UKPA Open Sudoku and Puzzle Tournament 2018
UKPA Open Sudoku and Puzzle Tournament 2018
The majority of the instruction booklets and schedule for the UKPA Open Sudoku and Puzzle Tournaments 2018 have now been published. I will get the remaining booklets out shortly.
If anyone else would like to take part then we still have some availability, please do not hesitate to contact me at liane@ukpuzzles.org . Further information can be found at: http://www.ukpuzzles.org/ukopen_2018.php .
If anyone has any queries regarding any of the puzzles, please post your queries on this thread and we’ll endeavour to answer them as quickly as possible. Please identify the round/puzzle in your query. Please don’t hesitate to ask a question about any of the puzzles. The instruction booklets contain examples of the different puzzles. Some examples may be straightforward showing the basic rules of the puzzle whereas others may have been taken from previous competitions and may possibly be harder than the actual competition puzzle. Points for puzzles are an indication of their difficulty based on the test solving, however, you may find your own experience differs.
Aids such as calculators are strictly forbidden. The majority of people solve the puzzles in pencil and an eraser is generally a very useful item to bring along. You are of course welcome to solve in pen also, but if you make a mistake it is harder to resolve. The puzzle booklets will include the instructions for the puzzles but not examples, therefore, if you do want to look at an example, then please bring your instruction booklets with you. You may make notes on the instruction booklets. Some people bring along spare paper (squared is useful). You will only be provided with one competition booklet for each round.
We are indebted to the fantastic puzzle authors from around the world who once again have created some wonderful puzzles for this competition – without them this would not be possible.
Sudoku authors are (by round) Puzzler Media, Norihiko Fujimaki, Masahiro Kaneko, Tetsuya Nishio, Minako Sakai, Yukio Sugimoto, Tatsuya Yamamoto, Zuzana Hromcová, Rishi Puri and David McNeill.
Puzzle authors are (by round): Serkan Yürekli and his students: Alen Zare Nisan, Arhan Alp, Aris Dikran Nisan, Bahar Acilan, Bersu Berker, Cumhur Aygar, Efe Alan, İlay Zehra Senay, Kubilay Berkant Simsek, Muhammed Ates, Mustafa Koyuncu, Mücahit Erdoğan Ünlü, Okan Tezcan, Ozan Kaya, Senem Isik, Serdar Sungun, Sakir Sacit Aydin, Utku Eren Akbaba, Yunus Emre Büyükkale, Yusuf Zeki Cetinkaya; Philipp Weiß, Nikola Živanović, Bram de Laat, Prasanna Seshadri and Tawan Sunathvanichkul.
Thanks also goes to all the test solvers: Bram de Laat, David McNeill, James McGowan, Martina Prinerova, Nikola Živanović, Prasanna Seshadri, Steve Barge, Yuhei Kusui and Zuzana Hromcová.
If anyone completes a round early then five bonus points per full minute saved will be awarded if all puzzles are solved correctly. If there is one small mistake then half bonus will be awarded. Two rounds (one Sudoku and one Puzzle) have partial points awarded in the event that the solver does not complete the full round.
In addition to the main prizes we have special awards for the best International competitor, best UK competitor and best Newcomer
If anyone has any special dietary requirements that I’m not aware of please can you let me know.
If anyone is only registered to take part in the Sudoku Tournament they will be more than welcome to stay and take part in the first round of the Puzzle Tournament – please let me know so that I can ensure I will have enough puzzle booklets available.
The team rounds on both days are fun events giving people practice of working together in a team and the teams will be selected by the organisers. Any guests that are accompanying competitors will be more than welcome to take part.
For those staying on Saturday evening, after the evening meal my daughter Alex has organised a quiz for a bit of light entertainment. Again, all guests and anyone not staying over on the Saturday evening will be welcome to join in. It won’t be going on too late – she has to get the Megabus back to Manchester afterwards.
Please note there is a slight difference to the schedule to that published on the main webpage. I hope that this will not cause any problems to those not staying over. Please let me know if there is an issue.
If anyone else would like to take part then we still have some availability, please do not hesitate to contact me at liane@ukpuzzles.org . Further information can be found at: http://www.ukpuzzles.org/ukopen_2018.php .
If anyone has any queries regarding any of the puzzles, please post your queries on this thread and we’ll endeavour to answer them as quickly as possible. Please identify the round/puzzle in your query. Please don’t hesitate to ask a question about any of the puzzles. The instruction booklets contain examples of the different puzzles. Some examples may be straightforward showing the basic rules of the puzzle whereas others may have been taken from previous competitions and may possibly be harder than the actual competition puzzle. Points for puzzles are an indication of their difficulty based on the test solving, however, you may find your own experience differs.
Aids such as calculators are strictly forbidden. The majority of people solve the puzzles in pencil and an eraser is generally a very useful item to bring along. You are of course welcome to solve in pen also, but if you make a mistake it is harder to resolve. The puzzle booklets will include the instructions for the puzzles but not examples, therefore, if you do want to look at an example, then please bring your instruction booklets with you. You may make notes on the instruction booklets. Some people bring along spare paper (squared is useful). You will only be provided with one competition booklet for each round.
We are indebted to the fantastic puzzle authors from around the world who once again have created some wonderful puzzles for this competition – without them this would not be possible.
Sudoku authors are (by round) Puzzler Media, Norihiko Fujimaki, Masahiro Kaneko, Tetsuya Nishio, Minako Sakai, Yukio Sugimoto, Tatsuya Yamamoto, Zuzana Hromcová, Rishi Puri and David McNeill.
Puzzle authors are (by round): Serkan Yürekli and his students: Alen Zare Nisan, Arhan Alp, Aris Dikran Nisan, Bahar Acilan, Bersu Berker, Cumhur Aygar, Efe Alan, İlay Zehra Senay, Kubilay Berkant Simsek, Muhammed Ates, Mustafa Koyuncu, Mücahit Erdoğan Ünlü, Okan Tezcan, Ozan Kaya, Senem Isik, Serdar Sungun, Sakir Sacit Aydin, Utku Eren Akbaba, Yunus Emre Büyükkale, Yusuf Zeki Cetinkaya; Philipp Weiß, Nikola Živanović, Bram de Laat, Prasanna Seshadri and Tawan Sunathvanichkul.
Thanks also goes to all the test solvers: Bram de Laat, David McNeill, James McGowan, Martina Prinerova, Nikola Živanović, Prasanna Seshadri, Steve Barge, Yuhei Kusui and Zuzana Hromcová.
If anyone completes a round early then five bonus points per full minute saved will be awarded if all puzzles are solved correctly. If there is one small mistake then half bonus will be awarded. Two rounds (one Sudoku and one Puzzle) have partial points awarded in the event that the solver does not complete the full round.
In addition to the main prizes we have special awards for the best International competitor, best UK competitor and best Newcomer
If anyone has any special dietary requirements that I’m not aware of please can you let me know.
If anyone is only registered to take part in the Sudoku Tournament they will be more than welcome to stay and take part in the first round of the Puzzle Tournament – please let me know so that I can ensure I will have enough puzzle booklets available.
The team rounds on both days are fun events giving people practice of working together in a team and the teams will be selected by the organisers. Any guests that are accompanying competitors will be more than welcome to take part.
For those staying on Saturday evening, after the evening meal my daughter Alex has organised a quiz for a bit of light entertainment. Again, all guests and anyone not staying over on the Saturday evening will be welcome to join in. It won’t be going on too late – she has to get the Megabus back to Manchester afterwards.
Please note there is a slight difference to the schedule to that published on the main webpage. I hope that this will not cause any problems to those not staying over. Please let me know if there is an issue.
 Attachments

