1000 PLAYTHINKS is the most compulsive， head-scratching， and-at 5.08 pounds-gargantuan puzzle book ever. An obsessive collection of 1，000 challenges， puzzles， riddles， illusions-both original as well as must-do classics. Jam-packed on the page and illustrated throughout in full-color， with a visual for each entry， the book， opened anywhere， is like a call to action. And once started it s hard to stop， because at the end of every successfully completed game the puzzle-solver feels smart， successful， and at one with the beauty of mathematics. Created by Ivan Moscovich， PLAYTHINKS is the first and only book where science， math， and art puzzles all come together. Broken down by chapter， PLAYTHINKS challenges with 12 basic categories， including games of Geometry; Patterns; Numbers; Logic and Probability; and Perception. A special Bonus Round is included for die-hard puzzlers who， after all that， still haven t had enough. An easy-to-read key at the top of each game ranks its difficulty on a scale of 1 to 10. The lie-flat spiral binding makes the hefty book completely reader-friendly. So do the answers in the back.