Your target audience is anti-Google login lol, listen to the feedback! Great work
Lol I'm not the one who made this, I am just curious.
Yes! Also consider letting people learn without authenticating at all. Those who care to save state/progress can log in. If you had an opportunistic "great job on completing level 10! if you want to save your progress, register here" message, I bet more people would register as well!