Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 7 and two chess knights. All knights defend at least one other.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 8 and a chess knight. All knights defend at least one other.

Fill in the grid the digits 1 through 3. The digits in the boxes must be either all equal or all different. Horizontally or vertically adjazent cells of different boxes must be different.

Fill in the grid the digits 1 through 3. The digits in the boxes must be either all equal or all different. Horizontally or vertically adjazent cells of different boxes must be different.

Fill in the grid the digits 1 through 3. The digits in the boxes must be either all equal or all different. Horizontally or vertically adjazent cells of different boxes must be different.

Fill the grid with the digits 1 to 6 and with stars. Each row, column and 3x3-box will have exactly one of each digit and three stars. If you rotate the grid 180 degrees, the stars will appear at the same location as they appeared without the rotation.

Fill in the grid so that every row, every column, and every 5x2 box contains the digits 1 through 5. Each row, column, and box contains each digit twice. Orthogonally adjazent cells must have different digits.

Fill in the grid so that every row, every column, and every 5x2 box contains the digits 1 through 5. Each row, column, and box contains each digit twice. Orthogonally adjazent cells must have different digits.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 3. Each row, column, and 3x3 box contains each digit three times. The red arrows indicate that the digit in that cell can't appear in the direction of the arrow.

Fill in the grid so that every every 3x3 box contains the digits 1 through 9. Moreover all 18 diagonals of 9 cells (marked in the coloured diagrams with the same color) contain the digits 1 through 9.

It is allowed that numbers in a row or in a column are equal.