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?
I'm not sure if the descriptions to these games are run through Google Translate, or just lazily written. Call me a grammar nazi, but it doesn't help first impressions.
if you're having trouble, here's a tip: start with upgrading five pure mushrooms to the max. one of each element. upgrade them in the order of the monsters' weaknesses. and as for the skills, level up the money over time for faster upgrading.
it would be cool if the windows that show changing stats such as exp, hp, mp, age timer, etc. would actually change instead of showing the number it had at teh moment the window appeared, and not budging afterwards.
that is exactly what a boss fight should be like. no massive amount of shooting to lower the health. just intelligent use of the environment to destroy a special monster. if its just a matter of shooting it down, what makes it different from the other monsters?