Guys stop whining about teh fast-forward button. The game doesn't need one. It starts slow, sure, but it picks up speed. And it has to go at a pace reasonable enough for you to catch the wolves with reinforcements.
try resetting your upgrades, and upgrading your hero and the spells section.
then boost the archers and mortars to the best of your ability. to beat mammoths, you need to use beserk when it's swarmed by soldiers and your hero, and you need a lot of ranged towers to bring it down.
the trick is to start in madagascar. i just beat the game relaxed by randomly ending up starting in madagascar. the disease spread to the far reaches of the world with only rodents, fever, and a ton of resistences. as bacteria.
cool game, but I hope that when you make expansions, they won't all require premium. Kingdom rush needs premium for all the extras, and it freakin sucks that way. if you make expansions, at least leave one or two bonus missions free?