The minerals and gases in the center are worth less than the other minerals and gases. The middle is also much harder to defend so I think it's fair to say that those center resources are there mainly for design. Adding sunken ground at this point is a bit too hard. However, I will see if I can surround the entire center with compound and use ramps in place of the current entrances at the center. This way, it should be even harder to defend the center since attacking units would be entering from high ground.
I wanna test it out with you though to see how it is.
