plat from top (door) from QuakeLab by Steve Fukuda is a Single Player level. This level is somewhat identical to Plat top start (like e1m3) from QuakeLab by Steve Fukuda, the main difference is in the way the Elevator functions.
The Elevator in this level starts on the top floor. When the player descends, it goes down, but then it rises back to the top. If the player is stuck at the bottom, they can trigger the Elevator to lower by walking near it. This is actually a hack done by manipulating Door properties as opposed to using normal Elevator mechanics.
Walkthrough
Step onto the Elevator straight ahead to reach the lower floor.
Gallery
Plat from top (door) from QuakeLab by Steve Fukuda