I am up to Snowfall Mountains and only onto about 2nd or 3rd level and insufficient funds to even buy a tower so hence they just march right into the castle, ridiculous, no hope of stopping them without any defences. It takes playing levels over and over again to earn enough diamonds to upgrade your spells, increase cash in the beginning and towers let alone have enough diamonds to play the game with. I feel very ripped off with this game. I want to enjoy the game. Even though I have upgraded a lot of the towers, spells and money I am still being overrun no matter how many upgraded towers I have in place the castle is still being invaded. I have enjoyed it but want to be able to play what I have paid for...
I am only up to level 15 which has insufficient funds to build towers to start with, insufficient tower bases to build on near the time machine to protect it and just overwhelmed by dinosaurs before you can even build up any towers. I know I can keep coming back and replay over and over but also takes soooo long to build up any DNA to upgrade everything. Waste of money...