“I remember I was 4 or 5 years old, and I went on a helicopter ride, and it was one of the coolest things in the world,” he said, so he knew he wanted helicopters in the game, as well as some sort of clockwork world. And since the Apple II’s games were all very simple screens, “I wanted a very large world that I could really get lost in, and feel like it was that large.”

He made two tools to build the game world: Chedid was a character editor, which was “really primitive,” he said. Wedit lets you scroll around the world and place the characters from Chedid. “Wedit eventually evolved into Sim City,” he said. “I was scrolling around the world and having a lot of fun with it.”

Read what else Will had to say during his GDC 2011 speech over at Gamasutra!