Hmmm...
Well... It isn't so awesome. It isn't even as hard as you say this. I'm writing my comment while playing endless mode, and I don't even need to see that my two towers of upper left corner are eliminating every incoming soldier without any difficulties.
I don't see any "strategy" except putting every tower at upper left corner. There is no blocking path, no juggling between our towers, not even the possibility of selling them.
And I wonder why they have to get around this building, cause the entrance is two pixel near the goal. They're idiots.