One-way through textures

[ULTRA Random ViruS]

How do you create them? I was thinking of making a map related to doodle jump from the ipod. If i don't, you might as well:
Steps:
1.Create the one way through brush. Add a killer on the bottom.
2.Jump pad mania.
3.Make some of those brushes move!
4.Make sure to cusion all those brushes so humans don't die from fall. 
5.Aliens can either join in or watch from a portal camera!

[your face]

Patch mesh.

[CreatureofHell]

Good luck.