Sudoku X;Each puzzle consists of a 9x9 grid containing given clues in various places. The object is to fill all empty squares so that the numbers 1 to 9 appear exactly once in each row, column, diagonal and 3x3 box. Killer Sudoku;Killer Sudoku is a mix of Sudoku and Kakuro. Your goal is the same as in regular sudoku: fill every row, column and 3x3 region with the numbers 1-9 once. The difference is how you arrive at those numbers. The objective is to fill the grid with numbers from 1 to 9 in a way that the following conditions are met: Each row, column, and nonet contains each number exactly once. The sum of all numbers in a cage must match the small number printed in its corner. No number appears more than once in a cage. (This is the standard rule for killer sudoku, and implies that no cage can include more than 9 cells.) Jigsaw Sudoku;The rules of Jigsaw Sudoku are similar to standard Sudoku, since you must place each of the numbers 1 to 9 (or 1 to whatever the size of the puzzle is) into each of the rows and columns. However whereas standard Sudoku also has rectangular boxes that must each contain every number, in Jigsaw Sudoku these boxes are replaced by different bold-lined shapes that must each contain every number instead. Kropki Sudoku;Kropki Sudoku puzzles add black (o) and white (o) circles to a regular Sudoku puzzle. All pairs of touching squares which contain consecutive values (such as 2 & 3 or 6 & 7) are marked with a white circle: o. Also, all pairs of touching squares which contain values where one number is exactly twice the value of the other (such as 2 & 4, or 4 & 8) are marked with a black circle: o. This applies to left/right, up/down touching only - there are no diagonal markers. All possible o and o are given, so if there is no circle between two touching squares then they are not consecutive and one is not double the value of the other.