It's a very novel concept (at least for me) and it's cool to think all the different ways this could be used. The arm wrestling game here is simple, but I think suits well for a party game of sorts. The sound effects are fun and add to the party game feel. Of course, an offline mode could be a pretty crazy option to have, imagine half a dozen people on the same keyboard.
Hey there! Thanks! Actually it does have offline, of sorts - as long as you're on the same wifi, you can add as many people with smartphones as you want, so there's no need for a keyboard even! Everyone gets their own controller on their phone. It's hard to show in a screencap video, but I've placed browser windows emulating what people will see on their phones to illustrate this.