UP, DOWN, LEFT and RIGHT arrow keys (or W, A, S and D) navigate the current selected cell in the grid.

Hold CTRL or SHIFT to select multiple cells.

CTRL+A selects all cells in the grid.

1-9 will fill in an empty cell with that number.

Hold CTRL or SHIFT to mark or remove a hint for that number in the selected cells.

Backspace or Delete will clear out the selected cells.

CTRL+Z will undo the last change you made, including restoring any hints cleared out by placing a digit.

SUDOKU BASICS

Sudoku is a logic puzzle game. You are provided with a number of hints in a grid. Fill the rest of grid with the numbers 1 through 9, with the following restrictions:

• Each row must contain the numbers 1 through 9 with no duplicates.
• Each column must contain the numbers 1 through 9 with no duplicates.
• Each marked 3x3 box must contain the numbers 1 through 9 with no duplicates.

In the examples below, starting from the 1 near the center, all the yellow squares cannot contain a 1 by these rules.

CHESS CONSTRAINTS

Each puzzle is a standard Sudoku puzzle with the one or both of the following additional rules:

Knight

No number can have a matching number a "Knight's Move" away from itself. None of the lilac squares here could have a 1.

King

No number can have a matching number a "King's Move" away from itself. None of the teal squares here could have a 1.

Knight / King

No number can have a matching number a "Knight's Move" *OR* a "King's Move" away from itself. None of the lilac OR teal squares here could have a 1.