The player controls and defends a territory consisting of a wall surrounding a set of castles and cannons. Gameplay alternates between two time-limited phases, combat and building. In the building phase, the player attempts to repair the damage from combat and expand their territory. In the combat phase, they attempt to damage the enemy with their cannons. In single-player games, the player fights against a fleet of attacking ships, in multi-player games, the players fight each other with rivers separating the sides.
The game opens with an automated building phase in which the computer builds a wall around one castle. The ownership of a castle grants the player control over a number of cannons, and after building the wall the game enters a phase in which the user places the cannons within their controlled territory. When the building phase ends, combat begins. In single-player mode, the player is attacked by a number of ships that approach the player’s territory while firing cannons at their walls.
The player responds by firing their cannons at the moving ships; the relatively slow speed of the cannonballs requires the player to “lead” their targets. In multi-player mode, the players shoot at each other’s walls. The goal of the attacker in both cases is to make holes in the walls. Combat ends when the user sinks a certain number of ships, or in two-player, after a set time.