the diffuculty was easy at the start, but by level 3 or 4 it had gotten very very hard.
although by the time you're at 9 or 10 then it's just ninjas and on levels 11 and 12 if you get 2 dragons and a ninja then you might as well go make a cup of tea or something.
it is a really good, fun game, with only a couple of minor problems which i shall overlook because the rest of it was great, and i'm nice like that.
1. all the defenders had were attack and range - how about something like rate of fire or something.
2. glitch!!! the health bar and mana bar had no idea what number it was on, they just jumped back and forth like pixies in a meadow. ya might wanna fix that.
3. glitch again!!! on almost every level that i used them, one of my mages turned crazy. wherever he was on the map, he sent balls of blue at the enemies for the whole time - it didnt actually do any damage until they were in his range, but it was still fun to watch. also, as you know, every time someone attacks they gain exp, so his was flying upwards. it didnt really need to fly upwards, though, because as soon as i'd clicked his position and he had started firing, he magically had 4 attack anyway.
i think you might wanna fix that too.
all in all though, brill game.