Travelling focus

One ring moves between the controls instead of each control drawing its own.

Its x, y, width, height and corner radius each follow a first-order layer with τ = 50 ms, so it takes the shape of what it lands on, from a round 32 px button to a pill of 28 px and a field with radius 8.
It shows only where the browser matches :focus-visible, so a mouse click shows nothing, and with reduced motion it jumps.
The ring is decorative and hidden from assistive technology; focus stays on the real controls.