Please watch this link before continuing:

I've bumped into this video by watching some kismet tutorials from 3dbuzz. And what I want to ask about this video, are 2 things:

1 - somewhere in the middle, the player picks up a 'key'. How can you produce such a sequence, and how can you let a mesh just suddenly disappear?

2 - towards the end, the player receives a 'you will die here' phrase, and then all of a sudden the FLOOR lowers. How is it possible to move a brush like that? If that's not possible, how did he manage to fake the floor brush with a mesh then?