Thanks, I'm glad you enjoyed it! :)
The web version is simply an HTML5-based Game Boy emulator. For this game, I used RetroArch with Gambatte core (you can download it here: https://toadking.com/retroarch/). For my previous GB game, Sheep It Up, I used GBonline (https://github.com/taisel/GameBoy-Online). Both work smoothly, but I find the sound emulation better and more accurate with Gambatte. Let me know if you need help to configure either of them for your own game, i'd be happy to help!