Tiles slide as far as possible in the chosen direction until they are stopped by either another tile or the edge of the grid. If two tiles of the same number collide while moving, they will merge into a tile with the total value of the two tiles that collided. The resulting tile cannot merge with another tile again in the same move. If a move causes three consecutive tiles of the same value to slide together, only the two tiles farthest along the direction of motion will combine.