Giaddon

Kohan: Immortal Sovereigns (an old fantasy RTS) had a slot-based system, which I always liked. Each city started with one or two slots, then could be grown to have an additional slot, up to five or six slots. There were always more buildings to build than could fit in one city, and each building could be upgraded into only one of several upgraded versions (a resource building could be upgraded to give more of that resource, or to give slightly less but instead increase the defense of units bu