Karateka was my first published game. I spent two years programming it on an Apple II, mostly in my college dorm room and my parents' basement, and submitted it on a floppy disk to Broderbund Software.
Set in feudal Japan, the story couldn't have been simpler. An evil warlord had kidnapped your girlfriend and you had to fight his karate-trained minions to rescue her from his fortress. What made Karateka different was that it felt like a movie, with more fluid and lifelike character animation than any game before.
I adapted silent-film techniques I was learning about in my history-of-cinema classes at Yale - rotoscoping, cross-cutting, tracking shots - to the Apple II.
My goal was to create a game that was visually sophisticated, yet so easy to play that even a non-gamer could immediately grasp the story, pick up the joystick and and become addicted.
Back then, games didn't have marketing campaigns. Reviews and word-of-mouth drove sales until, by April 1985, Billboard magazine ranked Karateka as the #1 best-selling game in the U.S. With versions for Commodore 64, Atari, Nintendo NES and Game Boy, Karateka sales eventually passed 500,000 units. In those days when the video game market was less than 10% of its current size, this was a real number.
Karateka was a life-changing breakthrough for me. It proved to me (and to my parents) that making games was not only a hobby and passion, but a legitimate career. Its warm reception helped me decide, right after college, to go on and make Prince of Persia.