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Sudoku Islands are based on a regular 9x9 grid with four additional shaded areas dropped on top. Each of these shaded areas will have each digit, 1-9, appear in them exactly once.


With a single Trividoku puzzle, you have nine spaces in the grid labeled “A” through “I”. Below the grid you have a left side also labeled “A” – “I” and a numbered right side, “1” – “9”. Each item on the left will uniquely match a single thing on the right. When you discover a pair that matches, for example if “C” and “3” match then you can write in a “3” in the space on the grid with a “C”.


In a Stars & Stripes Sudoku puzzle each row, column and 3x4 box contains the digits 1-9 as well as three stars. 

Sudoku Earthquake starts with a regular 9x9 Sudoku grid with a “fault line” running from one side of the puzzle to another. At the bottom of the puzzle the digits that will appear on that fault line are shown. A fault is rarely nine digits long so the digits on the fault may be repeated or a digit may not even appear at all.