Move the pink point to rotate the configuration. Adjust the conics with the white points.
Poncelet's Porism from 1822 is one of the most fascinating theorems in projective geometry.
It states that if two conics have the property that there is a polygon whose vertices are on one conic and whose edges are tangent to another, then there is a
continuous family of such polygons. In other words, this incribing and circumscribing polygon can move around the conics.
In the animation you can play with this effect.
Two confocal conics are given and a starting point for creating a Poncelet chain:
a sequence of points and lines that forms the beginng of the Poncelet polygon.
By adjusting the positions of of the conics various Poncelet polygons (and Poncelet star-polygons) can be created. Moving the pink point exhibits the continuous movement
Experiment: Play with the position of the white points to generate Poncelet $n$-gons for various $n$.