Anyone have any strategy for beating Desktop Tower Defense on hard?

Do I go mostly squirts or what?

I usually build mostly squirts a few bash a few frost and a few swarm towers.

I think the tower placement is just as important as the type of tower you are building. I make dense mazes, it seems to work for me.

Just takes some practice.

I usually try making a huge maze with mostly squirt and frost. I build up a bunch of air towers, too but I still can't consistently kill those flying bosses.