Line Rider a 'toy' a university student created for a project. It is called 'toy', not a game, because you can't lose or win and rhere's no goal. Basically, you draw lines for the rider.
Here's the desciption fron the official site.
Line Rider was originally created by Boštjan Cadež, a Slovenian university student, in September of 2006. It almost immediately gathered a cult following and became the seventh quickest gaining keyword in Google. Since that time, the ‘toy’ has generated over 16 million views. Fans quickly noticed that they could create tracks, set them to music, and share them over YouTube.com. Currently, there are over 11,000 shared videos with many more to come. inXile Entertainment is extremely excited to work with Boštjan in order to reach the full potential that we feel the Line Rider application can live up to. Keep an eye on this site for more information from Line Rider.