When I select a quest, I get a pop-up with the description and the option to complete or close. I wish I could select another quest in the background to have that one become active instead of clicking to close first. Saves one click each time you're moving between quest descriptions.
Got to darwin level 89 (after completing the game) on Insane mode, and I still haven't received the Demise of Species badge. Very strange. Something is screwy here...
Overall, pretty nice. Minor nitpicks: music loop is a bit repetitive, mines can be hard to see on the screen, strange that some projectiles by bosses can be shot while others cannot, and a few spelling errors here and there. Very enjoyable on the whole!
A good concept, but I wish there was queuing of soldiers, tanks, etc. It would also be nice if you could use money to upgrade yourself between levels, or replay levels to make yourself stronger.