this doesn't make a good PC game. I appreciate the effort on the port, but no thanks. the difficulty scales way too slowly for me to sit here until it gets good. I'd ask for a fast-forward button, but what's the point? the aimless leveling works when I'm on the pooper with my phone, but here it's unfulfilling.
some tips:
the sooner you set the ninja's smoke bomb off, the sooner they come out of it. so set up defenses right next to the entrances and some right near the gems.
and chopping down trees for $ is incredibly helpful early on in battles.
the best thing to do is get many towers out and then start upgrading.