- 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.
- Adjacent cells with digits summing to 5 are marked by V, while those summing to 10 are marked by X. Not all possible V and X are marked.

- 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.
- Adjacent cells with digits summing to 5 are marked by V, while those summing to 10 are marked by X. Not all possible V and X are marked.

- 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.
- 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.

- Identical digits do not touch each other diagonally.

- Identical digits do not touch each other diagonally.

- Digits do not repeat along the marked diagonals.

- Digits do not repeat along the marked diagonals.

- 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.

- 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.

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

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

- Adjacent cells with digits summing to 5 are marked by V, while those summing to 10 are marked by X. Not all possible V and X are marked.

- Identical digits do not touch each other diagonally.

- Identical digits do not touch each other diagonally.

- 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.

- Digits along each line are monotonically increasing or decreasing.

- Digits along each line are monotonically increasing or decreasing.

- 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.

- Digits outside the grid indicate the sum of the first 3 digits in the corresponding direction.

- Digits outside the grid indicate the sum of the first 3 digits in the corresponding direction.

- A number between two cells indicates the product of the numbers in these cells. A number between four cells indicates the product between two diagonally adjacent cells, either top left + right bottom (\) or top right + bottom left (/).

- A number between two cells indicates the product of the numbers in these cells. A number between four cells indicates the product between two diagonally adjacent cells, either top left + right bottom (\) or top right + bottom left (/).

- A number between two cells indicates the difference of the numbers in these cells. A number between four cells indicates the difference between two diagonally adjacent cells, either top left + right bottom (\) or top right + bottom left (/). If one of the characters < or > is specified the apex of the angle points to the smaller of these numbers.

- A number between two cells indicates the difference of the numbers in these cells. A number between four cells indicates the difference between two diagonally adjacent cells, either top left + right bottom (\) or top right + bottom left (/). If one of the characters < or > is specified the apex of the angle points to the smaller of these numbers.

- Numbers in the red circle are not allowed appears in four squares which is nearby the intersection of row and column red circles.

- Numbers in the red circle are not allowed appears in four squares which is nearby the intersection of row and column red circles.

- 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.

- 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.

- 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.

- A dot between two cells indicates that the sum of the numbers in these cells is 10 or 11. If no dot between two cells the sum of the numbers in these cells must not be 10 or 11.

- A dot between two cells indicates that the sum of the numbers in these cells is 10 or 11. If no dot between two cells the sum of the numbers in these cells must not be 10 or 11.