thnx
I never done anything with variants, but they sound like things I should use more often. Can you give me some more explanation or point me to a site with a tutorial on variants?

About checkpoints, I don't think I set them automatically. The only thing I think I going to implement is an auto-save function. something like saving every 5-10 minuets. I already got some sort of crash-recovery. When it crashes is save instantly saves the map-file.