The full logical solve of the hard Shikaku for September 8 to September 14, 2026, 15 × 15. 37 steps, 4 techniques, no guessing. Step through it, or jump to any step below.
The 9 in row 15, column 1 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.
The 3 in row 15, column 13 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.
Only the 8 in row 4, column 10 can reach row 5, column 8, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 2 in row 11, column 1 can reach row 12, column 1, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 7 in row 11, column 7 can reach row 11, column 2, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 2 in row 12, column 3 can reach row 12, column 2, so its rectangle must cover that cell. Just one of its rectangles does.
Every rectangle the 10 in row 3, column 15 could take covers the same 3 cells. Other numbers can’t use them, and that leaves the 8 in row 6, column 12 with one rectangle.
Only the 4 in row 3, column 9 can reach row 3, column 11, so its rectangle must cover that cell. Just one of its rectangles does.
Some cells can be reached by only one number. Each such number keeps only the rectangles that cover them, and after a few of these steps the 6 in row 12, column 8 has one rectangle left.
Only the 8 in row 15, column 5 can reach row 12, column 4, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 6 in row 15, column 8 can reach row 14, column 6, so its rectangle must cover that cell. Just one of its rectangles does.
Every rectangle the 6 in row 11, column 11 could take covers the same 2 cells. Other numbers can’t use them, and that leaves the 9 in row 13, column 11 with one rectangle.
The 2 in row 15, column 12 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.
Only the 6 in row 11, column 11 can reach row 11, column 9, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 11, column 12 can reach row 13, column 12, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 14, column 13 can reach row 14, column 14, so its rectangle must cover that cell. Just one of its rectangles does.
Working through which numbers reach each cell, and the cells every option of a number shares, the 2 in row 7, column 12 is left with one rectangle.
Working through which numbers reach each cell, and the cells every option of a number shares, the 4 in row 8, column 3 is left with one rectangle.
Working through which numbers reach each cell, and the cells every option of a number shares, the 9 in row 12, column 15 is left with one rectangle.
Try each rectangle the 10 in row 1, column 3 could still take. All but one lead to a contradiction, so it takes the one left.
Only the 10 in row 4, column 1 can reach row 1, column 1, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 8 in row 2, column 10 can reach row 1, column 8, so its rectangle must cover that cell. Just one of its rectangles does.
The 8 in row 2, column 13 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.
The 10 in row 3, column 15 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.
Only the 8 in row 7, column 3 can reach row 6, column 1, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 3, column 3 can reach row 4, column 3, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 3, column 6 can reach row 3, column 4, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 4, column 7 can reach row 3, column 7, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 6 in row 4, column 6 can reach row 4, column 4, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 7, column 5 can reach row 6, column 5, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 9 in row 8, column 6 can reach row 6, column 6, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 3 in row 7, column 9 can reach row 6, column 9, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 4 in row 6, column 11 can reach row 6, column 10, so its rectangle must cover that cell. Just one of its rectangles does.
Only the 6 in row 8, column 14 can reach row 8, column 10, so its rectangle must cover that cell. Just one of its rectangles does.
Try each rectangle the 8 in row 9, column 3 could still take. All but one lead to a contradiction, so it takes the one left.
Only the 12 in row 10, column 10 can reach row 10, column 5, so its rectangle must cover that cell. Just one of its rectangles does.
The 10 in row 9, column 13 has only one rectangle left that fits: the right area, inside the grid, clear of other numbers and of the rectangles drawn so far.