Click on a square and type the number you want to fill in the square. Like regular Sudoku, you use the numbers 1-9 in the 3x3 boxes on the grid. Each number can only appear once in a box, but can't be repeated in the same row or column.

There's a new challenge, and it involves some math! In the upper left corner, some squares will have a number and a group of boxes around it are the same color. As you fill in the squares, you have to make sure your answers add up to the corner number.

If the number you type in is red, that means the number doesn't belong in that spot. If the number is black, that means you put it in the right place!

HINT: If you're stuck, click the lightbulb and you can reveal the answer to a certain square (or reveal the entire puzzle!)