Hey I purchased this game, new, about 2 years ago. I've gotten pretty good at it now I want to build my own missions. In mission builder, I can build single missions only. I must be missing something for campaign building cause some slots say "unavailable." Like the link button for the campaign. Is there anything that I can download, so I can build campaigns? It is the best game I've ever played. I just want to have more fun with it. Oh yeah it never came with a manual that I could read.