- 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.
- If absolute difference between two digits in neighbouring cells equals 1, then they are separated by a white dot. If the digit is a half of digit in the neighbouring cell, then they are separated by black dot. The dot between 1 and 2 can be either white or black.

- 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.
- If absolute difference between two digits in neighbouring cells equals 1, then they are separated by a white dot. If the digit is a half of digit in the neighbouring cell, then they are separated by black dot. The dot between 1 and 2 can be either white or black.

- 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 along each line are monotonically increasing or decreasing.

- Digits along each line are monotonically increasing or decreasing.

- Digits do not repeat along the marked diagonals.

- Digits do not repeat along the marked diagonals.

- 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.

- 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 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.

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

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

- Identical digits do not touch each other diagonally.

- Identical digits do not touch each other diagonally.

- 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.

- 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.

- 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.

- A number at the edge of the diagram indicates the difference between the highest and the lowest number in the first three cells in the corresponding row or column.

- A number at the edge of the diagram indicates the difference between the highest and the lowest number in the first three cells in the corresponding row or column.

- 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 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.

- 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.
- There are some dots between cells. The numbers on each side of a dot must always be consecutive. Not all possible dots are marked.

- 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.
- There are some dots between cells. The numbers on each side of a dot must always be consecutive. Not all possible dots are marked.

- A dot between two cells indicates that the result of at least one of the basic operations (addition, subtraction, multiplication, division) of the numbers in these two cells is 8. Is the dot missing, no one of the basic operations results in an 8.

- A dot between two cells indicates that the result of at least one of the basic operations (addition, subtraction, multiplication, division) of the numbers in these two cells is 8. Is the dot missing, no one of the basic operations results in an 8.

- 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 at the edge of the diagram indicates the difference between the highest and the lowest number in the first three cells in the corresponding row or column.

- 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.

- 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.