ANy tips for how to pass the special holiday Gremlins level? That 2000HP dude wipes me out every time. First I kill the gremlins by what I assume is Merlin's place, then I run down the road to the left (looking at the screen), then towards the "entrance" where -10 skeletons and that 2000HP dude are. I'm only lvl 13 abut have made as many upgrades as I can to my hero and other units. Any tips? What's the deal with only being able to place 4 units? The gremlins battle only seems to have a place for 4 units even though the prompt says 0/6 (or 0/10).