I always play puzzle games instead of doing my homework; I feel I'm expanding my mind in a more useful way.
Puzznic is one of those 'ow, my brain hurts' games. You move matching and non-matching blocks around, trying to put similar ones next to each other. If you don't understand, tough. I'm not explaining it again. Let me say, though, that it's got nearly 100 levels, it's tricky, there's a dangerous time-limit and it's frustrating. I loved it. You know how when you play some games, you forget about everything else in your life? Well, that happened to me when I was playing Puzznic. I almost forgot what a financially-astute, pennywise genius I am. Amazing, eh?
So if you want a puzzle game, I'm afraid it's time to bite the bullet and give £3.99 to the person behind the counter at your local shop. You won't regret it - well, not much (although £3.99 is not such an inconsiderate sum for a game like this).