That makes sense, but is Grasshopper really the kind of app you want to sync across devices? I sometimes work on mobile games, and we always have the issue of whether we should force people to login (and give us data) or play without the login. We obviously want the login to improve our chance to make money. But sometimes logging in causes users to quit the app. But we can let them play without logging in, and sometimes games do that to get players hooked and nag them to surrender some privacy later. But that is why we do it: to make money.