Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 7 and two chess knights. No knights attack each other.

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.

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 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 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 the grid with the digits 1 to 9. The digits represent the height of the skyscraper in each cell. Each row and column 3x3-box has exactly one of each digit. Each 3x3 box contains 3 digits once, 3 digits twice and 3 digits missing. The clues along the edges tell you how many skyscrapers you can see from that vantage point.