Symmetric Unequal Sudoku (Fun With Sudoku #80)

Welcome to a puzzle that adds a symmetric twist to your Sudoku solving! This Symmetric Unequal Sudoku is a unique variant that I created, and it's now the 80th puzzle in our Fun With Sudoku Series. The puzzle uses a classic 9x9 grid, but with an additional constraint: 40 pairs of cells are symmetric according to a 180° rotation of the grid. The rule is that the two digits in any such symmetric pair must be different. Think of it as using the two main diagonals as mirrors, where a cell and its mirror image must not contain the same digit.

Interestingly, this puzzle was designed as a variant, but it's so well-constructed that expert solvers can solve it using only the classic Sudoku rules! This makes it a great puzzle for solvers of all levels—whether you use the symmetric rule as a guide or challenge yourself to solve it purely as a classic Sudoku.

Rules of the Symmetric Unequal Sudoku

Classic Sudoku Rules apply. Additionally, there are 40 pairs of cells symmetric according to a 180° rotation. The two digits in the two cells should be different.

To understand rules more clearly, consider two main diagonals as mirrors. Digits in a particular cell and its mirror image should be different.