I should never have looked up logic puzzles on the internet!! As I said in a previous post, I love them, but now I can spend time on the internet playing yet another game. One annoying thing about them is that, if you click away from the grid, you can lose the grid and have to start all over again. Very annoying.
Another couple of games that I love are Gridshock and Qrossfire. I can spend quite a bit of time on them too. I try to remember my OH&S for computers but the time just disappears and I find that I have sat still for a while and can get stiff.