Idea taken from this repository
The border-radius property defines the radius of the element's corners.
Most of the time is used 4 values wich corresponds to top-left, top-right, bottom-right and bottom-left.
But is possible to insert 8 values that allow to create more complex shapes.
Explaning the buttons.
Simple and Complex are used to change to the 4 values or 8 values input.
Compact show the shorthand version.
Detailed show properties separately.
E.g. border-top-left-radius