Logic Masters Deutschland e.V.

Rules:

• Normal sudoku rules apply.
• The grid is mostly covered in fog; placing a correct digit removes fog in the neighboring and surrounding cells.
• A red "X" indicates a product square: a 2x2 region of cells where the product of the digits on the negative diagonal equals the product of the digits on the positive diagonal.
• A blue "X" indicates a sum square: a 2x2 region of cells where the sum of the digits on the negative diagonal equals the sum of the digits on the positive diagonal.
• Digits in cells separated by a white dot must be consecutive.
• No rule is subject to a negative constraint.