Pulsar

Tap it to spin it up. Set its spin speed in the Splash tab.

A pulsar is a neutron star, the crushed core left after a giant star explodes. It is only about 20 kilometers across, the size of a city, yet it holds more matter than the Sun. It spins fast and sends out two beams of light from its magnetic poles.

Like a lighthouse, it seems to flash each time a beam sweeps past. Tap it to spin it up until the flashes blur into a strobe, each with a deep pulse, then it winds down. Set its spin speed in the Splash tab. The first pulsar was found by Jocelyn Bell Burnell in 1967, and the fastest spin hundreds of times a second.

This link opens it in the Playground. To put it on your own page, add the element and one script tag. Every option.