For starters, the original Line Rider was straight to Internet and probably free. Basically it was made in Flash (like most Internet games).
The objective is to get a sled from point A to point B. The sled slides on a line (yes a line), and before each slide attempt you basically fill in the gaps of the line. You fill it in to make ramps, speed ups and slow downs. Then when you are satisfied with it, you send your sledder down the hill, up the hill, over a jump, through a loop or whatever else the course has you do. You do not control the sled by traditional methods, it is the lines that control the sledder.
Its a challenging game for the mind and enjoyable once you finally get your sled to the end. However, its mainly trial and error. Sometimes you need to draw a longer jump, or a higher jump, or a speed up then a jump, or a slow down then a jump. Trial and error, some of the more advanced levels can take an hour.
The game has a top notch physics engine that makes for realism (as much realism as a sled on a line can be). This game isn’t worth $5 or even $0.01. The presentation is simple and it should have stayed on the Internet.