One of the demos I’ve carried across nearly all the platforms I’ve worked on is the rotating cube demo, typically with back-face culling (hidden line/face removal), perspective, and fast integer maths. The code has been ported to the Gameboy, CPC, PC, Atari ST and Scratch. On more capable systems I usually add filled-in polygons with simple texture mapping and Gouraud shading I first wrote this demo around 30-odd years ago for the Spectrum, and I …