These are the button mappings for an Xbox 360 controller. The emulator is a JavaScript Game Boy emulator. This is loaded on the Chromecast through a simple html file (called the receiver in the repo).
In the former vein, [antirez] has ported a ZX Spectrum emulator to the Pi Pico ... low resolution screens and minimal buttons. After all, very few Pi Picos come with a full QWERTY keyboard ...
Once downloaded, double-click on the installer and follow the on-screen steps to download and install the emulator. Next, click the Install button and let the emulator load. Go to System Apps ...