There's a reason people love this so much that a variety of fan remakes and patches exist for this, it's that good. Not only is it a great use of the lego concept (since you build your base) but it's pretty unique as far as RTS games go, most RTS titles pit you against an equivalent army, this pits you against nature. I can't think of another survival RTS though Dungeon Keeper is clearly an inspiration. Incredible atmosphere and some really unique features.