in Volume 2: Level 2: Building Core Strength, the brain puzzles are more challenging than the beginner exercises of Volume 1, but they are not at the intermediate level of Volume 3 or the advanced level of Volume 4. The Level 2 exercises are designed to build on the momentum of the introductory Level 1 exercises, adding puzzles that will continue to develop and enhance basic right brain/left brain skills (though it is not necessary to complete Volume 1 in order to do Volume 2 each book stands on its own). The processing speed puzzles in Volume 2 will help readers concentrate on "building core strength" that will enhance mental agility. While the puzzles in Level 2 are still fairly easy and won't be daunting to most beginners, they provide a higher level of mental stretch than Level 1. The other volumes in this series include Level 3: increasing Stamina (puzzles at an intermediate level of difficulty) and Level 4: Accelerating the Pace (puzzles that are at an advanced level to challenge and stimulate brain activity), both are available in spring 2013.