This is a simple Kanban where you can add and move cards between 4 steps, to change to another project, just click on your project name on top right corner. Of course, this site is public, so another person can access your annotaions, so, don't put any sensitive data on it.
Please, don't try anything silly like DOS attacks or any kind of attack, because your are going to be blocked indefinitely.
https://github.com/AleixoLucas42/cardsgo