A poc password manager (no database)

Hi everyone, I'm a fullstack engineer based in Melbourne Australia. In a random afternoon I got this random idea

Why we trust a password manager platform?
The most secure database should be our own memory
(or kinda wrong haha)

I came to this idea which is I only need to remember my password pattern and a master password (or more like a secret key)

https://easypwd.vercel.app/

Here I assume my password format is
platform-domain__DoB

eg. facebook.com__01011900

and my master password can be password123

This is my first side project, feel free to leave any comment :)