Ripple Effect & Sudoku by Nikoli
Like a hit TV show, sudoku just keeps generating hot new spin-offs—like Ripple Effect! The Ripple Effect diagram is divided into areas of different shapes and sizes called rooms. If a room contains two squares, they must be filled with the numbers 1 and 2. If there are three squares, it’s 1, 2, and 3, and so on. But the “ripple effect” rule dictates that any two 1s in the same row or column must have at least one square between them…any two 2s must have at least two squares between them…and so on. Sudoku fans will get the idea instantly—and will enjoy mastering this exciting new challenge.