I absolutely hate when developers make the only way to ascertain things by buying them. I have no qualms with them having a purchase 2x xp unavailable to those who don't pay, but all other things should be available even if you need like 50-100 wins to buy even one thing.
Btw if anyone is seriously trying to beat level 12, just zoom in on the screen where the boxes are so close. It took me 2 or 3 tries of doing this to pass that.
It ends after I think? level fourteen. If not its level 15. I am not beating it again to find out. You get a white you "win screen" with a large restart game button.
Was level 21 that hard o.0.... I mean yah it was a challenge but I got it in one try. I took out all on the right side and got any going up or below and worked my way around till they were all gone.....
Challenge 6 was the first i beat it only took me 2 tries... I quit normal after level 4 cause it bored me -.-....Btw challenges need something to tell you which ones you have done and havent.