How to add rounded corners to lovelace cards - within a theme?

[Martin_Granger]

As far as I know, you can’t add styling for rounded corners in the Theme.

I did try to add rounded corners a while back - check out this thread I started:

Lovelace instant'ish CSS changes

Just trying to get my head around lovelace. Is it possible to modify a CSS file to make (relatively) instant changes to the front end? The way t looks to me at the moment is that I have to make a change to my theme.yaml then restart Hassio for the changes to take effect. This is obviously a massive issue if you are trying to build / theme something! Any clarity on this??

I have since given up!