I broke the game on level 7. It only lets you place one, but I found a magic moment when you can place another weight as it calculates. Normally it just ignores it, but I was just a little off, and the game knew it. So when I added the right amount of weight to make it perfect, the game froze.
I was playing that game yesterday.
http://www.crazymonkeygames.com/Mass-Attack.html
An addictive game takes longer to get boring.