Karateka, an early martial arts side-scroller published in the US by Broderbund in 1984, was a little before my time. It was created by Jordan Mechner before he went on to make Prince of Persia — a game I do remember thanks to the horror of sending that character to a bloody, pixelated death on a bed of spikes. Karateka however was an early hit, with later iterations making it to NES and Game Boy. And the original Apple II version included a delightful little easter egg from the early days of PC gaming — putting in the floppy disk upside down would boot up the game upside down.

This isn’t new exactly — people have been trying this trick for more than 35 years — but it was new to me, and I got a quick refresher today thanks to the magic of YouTube. YouTuber Geek with Social Skills was demoing the game, and got a note that he should try inserting the game disk upside-down. You can see for yourself what happened when he gave it a try — the title screen, intro, and game all display upside down. It’s a delightfully simple joke, and it took a surprising amount of coding to make it work.

According to Mechner, the game’s developers hoped that a few people would discover it by accident, and think their game was defective. “When that person called tech support, that tech support rep would once in a blue moon have the sublime joy of saying, ‘Well sir, you put the disk in upside-down,’” Mechner was quoted as saying in a recent profile, “and that person would think for the rest of their life that’s how software works.”

Developers, we now know, have had a weird sense of humor forever.

Mechner says that he didn’t think Broderbund would sign off on it because it would require a change to the assembly line. But the company did, and a little hidden gem of gaming history was made because the president of a software company had a sense of humor, too. I, for one, am grateful for that.