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).
This Hidoku puzzle was created after great modifications from a previous version
with (designed) complex solving path. The modifications were made to circunvent
non-uniqueness issues at the end of the solving path. The resulting puzzle is easier
to solve than I intended, but hopefully it is a good enough challenge.
Oops! (forgot to include ascii grid! Done below)
,--------------------------------,
| __ __ __ __ __ __ __ 18 | 8
| __ __ 58 24 __ 21 17 __ | 7
| __ __ __ __ 25 __ 15 __ | 6
| __ 37 29 __ 64 10 __ __ | 5
| __ __ __ __ __ __ 53 __ | 4
| __ 40 62 __ __ 48 __ 52 | 3
| __ 42 __ 02 __ __ __ __ | 2
| __ __ 01 __ __ 04 __ 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
Update (Dec 28, 2025)
We have easy moves at the start:
1.(49)g2 2.(51)h2 3.(05)g1! 4.(06)f2
5.(03)e1! 6.(63)d4
,--------------------------------,
| __ __ __ __ __ __ __ 18 | 8
| __ __ 58 24 __ 21 17 __ | 7
| __ __ __ __ 25 __ 15 __ | 6
| __ 37 29 __ 64 10 __ __ | 5
| __ __ __ *63 __ __ 53 __ | 4
| __ 40 62 __ __ 48 __ 52 | 3
| __ 42 __ 02 __ *06 *49 *51 | 2
| __ __ 01 __ *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
How to continue ?
Update (Dec 29, 2025)
57
,--------------------------------,
| __ __ __ __ __ __ __ 18 | 8
| __ __ 58 24 __ 21 17 __ | 7
| __ __ __ __ 25 __ 15 __ | 6
| __ 37 29 __ 64 10 __ __ | 5
| __ __ __ *63 __ __ 53 __ | 4
| __ 40 62 __ __ 48 __ 52 | 3
| __ 42 __ 02 __ *06 *49 *51 | 2
| __ __ 01 __ *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
7.(54)f4 8.(55)e4 9.(56)d5 forces the
path 06 -> 10 to go through cells g3,h4,g5.
That makes the path from 10 to 15 impossible!
So,
7.(54)g5!! 8.(55)f6 9.(56)e7
57
,--------------------------------,
| __ __ __ __ __ __ __ 18 | 8
| __ __ 58 24 *56 21 17 __ | 7
| __ __ __ __ 25 *55 15 __ | 6
| __ 37 29 __ 64 10 *54 __ | 5
| __ __ __ *63 __ __ 53 __ | 4
| __ 40 62 __ __ 48 __ 52 | 3
| __ 42 __ 02 __ *06 *49 *51 | 2
| __ __ 01 __ *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
What is the right place for 57 ? How to continue ?
Update (Dec 30, 2025)
If 10.(57)d6, then 11. (26)d5 and the path from
26 to 29 gets in the way of the path from 58 to 62.
So,
10.(57)d8!!
,--------------------------------,
| __ __ __ *57 __ __ __ 18 | 8
| __ __ 58 24 *56 21 17 __ | 7
| __ __ __ __ 25 *55 15 __ | 6 . 59
| __ 37 29 __ 64 10 *54 __ | 5 . 60
| __ __ __ *63 __ __ 53 __ | 4 . 09, 61
| __ 40 62 __ __ 48 __ 52 | 3
| __ 42 __ 02 __ *06 *49 *51 | 2
| __ __ 01 __ *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
Now 10 placements are available and
we reach easily
46 47
26 07
,--------------------------------,
| __ __ __ *57 *23 *22 *20 18 | 8
| __ __ 58 24 *56 21 17 *19 | 7
| __ __ __ __ 25 *55 15 *16 | 6 . 59
| __ 37 29 __ 64 10 *54 *14 | 5 . 60
| __ __ __ *63 *09 *11 53 *13 | 4 . 61
| __ 40 62 __ __ 48 *12 52 | 3 . 08
| __ 42 __ 02 __ *06 *49 *51 | 2
| __ __ 01 __ *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
How to make progress now ?
Update (Dec 31, 2025)
07,47 are locked into e2,e3 and 08 must go
into one of the cells e2,e3,d3, so
21.(08)d3! 22.(47)e2! 23.(07)e3 and five
more placements lead to
26
,--------------------------------,
| __ __ __ *57 *23 *22 *20 18 | 8
| __ __ 58 24 *56 21 17 *19 | 7
| __ __ __ __ 25 *55 15 *16 | 6 . 59
| __ 37 29 __ 64 10 *54 *14 | 5 . 60
| __ __ __ *63 *09 *11 53 *13 | 4 . 61
| __ 40 62 *08 *07 48 *12 52 | 3
|*41 42 *45 02 *47 *06 *49 *51 | 2
|*43 *44 01 *46 *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
How to continue ?
