Puzzle #172: Tapa; Circled

This is the last of three posts with new Tapa variants for the TVC.

The last variant is Circled Tapa. It is based on Black and White Snake. As there is already a Black and White Tapa, I couldn't go with that name. My second thought was Dotted Tapa, but then I remembered Prasanna's Dotted Tapas. So lastly I settled on Circled Tapa, by just changing the wording of the rules. The variant here is that the Tapa wall is built up of alternating black and white circles. The clues indicate how many circles of a particular colour there are around it, instead of the number of coloured cells.

Rules for Tapa

In this Tapa the wall is made up of alternating black and white circles. There are black and white clue cells. White clue cells indicate the amount of white circles in the orthogonally connected sections of the wall around that cell. Black clue cells indicate the amount of black circles in the orthogonally connected sections of the wall around that cell. Each digit indicates a section of at least length 1.



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Daily League #55: Odd Labyrinth Sudoku

The second puzzle in the Odd Sudoku series is an Odd Labyrinth Sudoku. I always enjoy solving these puzzles. It has a bit of puzzling in them, which always suits me well. You also get to create an odd/even grid, which is something I always enjoy. Parity variants always seem to suit me well.

In the design I tried to find some interesting deductions in this genre. If that totally worked, I'm not sure, but I had fun designing it. I didn't bother resolving any old puzzles, so it could be that this has been used before. It took a while to construct a valid puzzle though, as too often some of my logic led to no path existing. I think I lost some of the interesting things because I also had to make it unique, but it should still be a fun solve.

Rules for Sudoku

In this Sudoku there has to be a path that runs from the left top corner to the right bottom corner over cells that contain odd digits. This path can only travel horizontally and vertically.

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Puzzle #171: Tapa; Castle

This is the second post of three new Tapa variants for the currently ongoing TVC.

This time the variant is Castle Tapa. This variant is based on the Castle Wall genre, hence the name. It also has some similarities to No Islands Tapa. There haven't been many variants that use different coloured clues. The rule is that all black clue squares are contained within the Tapa wall and white clue squares remain outside the Tapa wall. I now realise this is the exact opposite from Castle Wall, but I don't think it matters. The puzzle turned out well, in my opinion.

Rules for Tapa

This Tapa has black and white clue cells. White clue cells must always be outside the Tapa wall. You must always be able to reach the edge of the grid from them by travelling horizontally and vertically through uncoloured cells and/or clue cells. Black clue cells must always be inside the Tapa wall. You must not be able to reach the edge of the grid from them by travelling horizontally and vertically through uncoloured cells and/or clue cells.

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Puzzle #170: Tapa; Lonely

With the TVC having started again, I gave designing a few new variants a go. I find it more fun if a TVC has a few new variants in it. For the next 3 days I will post 3 new variants.

The first one is Lonely Tapa. This rule has already been in effect in one genre, namely Tapa Islands. This rule is that an orthogonally connected uncoloured area can only contain at most one clue cell. I was actually kind of surprised it wasn't already in this list as it seemed like such a simple rule. I think the puzzle worked out well.

Rules for Tapa

In this Tapa, any orthogonally connected uncoloured area can contain at most one clue cell.

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TVC XVII Recap

The first TVC of the season is over. I finished in 8th place, finishing all puzzles with 9 seconds to spare. It wasn't my best solve, but I'm still happy with it.
I had a bit of a slow start on the Alternative Tapa. I was a bit slow utilising the letters. I could have used uniqueness to finish it quicker, but I wasn't 100% sure if it held up. It just looked that uniqueness couldn't be guaranteed otherwise.
The next puzzle that caused problems was the second Skyscrapers Tapa. That was mostly because I forgot a 6 Tapa clue always needs one of two opposite edges coloured. I was treating it as a 5 clue and didn't see the opening. I got through I okay with a guess.
Then the Star Tapa held me up a bit, but luckily my own puzzle had given me some practise with the stars I needed here.
The last puzzle that caused problems was the second Magic Tapa. It actually caused the most problems and I had to restart it. Even on the restart I couldn't solve it, by which it was time to enter the codes. I was afraid I wouldn't solve it in time. But after entering the codes, I realised I had been treating a 2 as a 3 the whole time. So I could quickly solve the end and answer the key within a minute and claim my bonus of 0.2 points.

I think I got the most use out of designing my Tapa Star and Tapa Magic puzzles. I don't know which of my example puzzles were most useful for others. The feedback on my practise puzzles is getting less over the years. I don't know if it is because people don't need or want them anymore or if it's just because they have come to expect them. Some feedback would be appreciated as it takes a bit of work to push out all ten Tapas in the few days between the instruction booklet coming out and the start of the contest.

Lastly, the secret Tapa I mentioned in Part 2. The Tapa With Borders grid is also solvable as a 10x10 classic Tapa. I realised from the design that all outside clues were completely irrelevant to the Tapa with Borders logic. So I decided to clue them so that they would make a unique Tapa with the rest of the clues. I thought it was a fun touch.

Rules for Tapa

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Daily League #54: Odd Sudoku

I had a few ideas for the next theme. One of them I couldn't really get to work the way I wanted. I had 2 puzzles that worked, but I didn't see me managing to find any more. Another theme has been done a few times by Fred Stalder, so I'll leave that one for later. The other theme might have been badly received by the same Fred Stalder, so I figured that's not the best way to start of the new year. So after rejecting a few themes, I settled on a simple one. This theme is Odd. It's not very original. As I don't write many classic variants, I figured it would be nice to write a simple variant for once.

The first puzzle is of course just a normal Odd Sudoku. I'm happy how it turned out. I think it looks nice with the four circle layout. It took a few tries as I kept having to add clues in other places to make it unique. It's not a hard puzzle, so it will probably be solved a lot more than some of my other puzzles. I hope people at least enjoy it.

