How can I make this rotation fit to the circle?

Question

The code should make the dot follow a perfect circle,but in the lower right corner there's a small gap to the circle's border. How can I fix this?
https://code.sololearn.com/WsKQiqckHLin/?ref=app

Answer 1

border in the #background are actually moving the entire circle by 2px to the right and bottom.

you can alter the formula a little, or removing the border, or add box-sizing: border-box; at the #background element

Answer 2

Ohhhhh you're right
I totally forgot about that.

Thank you very much! :)