Here's my entry for the latest round of Inkwell Ideas #GeomorphMaContest.
It's called Block Runner. Here's the blurb for it:
All the entrances of the geomorph open into a large chamber. Running along the length of the middle of the chamber are 8 giant blocks. In the floor, beneath each one, are channels that run the entire width of the room. In each corner, there is an alcove. Inside each alcove is a large metal lever. As soon as someone walks 3 squares into the chamber from any direction each block begins moving rapidly along its channel. The blocks start moving in the direction shown by the arrows, and then change direction when they reach the end of their channels. The blocks move 1d6 per round. Any character hit by a block will take a lot of damage, but you may allow a saving throw or similar and let them dodge a block that crosses their path.
There are alcoves in the middle of the perimeter walls that offer some respite from the sliding blocks. However, two of the levers in the corner alcoves have the potential to make them just as deadly as the blocks.
If the levers are pulled they have the following effects:
Lever 1 - Doubles the speed of the blocks.
Lever 2 - Halves the speed of the blocks.
Lever 3 - Pushes spikes through the wall at A and B.
Lever 4 - Releases poisonous gas in a 20' radius at C and D.
The trap resets 10 minutes after all movement (other than the blocks) in the room has ceased.