Make a Register/Login page using html and then use it to log into a Unity Game,Hi!

Hi, as the question states, I need to make a Register/Login page, specifically using HTML/CSS and then use that form to register/login users for my unity game. I really don't want to make the login form in unity because of how bad it looks.

So for example, you open my website, register or login and when you successfully do so, the actual game with the corresponding scores, coins, level number specific to the user loads up.

I am relatively new to Unity so I don't know how to do this. Any help would be appreciated,