Radar

A beam sweeps the scope every four seconds; each contact flashes as the beam passes it, then fades.

How it's built

Range rings are empty rings with a border, every 4 lanes; the crosshair is four .vectors twelve lanes long.
The beam is the orbit-12 ring itself, painted with a conic-gradient and turned by a CSS animation.
Each contact is a satellite at a fixed bearing (.angle-N) on the lane of its distance. Its animation delay comes from that bearing, so it lights up in time with the beam.