Emufii

Emufii is an Android app that puts far-apart friends “in the same room” with a 6-digit invite code. It uses Android’s system VPN to build a temporary private peer-to-peer network between players, so the local multiplayer already built into 3DS, Switch, PSP, PS2, DS and Wii emulators simply works over the internet — no port forwarding, no IP juggling. The host picks a game and shares the code, the friend joins, and Emufii opens the emulator with the multiplayer parameters pre-filled. Since 2.0 (2026-10-06), DS local wireless can even go online via the WatermelonDS Emufii Edition.

To be clear about what it is not: Emufii is not an emulator and ships no games, BIOS files or emulator binaries — you bring your own emulator and your own legal dumps. Nothing is streamed and nothing touches Nintendo’s or Sony’s servers.

The README dedicates a “How it was built” section to the process: “Emufii is built with Claude Code… About 90% of the code was written with the AI, along with much of the research into how each emulator handles multiplayer.” The author steered everything else — design, test strategy, code review, real-device testing — and the app has passed a security audit. 784 stars on GitHub, AGPL-3.0, free.