As @Gary Willoughby says, it extensively procedural.

Also, there is significant hand asm coding involved, along with extensive knowledge of how many of the windows/platform of choice systems work internally.

There is also a 4K demo category, if you want to see even more extreme examples of compact code.

Some of the DemoScene groups release their demos online, where you can download them and play them if you want.

Conspiracy

farb-rausch

Also See Wikipedia on the history of the DemoScene

Note - a lot of the demos will cause your antivirus to freak out. Basically it seems pretty much all demos use packed .exe files, and most of the demo groups roll their own packers. Unfortunately, because a lot of AV companies are lame, they generally claim that any packed binary executable is a virus of some sort.