- Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each of the rows, columns and the nine outlined 3x3 regions.
- Digits have to be place in accordance with the “greater than” signs.

- Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each of the rows, columns and the nine outlined 3x3 regions.
- Digits have to be place in accordance with the “greater than” signs.

- Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each of the rows, columns and the nine outlined 3x3 regions.
- Everywhere 2 odd and 2 even digits form a 2x2 checkerboard pattern, a Battenburg marking is given. A checkerboard pattern is a 2x2 area of cells where the top-left and bottom-right cells are of one type and the top-right and bottom-left cells are of another type. All possible dots are marked.

- Everywhere 2 odd and 2 even digits form a 2x2 checkerboard pattern, a Battenburg marking is given. A checkerboard pattern is a 2x2 area of cells where the top-left and bottom-right cells are of one type and the top-right and bottom-left cells are of another type. All possible dots are marked.

- Sujiken (from Japanese "sujikai", literally "diagonal") is a variation of Sudoku . The puzzle consists of a triangular grid of cells containing digits from 1 to 9. The objective is to fill a grid with digits so that each cell contains a digit and no digit is repeated in any column, row and diagonal in any direction. Also, no digit occurs twice in any of the three larger 3 x 3 square regions and any of the three larger triangular regions enclosed by thick borders.

- Sujiken (from Japanese "sujikai", literally "diagonal") is a variation of Sudoku . The puzzle consists of a triangular grid of cells containing digits from 1 to 9. The objective is to fill a grid with digits so that each cell contains a digit and no digit is repeated in any column, row and diagonal in any direction. Also, no digit occurs twice in any of the three larger 3 x 3 square regions and any of the three larger triangular regions enclosed by thick borders.

- Some thermometer shapes are placed in the grid. Digits are strictly increasing from the round bulb of the thermometer to each flat end.

- Some thermometer shapes are placed in the grid. Digits are strictly increasing from the round bulb of the thermometer to each flat end.

- Each number outside the grid is the sum of the first X numbers placed in the corresponding direction, where X is equal to the first number placed in that direction.

- Each number outside the grid is the sum of the first X numbers placed in the corresponding direction, where X is equal to the first number placed in that direction.

- Some intersections of the grid lines are marked by a number and an operator (+, -, x, /) in a circle. The number is the result of the operation, applied to both pairs of diagonally opposite cells. An E in the circle indicates that all four adjacent digits are even, while an O indicates that all four adjacent digits are odd.

- Some intersections of the grid lines are marked by a number and an operator (+, -, x, /) in a circle. The number is the result of the operation, applied to both pairs of diagonally opposite cells. An E in the circle indicates that all four adjacent digits are even, while an O indicates that all four adjacent digits are odd.

- Numbers with arrows indicate sum of the numbers in each direction.

- Numbers with arrows indicate sum of the numbers in each direction.

- A number at the edge of the diagram indicates the difference between the first and the last number in the corresponding row or column.

- A number at the edge of the diagram indicates the difference between the first and the last number in the corresponding row or column.

- The connected shaded cells contain each digit from 1 to 9.

- The connected shaded cells contain each digit from 1 to 9.

- Each number outside the grid is the sum of the first X numbers placed in the corresponding direction, where X is equal to the first number placed in that direction.
- Digits have to be place in accordance with the “greater than” signs.

- Digits have to be place in accordance with the “greater than” signs.

- Some thermometer shapes are placed in the grid. Digits are strictly increasing from the round bulb of the thermometer to each flat end.

- Arrows and numbers outside gridding means how many different numbers in corresponding direction grid.

- Arrows and numbers outside gridding means how many different numbers in corresponding direction grid.

- A number in a squared cell indicates how many different numbers the four diagonally adjacent cells contain. A number in a circled cell indicates how many different numbers the eight orthogonally and diagonally adjacent cells contain.

- A number in a squared cell indicates how many different numbers the four diagonally adjacent cells contain. A number in a circled cell indicates how many different numbers the eight orthogonally and diagonally adjacent cells contain.

- Everywhere 2 odd and 2 even digits form a 2x2 checkerboard pattern, a Battenburg marking is given. A checkerboard pattern is a 2x2 area of cells where the top-left and bottom-right cells are of one type and the top-right and bottom-left cells are of another type. All possible dots are marked.

- The digits in two orthogonally adjacent cells cannot have a sum of either 5 or 10.

- The digits in two orthogonally adjacent cells cannot have a sum of either 5 or 10.

- Digits in adjacent cells cannot be consecutive.

- Digits in adjacent cells cannot be consecutive.

- Each number at the intersection of four cells is the sum of digits in those four cells.

- Each number at the intersection of four cells is the sum of digits in those four cells.

- Grey cells in the grid represent many cloned areas. Digits in these areas on corresponding positions must be identical. Cloned areas are only moved, without rotation or reflection.

- Grey cells in the grid represent many cloned areas. Digits in these areas on corresponding positions must be identical. Cloned areas are only moved, without rotation or reflection.

- If a shaded cell and a white cell are adjacent then the digit in the shaded cell is greater.

- If a shaded cell and a white cell are adjacent then the digit in the shaded cell is greater.

- There are some dots between cells. The numbers on each side of a dot must always be consecutive. All possible dots are marked.

- There are some dots between cells. The numbers on each side of a dot must always be consecutive. All possible dots are marked.