dude, whenever I build a good sized tower, a random 'Gust of wind' comes along and pushes it over WTF? it was a perfectly fine tower until it randomly toppled over!
if you dont know how to get the butterfingers achievment, get 1000 mistakes in one song. you'll hear a voice say butterfingers once you get to 1000 and the mistake counter will say a simple word 'lots' lololz
seriously, when you start fighting more than 1 enemy at a time, the game starts getting really difficult because there are far too many lasers/bombs/round laser thingys to dodge!