Stronghold is the name of the 2016 FIRST Robotics Competition challenge. Two alliances of three robots each compete to breach the opponents’ defenses, known as outer works, as well as capturing their tower by first firing "boulders" (small foam balls) at it, and then surrounding or scaling the tower using a singular rung on the tower wall. Points were scored by crossing elements of the tower's outer works, shooting boulders into the opposing tower's five goals in order to lower the tower strength, and by surrounding and scaling the tower. More information can be found on Wikipedia.