Premise: Castle Wolfenstein is a stealth-based action-adventure shooter video 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. "Beyond Castle Wolfenstein" is its sequel.
Hypothesis: Castle Wolfenstein was released on Apple II six months before being released on Commodore 64.