Welcome!
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)
(Guidelines for using this site here)
(useful to look up for the meaning of some unfamiliar concept)
I propose the following tough Classic Sudoku puzzle.
(found with Sudoku Explainer)
After basics
,-------------------------------------------------------,
9 | 9 34 2 | 8 135 6 | 15 145 7 |
8 | 368 1 467 | 579 359 357 | 5689 4589 2 |
7 | 5 78 67 | 179 2 4 | 1689 189 3 |
|-----------------+-----------------+-------------------|
6 | 7 2469 469 | 3 156 125 | 12589 1589 1459 |
5 | 236 2346 5 | 126 8 9 | 123 7 14 |
4 | 1 239 8 | 257 4 257 | 2359 6 59 |
|-----------------+-----------------+-------------------|
3 | 68 78 1679 | 4 1359 135 | 159 2 1569 |
2 | 26 269 169 | 159 7 8 | 4 3 1569 |
1 | 4 5 3 | 1269 169 12 | 7 19 8 |
'-------------------------------------------------------'
a b c d e f g h i Classic Sudoku
I propose the following (tough) Slitherlink puzzle.
(Source: Simon Tatham's Collection)
.---------------------------------------.
| . . . . . . . . . . |
9 | 3 2 3 1 1 2 |
| . . . . . . . . . . |
8 | 2 2 3 |
| . . . . . . . . . . |
7 | 2 1 |
| . . . . . . . . . . |
6 | 3 3 1 |
| . . . . . . . . . . |
5 | 1 2 2 |
| . . . . . . . . . . |
4 | 2 3 3 2 1 |
| . . . . . . . . . . |
3 | 3 3 2 2 |
| . . . . . . . . . . |
2 | 2 1 3 1 3 |
| . . . . . . . . . . |
1 | 1 3 |
| . . . . . . . . . . |
'---------------------------------------'
a b c d e f g h i Slitherlink
I propose the following Sudoku-X puzzle to be solved manually.
(generated and displayed with Sudoku6Explainer)
+-------+-------+
| . . . | . . . |
| . . . | 5 . . |
+-------+-------+
| . . . | . 1 2 |
| 1 6 . | . . . |
+-------+-------+
| . . 4 | . . . |
| . . . | . . . |
+-------+-------+ Sudoku-X
Update 1 (Oct 23, 2026)
After basics we get
,---------------------------------------,
6 | 346 345 356 | 123 236 134 |
5 | 2346 1234 136 | 5 34 36 |
|-------------------+-------------------|
4 | 345 345 35 | 6 1 2 |
3 | 1 6 2 | 34 345 345 |
|-------------------+-------------------|
2 | 236 135 4 | 123 2356 356 |
1 | 35 23 136 | 1234 23456 1356 |
'---------------------------------------' Sudoku-X
a b c d e f
This puzzle can be solved in one step.
Update 2 (Oct 24, 2026)
,---------------------------------------,
6 | 346 345 356 | 123 236 134 |
5 | 234-6 1234 136 | 5 34 36 |
|-------------------+-------------------|
4 | 345 345 35 | 6 1 2 |
3 | 1 6 2 | 34 345 345 |
|-------------------+-------------------|
2 | 236 135 4 | 123 2356 356 |
1 | 35 23 136 | 1234 23456 1356 |
'---------------------------------------' Sudoku-X
a b c d e f
Using the diagonal we can show that (6)a5, (6) f2
both false. This move creates the strong link
(6)a2 = (6)a6, that eliminates (6)e2 and solves
the puzzle.
Created: February 12, 2024
Contact: sudo.jco.br@gmail.com