The “demo scene” is easy to explain: nerds making pretty visuals set to techno. Extremely talented programmers in the late ’80s and ’90s, largely European, figured out ways to make stylish real-time graphics presentations by squeezing out every bit of maths available from commercial PC hardware. What made them extra appealing to kids from that era was not only that they existed at the large demo parties thrown a few times a year, but with a decent modem, a healthy long-distance allowance, and a little luck, you could download the tiny files on your own home computer and run them yourself.
They may not look all that impressive now in the age of photorealistic CG and phones that can run 3D games, but back in the day these sorts of hacks were mind blowing. A Metafilter post collects many examples from over the years, while a recently released documentary, Moleman 2, (embedded above) chronicles the intersection of computer hackers and rave culture.