For everyone wondering why the google sign in is required it's because the "app" gives you 5 free tokens to play with. It needs to be able to track that and just using google as your identity solution is way easier than rolling your own.
"Sign In With Google" -- nope! Not drinking the verification can for your novelty toy. That's how people's data got scraped off Facebook by Cambridge Analytica.
Also thought it was a joke. Absolutely not signing in to google for an unknown app meant as a novelty, and I can’t imagine that’s necessary for this to function so I think it’s fair to say it’s a bad design, if not outright malicious.