Fluent Forms Payment Question

I'm watching the video attached here, and I see something that either wasn't explained or I don't understand.

The video shows how to create options for the payment using radio selections. You can see them at timestamp 3:02.

After switching to the Confirmation Message to update it with a link, the display changes; instead of Radio selections, you can now see boxes at timestamp 3:40.

Those boxes look much better, but how did they get this appearance?