I made this great map ages ago that had a neat twist -- buildable space was at a premium so you had to immediately and constantly expand all over the map and claim as much land as possible. In addition to that, you only had enough res to fully upgrade one unit type, or partially upgrade a few of them, and all the unit stats were adjusted in interesting ways, like cats had mega range I remember (more comparable to actual catapults). You could get barraged by cats from like 2.5 screens away, through fog. And archers had pretty good range to start, but rangers/'zerkers were friggen madmen. That map was pretty much the shit, but I think only 4p. :< It's actually really difficult to significantly change up the attack/defense/hp/etc values without making things totally imba.
