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This is a place chosen to make available some ideas (on puzzles, patterns, etc)
that seemed unsuitable for posting in a Forum, but some people may find interesting.
For difficult puzzles, possible solutions will not be shown (only hints).
For other puzzles, the solution wil be hidden so that a serious attempt can be made
without direct access to a solution.
(hopefully this will make the puzzles more interesting for newcomers)
(useful to look up for the meaning of some unfamiliar concept)
I proposed the following Classic Sudoku puzzle, which is a sister of
a recently proposed puzzle (not in this site).
This puzzle is solvable in two steps with a nice opening move.
(found with Sudoku Architect)
,-----------------------------------------------------------------,
| 3689 2 3579 | 3589 356 5689 | 4579 1 34579 | 9
| 13689 36789 13579 | 13589 2356 4 | 2579 2357 23579 | 8
| 1349 349 13459 | 1359 7 1259 | 6 235 8 | 7
|---------------------+--------------------+----------------------|
| 5 478 247 | 147 9 167 | 3 2678 267 | 6
| 89 1 79 | 2 56 3 | 5789 4 5679 | 5
| 2349 3479 6 | 457 8 57 | 2579 257 1 | 4
|---------------------+--------------------+----------------------|
| 7 3469 8 | 359 1 259 | 245 2356 23456 | 3
| 12349 349 12349 | 6 2345 25789 | 124578 23578 23457 | 2
| 12346 5 1234 | 378 234 278 | 12478 9 23467 | 1
'-----------------------------------------------------------------'
a b c d e f g h i
Update 1 (Jan 27, 2026)
The hint is to look carefully into the three boxes on the left.
This puzzle has a lower rating than the previous Sudoku-X puzzle,
but it seemed more challenging (and more fun to solve).
(generated and displayed with Sudoku6Explainer)
This is the grid (to check after performing the basics)
,---------------------------------------,
| 12 123 35 | 6 1245 1245 |
| 125 4 6 | 13 125 1235 |
|-------------------+-------------------|
| 6 5 12 | 134 124 1234 |
| 34 123 124 | 5 6 12 |
|-------------------+-------------------|
| 145 6 145 | 2 3 145 |
| 1235 123 12345 | 14 145 6 |
'---------------------------------------'
Sudoku-X
Update 1 (Jan 25, 2026)
One good opening move is to take of an
existing remote pair that gives a bivalued cell.
,---------------------------------------,
| 12 123 35 | 6 1245 45 | 6
| 125 4 6 | 13 125 1235 | 5
|-------------------+-------------------|
| 6 5 12 | 134 124 1234 | 4
| 34 123 124 | 5 6 12 | 3
|-------------------+-------------------|
| 145 6 145 | 2 3 145 | 2
| 1235 123 12345 | 14 145 6 | 1
'---------------------------------------'
a b c d e f Sudoku-X
One possible second move involves fishing:
a complex fish !
Update 2 (Jan 26, 2026)
The remote pair (move 1) is on 12:
a6 = c4 - b3.c3 = f4 => -12 f6.
For move 2, the existing fish is on the digit 1
and it eliminates (1)a5, (1)a1. Then, we get
,---------------------------------------,
| 12 123 35 | 6 245 45 | 6
| 25 4 6 | 13 125 1235 | 5
|-------------------+-------------------|
| 6 5 12 | 134 124 1234 | 4
| 34 123 124 | 5 6 12 | 3
|-------------------+-------------------|
| 145 6 145 | 2 3 145 | 2
| 235 123 12345 | 14 145 6 | 1
'---------------------------------------'
a b c d e f Sudoku-X
How to proceed ?
Update 3 (Jan 27, 2026)
(5)c6 can be eliminated using a wing with transport.
For Sudoku-X puzzles, we always pay close attention
to both diagonals for potential moves. This observation
and one digit pattern in the grid helped finding that
wing. Then, we arrive at
,---------------------------,
| 12 12 3 | 6 4 5 | f
| 5 4 6 | 13 12 123 | e
|-------------+-------------|
| 6 5 12 | 34 12 34 | d
| 34 123 124 | 5 6 12 | c
|-------------+-------------|
| 14 6 5 | 2 3 14 | b
| 23 123 124 | 14 5 6 | a
'---------------------------'
a b c d e f
Now, there is at least a wing-way
to finish.
I propose the following pleasant Sudoku-X puzzle.
I have solved it (manually) in 4 steps.
(generated and displayed with Sudoku6Explainer)
,---------------------------------------,
| 123 1346 356 | 146 13456 2456 | 6
| 1345 1236 356 | 146 2456 13456 | 5
|-------------------+-------------------|
| 6 5 4 | 3 12 12 | 4
| 23 23 1 | 5 46 46 | 3
|-------------------+-------------------|
| 1345 46 2 | 146 136 13456 | 2
| 45 1346 356 | 2 13456 136 | 1
'---------------------------------------'
a b c d e f X
Update (Jan 14, 2026)
For move 1, there is a nice fish that gives 4 eliminations
and opens the road for other patterns to exist. After finding
the fish, one gets
,-----------------------------------------,
| 123 1346 356 | 146 1345 2456 | 6
| 1345 1236 356 | 146 2456 1345 | 5
|-------------------+---------------------|
| 6 5 4 | 3 12 12 | 4
| 23 23 1 | 5 46 46 | 3
|-------------------+---------------------|
| 1345 46 2 | 146 13 1345 | 2
| 45 1346 356 | 2 13456 136 | 1
'-----------------------------------------'
a b c d e f X
Now, two wings are available.
Update (Jan 25, 2026)
The easiest (more powerful here) wing to find
seems to be the XYZ-wing that eliminates (3)a2,
followed by the LCs (3)e2 = (3)f2, (3)e2=(3)e6
that eliminate (3)e1.f1 and (3)a6. Also, (6)b1
gets eliminated by (6)b5=(6)f1.
,-----------------------------------------,
| 12 1346 356 | 146 1345 2456 | 6
| 1345 1236 356 | 146 2456 1345 | 5
|-------------------+---------------------|
| 6 5 4 | 3 12 12 | 4
| 23 23 1 | 5 46 46 | 3
|-------------------+---------------------|
| 145 46 2 | 146 13 1345 | 2
| 45 134 356 | 2 1456 16 | 1
'-----------------------------------------'
a b c d e f X
The other wing is a W-wing with transport
(seen first, but after the solve, it was
noticed that it is unnecessary)
We are near the end. How to continue ?
Update (Jan 26, 2026)
Now there is an easy fish that eliminates
(3)a5, c5 and solves the puzzle with basics to
the end. The unused W-wing is
(6=4)e3 - (4)e1 = (4)a1.b1 - (4=6)b2 - (6)b5 = (6)f1 => -6 f3,e1.///
Created: February 12, 2024
Contact: sudo.jco.br@gmail.com