Yukiko Nakagawa started toying with a personal computer when she was a 6th-grader in the early 1980s — years before Microsoft introduced its first Windows operating system, and back when most people, let alone children, had never seen a PC.

Back then, Nakagawa, 37, says she originally wanted a Famicom games console to play with, but her parents — who run a metal-processing factory in Kanagawa Prefecture — instead gave her a bulky PC. Because she had "no other games to play," Nakagawa self-studied programming languages from computer magazines and started making video games on her own.

One of the games she ran on that computer looked like "Space Invaders," she says, but it was in a much simpler format and featured balls that moved around the screen trying to attack a block, and a rectangular block that players could manipulate with keystrokes to avoid attacks.