The enemy AI cheats insanely... 3 times in a row there was a 50/50 chance of winning, the enemy won and then used a medium elemental stone every single time...
Great game, but i think the difficulty curve is a bit steep... I beat the first league easily, beat the second league easily and then lose the third league humiliatingly...
Why do Ninjakiwi have to be such annoying jerks :/ So they decide to put the game on Kongregate a year or so after its release and now they give Ninjakiwi exclusive offers...
http://ninjakiwi.com/Games/Tower-Defense/Play/Bloons-Tower-Defense-5.html << On here you can clearly see the coop thing. I'm guessing that it is currently only for ninjakiwi but they updated the game news for every site it is on :(