uses snails starts the game by placing a piece on the center of the board (done automatically); both players will make one move by turn. One move entails in placing one piece in an empty square of the board. The pieces inside the board cannot be moved again. To neutralize the advantage that the first player has, the first player's second move is restricted to playing three or more intersections away from the center of the board. If two connected stones of the opponent are surrounded at both sides by a stone of the player's color as a result of that player's move, then that pair of stones is removed from the board. The player who first creates five connected stones or captures five of the opponent's pairs wins.