Hi guys, I would like to know how I can mod buildings in the export_descr_buildings.txt. What I would like to do is make ballista ranges, catapult ranges, and siege works only buildable in castles. I have already tried editing this part out:

building siege
{
convert_to castle_siege
levels ballista_range catapult_range siege_works
etc

and just leaving in:

building castle_siege
{
convert_to siege
levels c_ballista_range c_catapult_range c_siege_works
etc

And no success, the game wont start up now so this is the wrong way Could someone be kind enough to explain exactly what I need to mod and what lines would I need to change. I have already tried looking for tutorials on how to do this but cannot find one.