
Knytt and Knytt Stories is a free 2D platformer that allows user's to create they're own levels and then share them with others. Levels come with a difficultly rating but there are some that even allow difficultly to be changed. It comes with a few playable levels but from there more can be downloaded from websites and played later.

I love the creative aspect of this game. The fact that it can be anything the level designer chooses and include anything. This freedom is what art is about and for this reason I find Knytt stories an art form.
Image 1: http://elitegames.wordpress.com/2008/08/08/knytt/knytt_stories/
Image 2: http://www.flickr.com/photos/tigsource/466489976/