Castle Wolfenstein is an early stealth-based action-adventure shooter arcade game developed by Muse Software for the Apple II. It was first released in 1981 and later ported to MS-DOS, the Atari 8-bit family, and the Commodore 64.The game's main objective is to traverse the levels of the castle to find the secret war plans and escape alive. Progressively higher military ranks are earned upon each successful escape with the war plans, and the game becomes correspondingly more difficult as each higher rank is achieved. There are eight ranks, beginning with Private, culminating at the rank of Field Marshal.