Tower Swap is a match-3, tower-defense game with a merge element. A player must build a defense against dragons that attack a stone castle every night. The king places materials in a playfield area in front of his stronghold, such as piles of wood, stone and ice. During each day, the player creates towers, ballistas, ice walls, cannons and other weapons by matching three of the same connected materials in lines.
The type of defense depends on the type of materials used in the swap. For example, three stones create towers and three ice pieces create ice walls. Some weapons only fire in certain directions, which means the player must move them around on the field to mount the best defense.
Unlike many similar games that require that a swap create a connected line, this game allows the player to swap materials and weapons without making a match. The game also offers an evolution element for weapons. The player can connect and merge three weapons to create more advanced, powerful weapons.
The player receives only five swaps or moves per day unless they earn more by creating treasure chests or matching four pieces of the same material in a row. They also receive a finite number of lives and lose a life any time a dragon hits the castle.
If the player runs out of lives, the castle will collapse. They can prevent the event by paying a fee with earned coin or watching an advertisement. If they fail, they must start over.