This is no 20 GB video file, painstakingly pulled from a render farm. All of it was generated in real time by one tiny algorithm. And it's amazing.
Every Easter, the town of Saarbrücken, Germany, plays host to Revision, a demoparty where hundreds of programmers and artists get together for four days of showing off. This year, the demoscene group Mercury unveiled an incredible 64k intro called The Timeless. Since the file size is limited to 64 kilobytes, the graphics and music are all generated algorithmically in real time—this is called procedural generation.
"Demos" are snippets of graphics and music that show off the author's skill as a programmer. The term emerged in the late 1980s, when a cracked video game would begin with a short intro representing the group who had cracked it. But it's evolved rapidly since then, and today, demos are more like works of art—a chance to show off your chops. Just think of it as the jazz improv of the programming world.