 Schedule2018.pdf
 (221.38 KiB) Downloaded 413 times

 Instruction Booklet 2018  Sudoku Round 1.pdf
 (135.88 KiB) Downloaded 372 times

 Instruction Booklet 2018  Sudoku Round 2.pdf
 (756.35 KiB) Downloaded 364 times

 Instruction Booklet 2018  Sudoku Round 3.pdf
 (379.15 KiB) Downloaded 357 times

 Instruction Booklet 2018  Sudoku Round 4.pdf
 (135.85 KiB) Downloaded 354 times

 Instruction Booklet 2018  Sudoku Round 5.pdf
 (993.19 KiB) Downloaded 357 times

 Instruction Booklet  Puzzle Round 2  UKPA Open 2018.pdf
 (335.9 KiB) Downloaded 364 times

 Instruction Booklet  Puzzle Round 3  UKPA Open 2018  Nikola.pdf
 (342.39 KiB) Downloaded 375 times

 Instruction Booklet  Puzzle Round 4  UKPA Open 2018.pdf
 (424.36 KiB) Downloaded 366 times

 Instruction Booklet  Puzzle Round 6  UKPA Open 2018  Nikola.pdf
 (235.62 KiB) Downloaded 364 times
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Puzzle Round 1 now uploaded.
 Attachments

