Crystal Castles was Atari’s attempt at an isometric adventure and exploration game, unusual for the arcade setting at that time. Crystal Castles is one of the first games with an ending, again something that was pretty unexpected in an arcade game. While it didn’t sell nearly as many units as Centipede or Millipede, it is a great game with excellent reviews, and a true classic.
As with all Atari games of that period, Crystal Castles has a unique pinout. It uses a trackball, and is not capable of accepting normal joystick inputs. As a result the adapter provides a micro-controller based trackball emulation circuitry which allows for JAMMA joystick controls.