Iris Fill
Scaling to 2.1 rather than 1 is what makes the circle reach the corners.
Usage
Publish
Meant for
Examples
On a Button
Scaling the circle to 2.1 rather than 1 is what lets it reach the corners of a rectangle. At scale 1 you get a circle that never fills the button.
The class is wm wm-iris-fill — the first half is the marker the trigger and reduced-motion rules hook into, the second is the effect.