I played the game the first time on medium. I only had trouble on medium with 2 maps--- and only with round 3 on both of them. First map that gave me trouble was mission 3, Manifest Destiny. It is just the sort of map that needs to be done very quickly.

I blew away the elves on the first couple rounds, but round 3, they murdered me and kept doing it. I often got one shot killed. But I figured out what most of that was--- the elves are spawning and trying to attack during the opening animation. Skip it and go fight. Also gear up.

When I did it on hard, I wasted them very quickly. But that was because I was geared up and understood why that map was so hard to beat the first time around--- it's tight, lots of enemies spawn, and you have attackers that can get through your block. I murdered the map by using the cannon and getting above everyone. That let me defend my troopers while they ran around and got me everything. Piece of cake.

That doesn't work on manifest destiny (no where to get up above the enemy to rain death over the combat theatre). Just running very fast does on that map does though. Go figure.