This is an example of a 12x12 Sudoku. They are very similar to normal 9x9 Sudoku puzzles and you can
apply all of the same techniques. A standard 9x9 Sudoku will use the numbers 1 to 9, a 12x12 Sudoku
will also use the letters A, B and C.

Each row, column, and 3x4 region must contain 1-9, A, B, C once and only once. The letters can be
treated in exactly the same way as the numbers, we're only using letters because we ran out of numbers!

Look at the highlighted square. The 2s that are already in the grid stop a '2' being anywhere
else apart from the highlighted square. The highlighted square must be a '2'!

Look at the three highlighted cells in this puzzle, you can work out directly what they all are without
needing to fill in any more of the puzzle.

Have a try now!