Ok. I was playing a match on tic-tac-toe when I noticed the towers that you can build. Unlike most engi-buildable structures this one was built in "stages". First the base of it, then the dome, then the tower above it. Interestingly the second and third pieces would only become visible when the section below it was destroyed. And when you destroyed the bottom section, all the parts above it were destroyed reguardless of their own health remaining. My question is how was this done? It'd really help in my new map.
I'm about to upload the source for tictactoe, so hold on a few minutes and you'll be able to download it. Basically, it uses the "onDeath" output for buildables (not in the standard fgd, you have to add it yourself) to disable the sections above. It's easier to see if you look at it in the editor.
Here is the source. You should be able to work it out from that. If not, I'll be writing a tutorial on the wiki for it soon, which should be a comprehensive guide. UPDATE: Here is the guide. It should work, let me know if there's any problems with it. For the moment, it doesn't deal with objects which change teams.