 Instruction Booklet  Puzzle Round 1  UKPA Open 2018.pdf
 (176.71 KiB) Downloaded 365 times
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Liane,
Thanks for posting.
On round 3 of the sudoku tournament (Linked puzzles) I found the small grid explaining which rules applied where slightly confusing  do the rules apply to each 9x9 grid (including the overlapping cells)?
In particular do the rules for C apply to the 81 cells in the centre (the diagram makes it look like they only apply to the central 9 cells which cannot be right)?
I also assume in the actual puzzle grid that the colours of shading will be consistent (which they don't appear to be in the instruction book) so that if there is a shaded cell in an overlapping 3x3 block it will have to obey the rules of a shaded cell in each different 9x9 grid (I don't think my eyes are good at distinguishing minor variations in shades of grey)  also if a shaded cell has no meaning in a puzzle type I assume any shading will be irrelevant for the purposes of the overlapping puzzle?
Thanks,
Michael
Thanks for posting.
On round 3 of the sudoku tournament (Linked puzzles) I found the small grid explaining which rules applied where slightly confusing  do the rules apply to each 9x9 grid (including the overlapping cells)?
In particular do the rules for C apply to the 81 cells in the centre (the diagram makes it look like they only apply to the central 9 cells which cannot be right)?
I also assume in the actual puzzle grid that the colours of shading will be consistent (which they don't appear to be in the instruction book) so that if there is a shaded cell in an overlapping 3x3 block it will have to obey the rules of a shaded cell in each different 9x9 grid (I don't think my eyes are good at distinguishing minor variations in shades of grey)  also if a shaded cell has no meaning in a puzzle type I assume any shading will be irrelevant for the purposes of the overlapping puzzle?
Thanks,
Michael
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Hi Michael, the rules apply to each 9x9 grid including the overalapping cells, so for C it is the full 81 cells in the centre of the puzzle. Those rules will only apply to that particular part of the puzzle, so, for example, the untouchable rule for C only applies to those 81 cells in the centre and not any adjacent ones.MichaelC wrote: ↑Thu 22 Feb, 2018 11:00 pmLiane,
Thanks for posting.
On round 3 of the sudoku tournament (Linked puzzles) I found the small grid explaining which rules applied where slightly confusing  do the rules apply to each 9x9 grid (including the overlapping cells)?
In particular do the rules for C apply to the 81 cells in the centre (the diagram makes it look like they only apply to the central 9 cells which cannot be right)?
I also assume in the actual puzzle grid that the colours of shading will be consistent (which they don't appear to be in the instruction book) so that if there is a shaded cell in an overlapping 3x3 block it will have to obey the rules of a shaded cell in each different 9x9 grid (I don't think my eyes are good at distinguishing minor variations in shades of grey)  also if a shaded cell has no meaning in a puzzle type I assume any shading will be irrelevant for the purposes of the overlapping puzzle?
There will be two types of 'decoration' on the actual puzzle which will be completely clear and yes if there is any 'shading' of an overlapping cell then it will have no relevance to the overlapping puzzle. The example types have been taken from examples for previous competitions, hence, the differences.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Hi Liane. Have I missed the instructions for Round 5?
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Hi liane, just to be 100% sure, when you say there will be two types of decoration, does that mean for instance that where D and E meet, the different colour of a particular cell will indicate whether it should follow the rules of either d or e provided both have shaded cells rules?puzzlemad wrote: ↑Fri 23 Feb, 2018 9:28 amHi Michael, the rules apply to each 9x9 grid including the overalapping cells, so for C it is the full 81 cells in the centre of the puzzle. Those rules will only apply to that particular part of the puzzle, so, for example, the untouchable rule for C only applies to those 81 cells in the centre and not any adjacent ones.MichaelC wrote: ↑Thu 22 Feb, 2018 11:00 pmLiane,
Thanks for posting.
On round 3 of the sudoku tournament (Linked puzzles) I found the small grid explaining which rules applied where slightly confusing  do the rules apply to each 9x9 grid (including the overlapping cells)?
In particular do the rules for C apply to the 81 cells in the centre (the diagram makes it look like they only apply to the central 9 cells which cannot be right)?
I also assume in the actual puzzle grid that the colours of shading will be consistent (which they don't appear to be in the instruction book) so that if there is a shaded cell in an overlapping 3x3 block it will have to obey the rules of a shaded cell in each different 9x9 grid (I don't think my eyes are good at distinguishing minor variations in shades of grey)  also if a shaded cell has no meaning in a puzzle type I assume any shading will be irrelevant for the purposes of the overlapping puzzle?
