Button selection shape

Good day
Thank you for this cool plugin.
I want to add two types of variations that people need to choose from on my product.
I want to keep the one round with a picture and the next I want to make rectangular (see link above).
This has worked with css but the problem I have now, is that the selection ring around the selected variant is rectangular and does not become round on the round variants.

How can I make the selector round on the round variants and rectangular on the rectangular variations?

Many thanks!

The page I need help with: [log in to see the link]