In what is probably the most impressive retro gaming-related project you'll ever see, Gregory Gaines, programming enthusiast and Google software engineer, created a Gameboy emulator within the familiar confines of Google Sheets. You can check it out in his blog post titled "My Attempt at Running a Gameboy Emulator in Google Sheets".
Emulators are software or hardware that let you run software designed for a different system, and Gaines pulled it off by replicating the Gameboy's workings within Google Sheets. This emulator faithfully emulates all the essential elements of the Gameboy system, including the modified 8-bit Z80 CPU and the 64 KB of memory. It even emulates other components like the LCD, timers, APU, serial port, and gamepad buttons.
Since the whole project runs within Google Sheets, it's effectively device-agnostic. Any machine that can open a Google Sheet can, technically, also be turned into a retro gaming device simply by opening up a browser tab, with no downloading necessary.
It isn't perfect. Due to limitations related to the Apps Script API, the emulator runs like molasses. So, unless you've got endless patience, don't expect to complete any Pokémon Red runs anytime soon. Still, those limitations don't keep it from being a truly jaw-dropping proof of concept.
You can even try it yourself! All you have to do is make a copy of the Google Sheets file, activate the script, and voila! You'll see a new "Gameboy Emulator" tab. Click on "Show dialog," and you'll be taken to the "GameboyScreen" sheet where the magic happens.
Check out Gregory Gaines' GitHub repository for more of his retro gaming projects.