Type a 40-year-old sequence of keystrokes on a specific Bank of Canada web page about a commemorative 10 dollar bill and the site starts playing an 8-bit version of the national anthem while tiny banknotes rain down your screen. This episode explains how up, up, down, down, left, right, left, right, B, A got there. In 1985, Konami developer Kazuhisa Hashimoto was porting the arcade shooter Gradius to the NES, could not beat his own game during testing, and programmed a shortcut that granted a full set of power-ups. He forgot to remove it, and because NES games were written in tightly packed assembly language, deleting it at the final stage risked breaking everything.

The code exploded with Contra, where it turned three lives into thirty and democratized a brutally difficult home port. Konami embraced the mistake as a brand signature, and la ...