but if it uses oauth then it asks for login, yep? and i mean to use simple api, like idk. reading actual COOKIES? LOCALSTORAGE? VARIABLES?
As far as I know, neither cookies nor the localstore save the name of the account running the game (at least not the ones you can access):
https://itch.io/t/1330021/how-to-read-user-id-or-email-on-client