Keen 60: Kreeg Crisis!
Keen 60: Kreeg Crisis! is a Keen 4 mod released by Levelass. The mod takes place after the events of Underworld Ultimate. Pogoing, jumping, and shooting are disabled, which makes the mod less like a platformer and more like an adventure game. The ending conditions of this mod is to find a switch (which is found in the bottom of the level), and then flip it.
The mod is also notable for starring Mortimer McMire, now president of the United States. While not authored in any way by the creator of Keen 58 and 59 its canonicity in the world of the mod series has not been repudiated.