Implementation
final List<Cell> level1 = [
Cell(index: 0, row: 0, col: 0, value: null),
Cell(index: 1, row: 0, col: 1, value: null),
Cell(index: 2, row: 0, col: 2, value: null),
Cell(index: 3, row: 0, col: 3, value: null),
Cell(index: 4, row: 0, col: 4, value: null),
Cell(index: 5, row: 0, col: 5, value: null),
Cell(index: 6, row: 0, col: 6, value: null),
Cell(index: 7, row: 1, col: 0, value: null),
Cell(index: 8, row: 1, col: 1, value: null),
Cell(index: 9, row: 1, col: 2, value: null),
Cell(index: 10, row: 1, col: 3, value: null),
Cell(index: 11, row: 1, col: 4, value: null),
Cell(index: 12, row: 1, col: 5, value: null),
Cell(index: 13, row: 1, col: 6, value: null),
Cell(index: 14, row: 2, col: 0, value: null),
Cell(index: 15, row: 2, col: 1, value: null),
Cell(index: 16, row: 2, col: 2, value: null),
Cell(index: 17, row: 2, col: 3, value: null),
Cell(index: 18, row: 2, col: 4, value: null),
Cell(index: 19, row: 2, col: 5, value: null),
Cell(index: 20, row: 2, col: 6, value: null),
Cell(index: 21, row: 3, col: 0, value: null),
Cell(index: 22, row: 3, col: 1, value: null),
Cell(index: 23, row: 3, col: 2, value: null),
Cell(index: 24, row: 3, col: 3, value: null),
Cell(index: 25, row: 3, col: 4, value: null),
Cell(index: 26, row: 3, col: 5, value: null),
Cell(index: 27, row: 3, col: 6, value: null),
Cell(index: 28, row: 4, col: 0, value: null),
Cell(index: 29, row: 4, col: 1, value: null),
Cell(index: 30, row: 4, col: 2, value: null),
Cell(index: 31, row: 4, col: 3, value: null),
Cell(index: 32, row: 4, col: 4, value: null),
Cell(index: 33, row: 4, col: 5, value: null),
Cell(index: 34, row: 4, col: 6, value: null),
Cell(index: 35, row: 5, col: 0, value: 2),
Cell(index: 36, row: 5, col: 1, value: 2),
Cell(index: 37, row: 5, col: 2, value: 5),
Cell(index: 38, row: 5, col: 3, value: 5),
Cell(index: 39, row: 5, col: 4, value: 6),
Cell(index: 40, row: 5, col: 5, value: 4),
Cell(index: 41, row: 5, col: 6, value: 3),
Cell(index: 42, row: 6, col: 0, value: 1),
Cell(index: 43, row: 6, col: 1, value: 9),
Cell(index: 44, row: 6, col: 2, value: 2),
Cell(index: 45, row: 6, col: 3, value: 8),
Cell(index: 46, row: 6, col: 4, value: 5),
Cell(index: 47, row: 6, col: 5, value: 5),
Cell(index: 48, row: 6, col: 6, value: 3),
Cell(index: 49, row: 7, col: 0, value: 7),
Cell(index: 50, row: 7, col: 1, value: 4),
Cell(index: 51, row: 7, col: 2, value: 6),
Cell(index: 52, row: 7, col: 3, value: 9),
Cell(index: 53, row: 7, col: 4, value: 2),
Cell(index: 54, row: 7, col: 5, value: 2),
Cell(index: 55, row: 7, col: 6, value: 1),
Cell(index: 56, row: 8, col: 0, value: 3),
Cell(index: 57, row: 8, col: 1, value: 9),
Cell(index: 58, row: 8, col: 2, value: 1),
Cell(index: 59, row: 8, col: 3, value: 8),
Cell(index: 60, row: 8, col: 4, value: 1),
Cell(index: 61, row: 8, col: 5, value: 2),
Cell(index: 62, row: 8, col: 6, value: 9),
];