Update (Jan 02, 2026)
29.(59)b6!!
[using the route through d5,c4 to connect
58 to 62 gets in the way of the path from
25 to 29, in particular, there is no place for 27]
after two more placements we get
26
,--------------------------------,
| __ __ __ *57 *23 *22 *20 18 | 8
| __ __ 58 24 *56 21 17 *19 | 7
| __ *59 __ __ 25 *55 15 *16 | 6
|*60 37 29 __ 64 10 *54 *14 | 5
| __ *61 __ *63 *09 *11 53 *13 | 4
| __ 40 62 *08 *07 48 *12 52 | 3
|*41 42 *45 02 *47 *06 *49 *51 | 2
|*43 *44 01 *46 *03 04 *05 50 | 1
'--------------------------------'
a b c d e f g h JCO#8
and from here the fact that 26,27,28,29
are locked into the region c4,c6,d5,d6
solves the puzzle with singles.
This new Hidoku puzzle is quite different from HP#8: the difficulties
in the puzzle are present only at the start. After something is
noticed (proved), the solution is smooth to the end.
,-----------------------------,
| __ __ __ __ __ __ __ | 7
| __ __ 22 __ 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 __ __ __ __ __ | 4
| __ __ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
Updated (Dec 28, 2025)
The natural place to start is to find the
right spot for the number 44 (2 possibilities).
One must show that (44)d4 is false. After that
and an observation that comes for free from the
analysis, the remaning 37 moves are easily found.
Update (Dec 30, 2025)
Part 1 [of analysis]:
We consider the possibility of 1. (44)d4
46 47 48
,-----------------------------,
| __ __ __ __ __ __ __ | 7
| __ __ 22 __ 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 __ 44? __ __ __ | 4
| __ __ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
Part 1.1:
within the possibility of 1.(44)d4,
we consider the possibility of 2.(47)e7 3.(46)d6.
48
,-----------------------------,
| __ __ __ __ 47? __ __ | 7
| __ __ 22 46? 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 __ 44? __ __ __ | 4
| __ __ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
We want to see if this configuration
leads to a contradiction in order
to discard this possibility of 2.(47)e7.
How can we show this ?
Update (Dec 31, 2025)
The analysis for this possibility will be shown
next. Similar analysis for the other two
possibilities (1.(44)d4 2.(47)e5 3.(46)d5/d6 is
the second possibility and 1.(44)d4 2.(47)e4 3.(46)d5
is the third possibility) will be omitted because it
contains similar ideas.
Analysis for the first possibility:
If we connect 08 -> 19 using cells c4,d5,
then 19 -> 22 must use cells c7,d7. Now,
22 -> 26 and 26->31 must use cells b6,b7,
a7,a6,a5,a4, and a3|b3. Then a3|b3 must
be used for the path 01 -> 08, but this
path gets in the way of the path 31 -> 34.
(here | denotes "or")
,-----------------------------,
| zz zz yy yy 47? __ __ | 7
| zz zz 22 46? 19 __ 49 | 6
| zz 26 45 xx __ __ __ | 5
| zz 08 xx 44? __ __ __ | 4
| z_ z_ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
After all three possibilites are discarded
as leading to impossible situations, we
finally have a first move!
1.(44)c4!!
,-----------------------------,
| __ __ __ __ __ __ __ | 7
| __ __ 22 __ 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 *44 __ __ __ __ | 4
| __ __ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
How to continue ?
Just one more idea unlocks the puzzle
with singles to the end.
Update (Jan 01, 2026)
Now: if (02)c2|(02)b3, the path 01 -> 08
must to through cells b3,c2,b1,a1,a2,a3
(marked with xx in the grid), blocking
the connection 26->31.
,-----------------------------,
| __ __ __ __ __ __ __ | 7
| __ __ 22 __ 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 *44 __ __ __ __ | 4
| xx xx 01 43 __ __ __ | 3
| xx 31 xx 34 __ __ 38 | 2
| xx xx __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
So: 2.(02)d4!!
,-----------------------------,
| __ __ __ __ __ __ __ | 7
| __ __ 22 __ 19 __ 49 | 6
| __ 26 45 __ __ __ __ | 5
| __ 08 *44 *02 __ __ __ | 4
| __ __ 01 43 __ __ __ | 3
| __ 31 __ 34 __ __ 38 | 2
| __ __ __ __ __ __ __ | 1
'-----------------------------'
a b c d e f g JCO#7
The (03) location is still undetermined,
but the locations for 04,05,06,07 are
determined. From this, the puzzle is
unlocked and the remaining numbers
can be found easily.
Created: February 12, 2024
Contact: sudo.jco.br@gmail.com