For lvl 8 I built in a line down the map about 3 or 4 turrets wide. Built a lot of air turrets towards the top clustered. when the two air waves came, I built two basic turrets way off away from my main line. Two air units will go after those far off turrets while your AA turrets smoke whatever comes after the main line.
I beat the turtle but it never updates. It also tells me I have unlocked a new race but that never updates either. 1/5 I've seen a handful of ppl with same issue but not help on how to fix.