- 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.
- The number in a cell with an arrow must not be repeated in a cell the arrow points to.

- 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.
- The number in a cell with an arrow must not be repeated in a cell the arrow points to.

- 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.
- In all cases where two digits have a consecutive value or one digit is two times as big as the other digit (or both), a greater than sign is placed. Digits have to be placed in accordance with the sign.

- In all cases where two digits have a consecutive value or one digit is two times as big as the other digit (or both), a greater than sign is placed. Digits have to be placed in accordance with the sign.

- 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.

- In all cases where two digits have a consecutive value or one digit is two times as big as the other digit (or both), a greater than sign is placed. Digits have to be placed in accordance with the sign.

- Digits do not repeat along the marked diagonals.

- Digits do not repeat along the marked diagonals.

- Identical digits do not touch each other diagonally.

- Identical digits do not touch each other diagonally.

- Cells with circles must contain digits 1-2-3, cells with squares must contain digits 4-5-6, blank cells must contains digits 7-8-9.

- Cells with circles must contain digits 1-2-3, cells with squares must contain digits 4-5-6, blank cells must contains digits 7-8-9.

- 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.

- 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.

- The diagram is a toroid; some of the 3×3 regions don't end at the right (lower) edge of the diagram but continue at the left (upper) edge of the diagram.

- The diagram is a toroid; some of the 3×3 regions don't end at the right (lower) edge of the diagram but continue at the left (upper) edge of the diagram.

- 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.

- 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.

- 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.

- The arrows outside the grid indicate that the nearest three digits in the corresponding direction are in ascending or descending order (the highest number is always in the direction of the arrow). All possible arrows are given, so if there is no arrow, the first three digits do not form an increasing sequence in either direction.

- The arrows outside the grid indicate that the nearest three digits in the corresponding direction are in ascending or descending order (the highest number is always in the direction of the arrow). All possible arrows are given, so if there is no arrow, the first three digits do not form an increasing sequence in either direction.

- Adjacent cells with digits summing to 5 are marked by V, while those summing to 10 are marked by X. All possible V and X are marked.

- Adjacent cells with digits summing to 5 are marked by V, while those summing to 10 are marked by X. All possible V and X are marked.

- One of the numbers in the four cells around a dot is the num of the other three numbers.

- One of the numbers in the four cells around a dot is the num of the other three numbers.

- Cells with circles must contain digits 1-2-3, cells with squares must contain digits 4-5-6, blank cells must contains digits 7-8-9.

- The sum of the digits along the path of each arrow equals the digit in the circled cell. Digits may repeat within an arrow shape.

- The sum of the digits along the path of each arrow equals the digit in the circled cell. Digits may repeat within an arrow shape.

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

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