Kishotenketsu
Also said as Kishōtenketsu, Four-step level design, Ki-sho-ten-ketsu
A four-part structure from Chinese poetry and Japanese four-panel comics: introduce an idea, develop it, twist it, conclude. There is no conflict required. In a level, one mechanic gets those four beats and then the level ends.
It stops levels being a mechanic that simply gets harder until you are tired of it. The twist makes you think about something you thought you knew, and ending right after it means the idea never outstays its welcome.
Say it
“Give the moving-platform level four beats: one platform over safe ground, then over a pit, then two that move on opposite beats so you have to wait instead of hurry, then one quick victory lap. Then end it.”
Where you’ve seen it
Koichi Hayashida, director of Super Mario 3D Land, described this structure for its levels in a 2012 Gamasutra interview: learn a mechanic, use it in a harder scenario, something crazy makes you rethink it, then show mastery. He likened it to four-panel comics.
Not to be confused with difficulty ramp
A ramp asks the same question faster. Kishotenketsu changes the question at the third beat, and may even get easier there.