I discovered it is much more rewarding to put a level cap on your heavy turret early on before allowing auto-upgrade so that it requires less participation from the user. And later you can upgrade it yourself just for the reassemblies.
Umm...a little hint, if you click on the follow us button and click on all four options (twitter and fb) just let the window open and you get the 1000 coins......no need to actually follow them :P
can you write please what is written in stats window next to playtime?