For contests, I use the Codeforces m1 site mainly because it has a built-in dark mode, and sometimes the site responds faster than the main one. However, it has two really annoying problems:

1. Any announcement notification is shown multiple times repeatedly. ( most annoying ) prove 1

2. While submitting, if you click quickly multiple times, it submits the solution multiple times. prove 2

So I request MikeMirzayanov and Vladosiya to fix these issues (at list problem 1 ), or please introduce dark mode on the main site also I have also seen the first problem on the main site long time ago, but on the m1 site it occurs much more frequently and keeps repeating again and again.