Wow! I'm not really a front end person who works with this kind of stuff, so I don't know the real use case of this versus something else.
But: I went through a lot of the simpler ones on the codepen (minus, plus, menu, etc.) and learned some awesome techniques that I didn't know, then recreated them from scratch and was able to create some of the more complicated things. tbh I probably learned more css in the last hour than in any other single hour of my life. Nice!
I present: crudely drawn "x" icon with a circle around it: