The Trilogy

The classic progression from beginner to master. Hone in your addition and pattern recognition skills as you advance from 4x4 to 5x5 to 6x6 puzzle grids. Each step in grid size naturally increases the difficulty of solving and within each book the difficulty increases as you progress, creating a steady uphill climb through the trilogy.

Want more of this progression? Check out the original Frequency, which features 100 puzzles ranging from very very easy to very very difficult!