Gameplay video by NostalgicGames - Commander Keen

Commander Keen was one of the first ID Software's games. It was a side-scrolling platformer set in a kid, happy theme. The game was released as a shareware, and it became very popular (so popular that ID released six expisodes). The game can be edited using original TED5 editor (used by the makers to create Keen), and a few other fan-created tools and editors.