Obsidian Conflict Forums

I wanted to make a non-linear combat map with evolving geometry. Meaning I wanted certain events to trigger at specific points in the level, such as a floor having a 1/12 chance of collapsing into a sewer, or maybe a 1/3 chance a stack of crates will block the low road, leaving only the high road.

Could I get an explanation on how to do this?

http://developer.valvesoftware.com/wiki/Logic_case

The article is pretty straight forward. Hope that helps.