NY00123's first abandoned CK4 level pack
NY00123's first abandoned CK4 level pack (albeit it would be considered as more of a mod) features 4 levels, although only 3 of them are complete. Sand Yego was edited to include an area for testing out the switches. Most of the graphics in the mod are flipped, and one-way passages are included.
Two of the levels were featured in Buried in Oblivion.
Spoiler warning! This shows the whole levels.