There will be two types of 'decoration' on the actual puzzle which will be completely clear and yes if there is any 'shading' of an overlapping cell then it will have no relevance to the overlapping puzzle. The example types have been taken from examples for previous competitions, hence, the differences.
Thanks!
PS, slightly off topic, are there parking facilities at the hotel?
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Sudoku Round 3.
The centre puzzle has no 'decoration' applicable to it.
There are two types of decoration  one type for puzzles A and E and the other for B and D.
If that decoration overlaps onto other puzzles then it only applies to the one.
So, the blue decoration in the picture only applies to puzzle B and the red decoration only applies to puzzle E. I hope that this clarifies this.
The hotel website does say free car parking places.
For those coming by train into East Croydon  their website says the 119 bus stops outside the hotel.
The centre puzzle has no 'decoration' applicable to it.
There are two types of decoration  one type for puzzles A and E and the other for B and D.
If that decoration overlaps onto other puzzles then it only applies to the one.
So, the blue decoration in the picture only applies to puzzle B and the red decoration only applies to puzzle E. I hope that this clarifies this.
The hotel website does say free car parking places.
For those coming by train into East Croydon  their website says the 119 bus stops outside the hotel.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Hi Liane
Thank you. A couple of questions, although I think I know the answers!
In the 'LITS' puzzle in Puzzle comp round 1, does 'regardless of' really mean 'including''? it is ambiguous whether different rotations/reflections of the same tetromino can or cannot touch (although I'm pretty sure they can't).
In 'Geradeweg' in round 2, if the number is at a corner of the loop, do both lines emanating from it need to be the same length?
In 'Magic R' in round 3, do all the given letters have to be used? (Again I suspect so, but it's not explicit)
There are some sample puzzles that are simpler than the rules suggest (e.g. Doppelblock), it might be worth mentioning that.
Looking forward to the competition!
Angus
Thank you. A couple of questions, although I think I know the answers!
In the 'LITS' puzzle in Puzzle comp round 1, does 'regardless of' really mean 'including''? it is ambiguous whether different rotations/reflections of the same tetromino can or cannot touch (although I'm pretty sure they can't).
In 'Geradeweg' in round 2, if the number is at a corner of the loop, do both lines emanating from it need to be the same length?
In 'Magic R' in round 3, do all the given letters have to be used? (Again I suspect so, but it's not explicit)
There are some sample puzzles that are simpler than the rules suggest (e.g. Doppelblock), it might be worth mentioning that.
Looking forward to the competition!
Angus
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Hi Angus,Angus wrote: ↑Sun 25 Feb, 2018 12:47 pmHi Liane
Thank you. A couple of questions, although I think I know the answers!
In the 'LITS' puzzle in Puzzle comp round 1, does 'regardless of' really mean 'including''? it is ambiguous whether different rotations/reflections of the same tetromino can or cannot touch (although I'm pretty sure they can't).
In 'Geradeweg' in round 2, if the number is at a corner of the loop, do both lines emanating from it need to be the same length?
In 'Magic R' in round 3, do all the given letters have to be used? (Again I suspect so, but it's not explicit)
There are some sample puzzles that are simpler than the rules suggest (e.g. Doppelblock), it might be worth mentioning that.
Looking forward to the competition!
Angus
Round 1 LITS  Rotations and/or reflections of the same tetromino type are not allowed to touch.
Round 2 Geradeweg  You are correct. The example shows the 1 and the 3 to be where the loop turns but the 2' have the loop passing straight through.
Round 3 Magic R  All given letters have to be used, as is the case in all puzzles in this round.
You are also right that sample puzzles may well be easier than the competition puzzles. The round 4 Doppelbock, I realise that I have missed the '(1 to 3 in the example').
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Fast and helpful, many thanks!
Latin pointers is also simpler in the example, by the way, and I've noticed that round one says '3th to 4th March'!
Latin pointers is also simpler in the example, by the way, and I've noticed that round one says '3th to 4th March'!
Re: UKPA Open Sudoku and Puzzle Tournament 2018
There may well be others were I've missed that the example doesn't use as many numbers etc.  so apologies for any others that I've missed.
Round one  Serkan and his students did all the work preparing the instruction booklet (and everything else) for that round so I think we can forgive their mistranslation from Turkish.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Just to remind everyone that this year the event is at a hotel on the Purley Way and NOT at the usual venue.
https://www.hallmarkhotels.co.uk/hotels ... irections/
David
https://www.hallmarkhotels.co.uk/hotels ... irections/
David
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Puzzle round 5 instructions now available. Apologies for the delay to these.
An amended version is posted further on in the thread  slight change to wording of last two puzzles.
An amended version is posted further on in the thread  slight change to wording of last two puzzles.
 Attachments

