Age of Empires: Castle Siege — The player maintained and developed a castle, which produced resources that could be used to train and improve buildings and troops, as well as research new technologies. Trained troops were used to attack other players' castles to plunder their resources and earn crowns, the game's scoring mechanism. Upgrading buildings was necessary in order to generate resources faster, store more resources, more effectively protect the castle from enemy attacks and unlock new technologies. Researching new technologies gave players many benefits, such as additional crowns if they won and a reduction in the resources that could be obtained from the player with each attack. Players could also form alliances with each other for various social and strategic functions, such as supplying each other with aid forces that helped players defend against enemy attacks.