The object of Star Castle, created by Cinematronics in 1980, is to destroy an enemy cannon which sits in the center of three concentric, rotating energy shield rings while avoiding or destroying ‘mines’ enemies that spawn from the core, pass through the energy rings, and then home in on the player’s ship.
They can stick back to the shield if the player maneuvers in such a way that a ring is between the ship and the mines. The player-controlled spaceship can rotate, thrust forward, and fire small projectiles. The cannon’s shields are composed of twelve sections each, and each section takes two hits to destroy. Once a section is breached, rings beneath it are exposed to fire.
The three homing mines will destroy the player’s ship on contact. The mines can be destroyed, but they are very small and difficult to fire on, and the player does not receive points for destroying them. Mines are revived when shield rings regenerate (some variants keep three mines churning constantly so that a new mine re-spawns from the core as soon as one is destroyed). As the player progresses through the levels, the mines get faster and faster, forcing the player to keep moving to avoid them.