 Instruction Booklet  Puzzle Round 5  UKPA Open 2018.pdf
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Re: UKPA Open Sudoku and Puzzle Tournament 2018
In round 5, Akari Blocks, what is the definition of a 'block'? Is it any contiguous set of black squares?
In round 5, Place by Product and Place by Product Repeat, I presume that "the lengths of" is intended to be inserted, to give "Numbers outside the grid give the product of the lengths of the nonpentomino spaces"?
In round 5, Place by Product and Place by Product Repeat, I presume that "the lengths of" is intended to be inserted, to give "Numbers outside the grid give the product of the lengths of the nonpentomino spaces"?
Re: UKPA Open Sudoku and Puzzle Tournament 2018
In the antisymmetry Rossi Sinai, when it discusses 180 degree symmetry, is it within the cage, or the whole grid, or both? The example implies the whole grid, but I thought there was a chance the example was wrong.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
It is the whole grid that the symmetry applies to.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Yes a block is a contiguous set of black cells.GarethMoore wrote: ↑Tue 27 Feb, 2018 12:36 amIn round 5, Akari Blocks, what is the definition of a 'block'? Is it any contiguous set of black squares?
You are correct. I will amend the instruction booklet with this.GarethMoore wrote: ↑Tue 27 Feb, 2018 12:36 amIn round 5, Place by Product and Place by Product Repeat, I presume that "the lengths of" is intended to be inserted, to give "Numbers outside the grid give the product of the lengths of the nonpentomino spaces"?
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Puzzle Round 5  V2. Words added to instruction regarding last two puzzles as per previous post.
 Attachments

