Let's hope you're really good with adding things up. In "Hundreds," by Semi Secret Software, your goal is to grow at least 100 points between circles that appear in each puzzle. It sounds simple enough, but the longer the numbers stay on the screen, the more they grow and change color. If they collide — well, that's it. For those looking to pump up their math skills — or just take on a challenging puzzle game — this will certainly add up for you.