Center Dot Sudoku

Center Dot Sudoku is a logical puzzle. This Sudoku variant contains one additional, 10th block composed of 9 centre cells.

Rules: In each cell of the 9×9 grid, enter a number in the range 1–9. Each number must appear exactly once in each row, column, and block.
Additional rules: The center cells of the nine blocks form an additional 10th block. The numbers in this block can only appear once.