A good strategy is to get about 2 or 3 titans (air dragon and popo at least) grab a tank-like creature (orangutang, untamed beast, epic tank, etc) and then any other 2 creatures you like, for skills make sure you have stop time, shield and meteor, anything else is optional. Now to beat pretty much ANY LEVEL have all your creatures wait at your castle until your titans spawn, then send them all out and spam shield to protect them, everytime shield is about to run out replace it, sooner or later your titans will pwn any major threat or your smaller creatures will have taken out the castle. For some maps (goblin challenge etc etc) don't worry about your small creatures, make sure your air dragon survives and use meteor to clear any black goblins out of the way. Hope this helps
Finally beat cut through tip: set the game speed to slow.
Also I think I know why some towers don't target ghosts, I found that when a ghost went through one of my towers that tower didn't shoot at the ghost.
If your stuck on a level after the first bridge do the heroic missions to unlock the 2 hidden levels and then do all the modes on them to gain mega exp, i got 5.1k exp from 1 heroic mission on map 4
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