Mini-Sudoku: Each mini board is a 3×3 grid that must contain digits 1–9 (a complete permutation).
Supercell Value: The center cell of each mini board represents that cell’s value in the overall puzzle.
Overall Puzzle: The overall board is a 9×9 Sudoku with thick borders delineating each 3×3 block.
Interdependency: Some overall cells are preset. For empty overall cells, solve the mini puzzle to determine the digit; when you type it in, the overall board updates.