Changing the circles to semi-circles

Hello there!
Spun is a lovely theme! I’m really glad that I have found it.

I’m wondering if there’s a way to cut the circles in half, and make semi-cicles. I know it is a bit weird but it would mean a lot to me if anyone could help me to make that happen.

I’m a newbie. I thought to add a rectangle in html/css and hide the upper half of the circle behind it.. but I don’t know..
Can anyone help me pleeease?

Thanks very much! Loads of love to the creators. Really an amazing theme!
best wishes
[ No bumping please. ]