Line Rider is an internet physics toy.
It was originally created in September 2006 by Boštjan Čadež (also known as "fšk"), a Slovenian university student.
The basic concept is to draw one or more lines with the mouse on which a boy (referred to as dude or Bosh or linerider by the creator) on a sled can ride after the player presses the Play button. The game includes simulated physics, which means the track must be sufficiently smooth to prevent the character from falling off the sled. The author has said that he prefers the description toy to game, as there is no goal to accomplish, nor does it have an end.
This is the file that is the actual puzzle part of LR2 puzzles.