I actually lost track of what day I was on, they started to blend together, though I did buy every gun and most upgrade...I never needed anything more then the guass though...and I couldnt' rescue any more survivors either which was teh only challenging part
I hate how when you start getting pretty high up almost every 'surprise' is a bomb blitz....nothing like falling 1km+ getting all the way back up there again and....surprise! You're right back where you were.
The only thing that makes 3 million hard to get is teh damn UFO's and spikes that come out of no where. Way too much luck involved in that for me. But other then that really fun game.