This is a fantastic puzzle to give your brain a good workout. No instructions, no anything. You figure out everything for yourself. I got stuck on level 42, but I kept trying and finally finished all 50 levels. After a break from it for awhile, I’ve started over. It kind of seems like it has started with s new set of combinations, but I can’t be sure. Anyway, no pressure, no timers, no distractions. It’s great. It’s challenging enough to give anyone’s mind a real workout— without the stress!!