hahhahah in 13 challenge you cannot go insane and 4 times in a row computer has a card to send me instantly insane (instand death)...wtf....ooooo what kind of luck is needed here, by the way I finished everything except chall.13 and 15 :P
need a higher number of towers,you have only 4 towers (shootable) and with this amount of levels becomes too boring so more upgrades and more towers,from me 3/5