Long ago, I wanted to create something like this.

There is is a similar upload already, however, this one I believe is a much more modern coding as well as provides a bit more function for your needs and comes with a responsive design as well.

Features:

Built with TailwindCSS 2.0.3 (uses CDN)
Hash generated by timestamp using SHA256 Encryption
USGN & Accesskey Stored in cookies
Username
Data (avatar, user mode, country)


Requirements:
Any webserver like nginx, Apache
PHP 5.1.2+, PHP 7, PHP 8, PECL hash >= 1.1
Modern web-browser in case you using TailwindCSS

Configuration:
Configure index.php:18 line to your own website/domain

How can be used?

1. Users enter their USGN ID
2. They confirm ownership
3. Get redirected and authorized.


Users can logout using logout.php (which destroys cookies)

Changelog:
2021.10.24.
Checking if "accesskey" and "usgn" cookies are set for security reasons. Thanks for @ Skripter5000:
The form now only allows numeric inputs.

Where possible USGN ID is fetched by cookies to save traffic

@ Skripter5000: It can be fixed easily, I might missed that part.

Fixed.

this should not be used ; there is no check if the key is empty, because then the API will always return 1.