how about remove the worker`s tunnel building abbility & give the tunnel network a weapon that can creat another tunnel in a limited range after a while,using the sneak attack effect...
&make command center be the 1st tunnel entrance
I had this dream last night(OH my brain...),thinking that be the real tunnel system...
That would be unbalanced. Then GLA could just keep making tunnels for no money that slowly go towards your base. Unless ofcourse you use money to activate that sneak atack tunnel...
Tunnel Dream..
