Regular icosahedrons are 20-sided polyhedrons formed out of equilateral triangles. As such, the geometry behind making one is slightly complicated, but the results in the case of this light-up device appear to have been well worth it.

The project’s write-up does go over how to actually model these faces in CAD but also provides the 3D print files if you’d like to skip to building your own. Two versions were made, including a super-sized playable die that illuminates RGBW LEDs under Arduino Nano control, and a second icosahedron large enough to be used as a lamp shade! 

A demo/explanation is seen in the first clip below, along with a better look at the electronics in the breadboard video.