You mean the amount of used SemiSolid brushes in a map?
Well, I'm still not sure about that. Some people say, they should be used rarely, others say it doesn't matter. Take a look at the Paci maps, he used tons of SemiSolid brushes for his maps and they just work fine.
The hard part is, that a SemiSolid brush can cause HOM's even if it seems to be 100% correct placed, but on the other side they also can work without problems. In some maps I could solve a problem when changing a SemiSolid to solid, in other cases that didn't work.
In some little tests I got different results. Sometimes I had weird errors, other times all were well. In bigger, more complex maps it's not easy to find the reason for a certain error. When I have a map with some BSP errors, I check the geometry for possible bad things which could be the reason and fix what I've found. In some cases the map works fine after that, but I also got maps which I just can't fix, no matter what I try. Best example is the last one, Nightfall.unr. This map is just a nightmare and I tried over three days to fix the BSP, but all I got was a compromise. There are still errors, but they don't affect the gameplay.
BSP is really a science, well sure for me
I can do a lot of things in a map, but BSP is the hardest part for me. That also was the reason why I gave up to make maps
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