I'm looking to make a multi-player platforming game using UDK. I'm currently doing feasibility research, to make sure I will reasonably be able to do all of the technical things I want to do. The first major hurdle I've come across without being able to find as answer, are one-way platforms.

That is to say, platforms through which a player can jump up, but not fall through (unless they choose to). These are commonly seen in games like Mario, Kirby and Smash Bros.

Does anyone know how such a system would work within UDK? I can think of solutions that might work for single-player, but not multi.