Trackmania is a highly-customizable car-racing game renowned for the insane videos players generate, showing off feats that would be impossible or absurdly dangerous in real life. Feats such as showing 20,000 cars racing simultaneously around the track.
Graham Smith explains at RPS:
The video is the culmination of half a year of work by organiser L4Bomb4, who collected the replays recorded in Trackmania United Forever and Trackmania Nations Forever, then converted and rendered 12,000 of them in the newer Trackmania 2: Stadium. "Unfortunately, the skins of the cars got lost in the process, but I could render with 12k cars at a pretty high quality without the game crashing," writes L4Bomb4 on the video's YouTube page. Another person, Danixks, edited the video and used a compositing technique to include 8000 further replays that would crash the game if rendered at the same time. The result is 20,000 cars on a single track.
It really must be seen to be believed: there are so many vehicles they merge into a bizarre fluid, spilling and splashing around the game's vast arenas.