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.

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.

Fill the grid with the digits 1 to 9. Each row and each column has exactly one of each digit. Each 3x3 box contains 3 digits once, 3 digits twice and 3 digits missing.

Fill the grid with the digits 1 to 9. Each row and each column has exactly one of each digit. Each 3x3 box contains 3 digits once, 3 digits twice and 3 digits missing.

Fill the grid with the digits 1 to 9. Each row and each column has exactly one of each digit. Each red region must contain 1 pair of numbers. Each cyan region must contain 2 pairs of numbers. Each yellow region must contain 3 pairs of numbers.

Fill in both grids so that every row, every column, and every 3x3 box contains the digits 1 through 9.

Fill the grid with the digits 1 to 8. Lines in each marked line and in the marked 4x2 regions have exactly one of each digit.

Fill in the flattened cube so that each of the numbers 0–9 and each of the letters A–F exactly once in cells of same face, square colour, font colour or row of 16.