If you aren't going to play this game Co-Op with a friend, don't bother with this game. Orcs Must Die! was a great game and could be played alone. When you play Orcs Must Die! 2 alone, you notice something almost immediately; the design of the new levels is clearly built for Co-Op action with a friend. The early levels are easy regardless, and there are some fun new mechanics that you can play with (funneling the orcs along minecart paths) which is a nice change from the first game, where you just look for the best place to place your Swinging Maces. Sadly, once you get about midway through the game some of the interesting levels seem to have already passed. Most of the time through barricades or planning you could get 3 or 4 doors worth of orcs to run through one setup of traps, which is about what was needed to clear the levels on War Mage difficulty. Sadly, about midway through OMD!2, it seems someone decided to make a whole pile of symmetrical levels in which there is no common area to filter all of the orcs through. Fair enough, it must still be possible to do it alone right?
If you've played the first game, you can picture what I am going to describe now: Imagine a 6 square wide path. There is only a buildable wall on one side. The other side of the path has a few blocks of lava, which cannot be used because if you try to throw them into it they just fly clear of the lava river onto the symmetrical path on the other side (past the point where your traps would be). There is a small section with a ceiling on which to build ceiling traps but Swinging Mace now basically does no damage and just throws the orcs away from your other traps. If you spend all of your money on one side of the level, you might get lucky with a setup that can stop the first 2 waves using all of the right traps in the limited possible building areas, but what do you do on the other side? Fight the whole waves yourself with no trap assistance? Goodluck, it works for a few levels and then you just get completely overwhelmed, You never end up with enough money to defend both sides, and you need to spend what you get to build up your untrapped side, and the original side that you built to start is leaking orcs (a lot of them) every level.
There are a few levels like this in a row probably about 75% of the way through the game. You clearly need 2 players, so each can play their own separate game on their own side of the level. How is that fun?
The first game was great. This one, not so much. I've had enough.