As a kid, I used to carry around my Game Boy Color in a fanny pack. Partly because I was the sort of cool tween that owned a fanny pack, partly because Nintendo’s handheld console was a fair bit thicker than today’s smartphones. If, like me, you yearned for the day that someone made a Game Boy small enough to fit on your key chain, your dream has now been realized.

On Monday, engineer Jeroen Domburg, who goes by the name Sprite_TM, presented his latest creation at the 2016 HackADay SuperConference in Pasadena, California. The gadget is essentially a tiny computer running an emulator, so classics like Tetris, Pokémon Gold, and Super Mario Bros. Deluxe are instantly accessible without any fiddly cartridges to deal with.

The tiny circuit board powers a speaker smaller than half an inch wide, an ESP-WROOM-32 system-on-a-chip module to power those high-end graphics, and a tiny 150 mAh rechargeable battery. The one-inch color OLED screen displays 96 by 64 pixels, which is a bit less than the Game Boy’s 160 by 144 pixels, but Domburg found it didn’t make much of a difference.

The basic hardware means there’s not enough storage to hold too many games, but there’s some ingenious “cartridge swapping” going on here. That system-on-a-chip contains wifi support, so Domburg developed a system where, in the Game Boy’s settings, users can switch on the wireless radio, and using a smartphone or computer, swap out the games stored on the chip. Pretty sweet.

If you want one of your own, you’ll probably have to fire up the soldering iron. Domburg is planning to release the system’s source code on his website, but it’s unlikely to see a release in retail stores.

Never say never, though. If Nintendo has shown anything over the years, it appreciates the value of re-releasing old classics to cash in on nostalgia. The NES Classic, a tiny computer designed to look like the ‘80s era console, went on sale earlier this month and almost immediately spiked in value on eBay, reaching early markups on eBay of nearly 14,000 percent. On the handheld front, long-time Nintendo followers may remember the 2005 Game Boy Micro, which packed a Game Boy Advance into an exceedingly tiny package.

Nintendo has since abandoned Game Boy, with the DS covering the handheld side of the business and the Nintendo Switch looking like it may satisfy both handheld and home console users. But Domburg’s creation shows that there’s still room for improvement, even on old classic machines. Just don’t forget your keys.

Photos via HackADay/YouTube (1, 2)

Mike Brown is a London-based writer with a passion for tech, politics, and photography. After studying Journalism at Columbia University in New York, he returned to the UK to cover the news as it happens around Europe. His work has been featured in IBTimes, Neowin, Building Magazine, and more.