Train the brain while having fun at the same time. These puzzles go by order of complexity, from quick teasers to twisters, and up to bafflers, and they're all enjoyable to solve. The middle section, Tough Twisters, has some hints at the section for a little extra help. "Climb" a word ladder, converting the word PASSER into SPARSE by switching just two letters at a time. Figure out what's next in the following sequence of numbers: 17, 19, 23, and...