 Instruction Booklet  Puzzle Round 5  UKPA Open 2018 V2.pdf
 (735.2 KiB) Downloaded 226 times
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Sorry for the questions, but I am relatively new here...
3: Rassi Silai  presumably you don't have to draw in the lines separating the rope cells within the same regions as in the given solution?
15: Place by Product  is the little dash in the starting grid extraneous or does it mean a cell that should remain empty?
3: Rassi Silai  presumably you don't have to draw in the lines separating the rope cells within the same regions as in the given solution?
15: Place by Product  is the little dash in the starting grid extraneous or does it mean a cell that should remain empty?
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Round 6  filename suggests puzzles are by Nikola, the file itself says Tawan
Round 5  I'm being anal here, but I don't think the rules to Rassi Silai are stated properly. If ropes are entirely self contained within their respective regions, how on earth is it possible for the ends to touch? Even in the case where cells containing the ends of different ropes share edges and/or corners?
Similar complaint for place by product. Pentominos sharing an edge presumably are no longer pentominos, and it feels more accurate to talk about sharing corners or touching at a point rather than the vague and imprecise "touching diagonally". The constraint isn't on the pentominos per se, rather the cells in which they are being placed.
Similar complaint for snake, although the concept of the snake touching itself is more intuitive than talking about shared edges/corners.
(I do appreciate the authors are probably supplying the rules and editing them for optimal clarity is a lower priority here)
Round 5  I'm being anal here, but I don't think the rules to Rassi Silai are stated properly. If ropes are entirely self contained within their respective regions, how on earth is it possible for the ends to touch? Even in the case where cells containing the ends of different ropes share edges and/or corners?
Similar complaint for place by product. Pentominos sharing an edge presumably are no longer pentominos, and it feels more accurate to talk about sharing corners or touching at a point rather than the vague and imprecise "touching diagonally". The constraint isn't on the pentominos per se, rather the cells in which they are being placed.
Similar complaint for snake, although the concept of the snake touching itself is more intuitive than talking about shared edges/corners.
(I do appreciate the authors are probably supplying the rules and editing them for optimal clarity is a lower priority here)
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Don't apologise for the questions  better to get the queries sorted now.Angus wrote: ↑Tue 27 Feb, 2018 8:31 amSorry for the questions, but I am relatively new here...
3: Rassi Silai  presumably you don't have to draw in the lines separating the rope cells within the same regions as in the given solution?
15: Place by Product  is the little dash in the starting grid extraneous or does it mean a cell that should remain empty?
3: Rassi Silai  no you don't have to draw in the lines separating the cells within the region  the example was taken from the 2017 WPC instruction booklet and I hadn't realised that they'd been put in.
15: Place by Product  my omission in the rules. "Any cell containing a dash '' shall remain unshaded." This applies to both puzzle 15 and puzzle 16. I will amend the instruction booklet.
Re: UKPA Open Sudoku and Puzzle Tournament 2018
Copy/Paste error in the file name  the puzzle set is by Tawan.
The example was taken from the WPC2017 instructions and doesn't show the possibility. If, for example, you have a 2x3 area, as this sample, then the first option is not allowed but the 2nd is.detuned wrote: ↑Tue 27 Feb, 2018 10:29 amRound 5  I'm being anal here, but I don't think the rules to Rassi Silai are stated properly. If ropes are entirely self contained within their respective regions, how on earth is it possible for the ends to touch? Even in the case where cells containing the ends of different ropes share edges and/or corners?
Some people may consider that they have placed two pentominoes, even if they touch rather than one 10 cell polymino. People may shortcut how they actually draw the pentominoes, though normally in examples and solutions then the cells are fully shaded, hence the 'touching diagonally'. The instruction for this puzzle was amended a bit from a previous version and in doing so I've omitted the part about cells having a dash in them having to remain unshaded. This will be fixed in v3 of this booklet.detuned wrote: ↑Tue 27 Feb, 2018 10:29 amSimilar complaint for place by product. Pentominos sharing an edge presumably are no longer pentominos, and it feels more accurate to talk about sharing corners or touching at a point rather than the vague and imprecise "touching diagonally". The constraint isn't on the pentominos per se, rather the cells in which they are being placed.
Again, normal convention on instructions and answers is for the snake to occupy each cell fully, although in practice people do shortcut the answer by drawing a single line.

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Re: UKPA Open Sudoku and Puzzle Tournament 2018
Yes  that's a good point, and a problem with adding unnecessary precision to definitions. Usually a general description plus an example solution will work much better than attempting to talk about edges, points, contiguity and so on.
Most puzzle rules make assumptions, such as e.g. that you can only place one segment/digit in a single square, so the secret is to balance brevity (and therefore hopefully clarity) against overprecision when then often leads to obfuscation. Snake is a particularly tricky one, since really to define a snake it needs to say that squares greater than two squares apart along the length of the snake cannot touch, either on a side or diagonally, but then once you add that it becomes so precise that you really also need to define that it can't branch off in two directions, and perhaps be clearer about the overall path concept too. But in all honesty, showing a picture of a snake makes it pretty clear, I think.
All that said, puzzle instructions often end up being unnecessarily imprecise and so avoiding that is definitely a good aim!