Friends on your Wi-Fi join at
Your own ROMs: NES, SNES, Genesis, Master System, Game Gear, Game Boy, GBA, or arcade .zip. Each one becomes a machine in its room.
Or copy games into the shared folder \\pi\roms (on Tailscale: \\pi.tail2c863e.ts.net\roms) — they appear on their own.
Make an account to keep your character, quarters and tickets, and get them back on any device.