Transparent circle + border gradient on css?

Question

css

Tell me how best to solve the problem? It is necessary to make a transparent circle and fill it with a border gradient. Preferably in pure CSS

Answer 1

example 1
example 2
example 3

Answer 2

C svg something like this https://jsfiddle.net/qn9qum8g/

Answer 3

https://css-tricks.com/examples/GradientBorder/
Making a square, rounding, adding a gradient border