How draw a spinner animation

[teto]

I would like to show a spinning animation like https://github.com/j-hui/fidget.nvim when some services are being run (e.g. when fetching mail). I am not sure of the best way to do that.
Should I use CSS animation ? if yes which one ? My other take would be to set interval to 0.1 and draw different characters each time. I fear it uses up too much CPU as there is no adaptive interval ?