Rules for Sudoku

In this Sudoku, grey cells must contain odd digits only.

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TVC XVII Practise: Part 2

Here's the second part of the practise puzzles for TVC XVII. I didn't have as much time to make puzzles during New Years. We also went to see the new Star Wars move today. That took up some more time. A few variants I had some trouble making, so that they would be a bit interesting. I think they should help getting used to the variants.

The first puzzle is an Alternative Tapa. It's not too hard a puzzle. I haven't found a good way to make this variant to be influential, instead of just using it to make the puzzle unique. At least it looks nice and still fun to solve.
The second puzzle is a Tapa with Borders. I thought making the size a bit smaller would make it a bit more interesting. Although a 6x6 Tapa is not very interesting. But finding the grid will take a bit longer.
The third puzzle is a TAPA LOGIC. I think this is a nice puzzle. It was at least fun to think of the logic involved here. It should be fun to solve too.
The fourth puzzle is a Make Room For Tapa. This one took a bit of effort to make. I first tried to make the rooms fit some randomly chosen clues, but I couldn't make that work. So instead I designed the rooms first and then figured out which clues would create a unique puzzle.
The fifth puzzle is a Tapa Star. This is definitely the hardest puzzle in the set. I kept coming up with puzzles without a valid Star distribution. It is easy to create a Tapa wall without a star pattern apparently. You really need to work the stars to get to the solution in this puzzle. Approach it carefully.

I hope this set is again helpful and enjoyable. Don't forget about the secret Tapa.

Puzzles can be found below.

TVC XVII Practise: Part 1

This is the first selection of practise puzzles for the upcoming TVC XVII. I only came aware this was starting again today, so I'm trying to get all puzzles out by Friday. This post will feature the first five puzzles.

The first puzzle is a Peers Tapa. I like the idea of this variant. I always enjoy Tapas that have the same sum in symmetrical clues. This variant forces that. The puzzle turned out reasonably well. It's one of the easier practise puzzles.
The second puzzle is a Tapa Skyscrapers. The variant can drive a lot of the puzzle, so I tend to just place some random, but nice looking, Tapa clues and make the variant drive the rest of the puzzle. I think it worked out well in this puzzle. It's not an overly hard puzzle, but you have to understand how to use the variant.
The third puzzle is a Knapp Daneben Tapa. I always have trouble with 1s turning into 0s when designing Knapp Daneben puzzles. I tried to avoid the issue as much as possible. My personal goal when designing Knapp Daneben puzzles is always to try to only use valid Tapa clues and not use combinations of digits in a cell that would not be allowed in a normal Tapa.
The fourth puzzle is an Outside Tapa. The first Outside Tapa I wrote I used a lot more Tapa clues, but I went for a lower number of clues this time and have the variant drive the solve a bit more. It turns out that using more equal symbols reduces the need for clues. I think it turned out well. This is probably the hardest puzzle in this set.
The fifth puzzle is a Tapa Magic. I'm not that much a fan of this variant. I always feel I have to use too many clues, because the restrictions won't allow it to be unique otherwise. It's still a nice puzzle and shows some of the tricks in this variant.

I hope these are helpful. Enjoy.

[Edit: Tapa Skyscrapers fixed.]

Puzzles can be found below.

TVC XVII Practise: Introduction

It seems 2016 is again a Tapa Variations Contest and Classic Tapa Contest year. That means that I'll actually have to defend my Tapa Master title I won in 2013 instead of the coasting on the honour without little effort. The CTC will run daily over 50 days from the 2nd of January 2016 till the 22nd of February 2016. The TVC will run in four contests over weekends between the 2nd of January 2016 and the 22nd of February 2016  The first of these contests, TVC XVII, will run from the 2nd of January 2016 till the 4th of January 2016.

TVC XVII will contain 10 variations. These variations are Alternative Tapa, Tapa with Borders, TAPA LOGIC, Peers Tapa, Tapa Skyscrapers, Make Room For Tapa, Tapa Star, Knapp Daneben Tapa, Outside Tapa and Tapa Magic. These are all variations that have previously appeared in other TVCs. So for practise you can check out older TVC's. In this post I will post the puzzles I shared before as practise for older TVCs. I will also be posting new examples for all these type in other posts. I hope they will all be useful in preparation. But not too much as I'd like to be the first to successfully defend a Tapa Master title.

Puzzles can be found below.

Daily League #53: Quad Division Sudoku

This is the fourth and last Sudoku in the 'Quad Sudoku' series. It's as far as I know a new variant. I wish I could check somewhere what variants have been done already. I though it would be nice to have a variant where the four cells were treated as two two-digit numbers. I considered turning the Diagonal Difference puzzle from instructionless round of the last WPC into a Sudoku, but I had already made a Quad puzzle with differences. Then I figured I could do something similar with division.
I just started playing around with a few placements and I noticed that the clues carry a lot of impact. They give you a lot of information and you get placements pretty quick. So I figured it should be possible to make one without any givens. I always enjoy trying to turn out Sudokus without any givens, which most people doing my Daily League puzzles must have noticed. This puzzle had an opening constructed pretty quickly. The problem of course was to get it unique with only valid clues. I had a few puzzles that were close but I couldn't get any valid clues in anymore to make it unique. After a few tries, this puzzle came out. I don't think it's overly hard, but it does involve a bit of careful calculations to make sure you don't make any errors. There's very little chance to track back.

Rules for Sudoku

In this Sudoku, a number on a grid point indicates the result of dividing the two-digit number formed by the top two digits by the two-digit number formed by the bottom two digits. Both two-digit numbers have to be read from left to right.

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Daily League #52: Quad Max Sudoku

This is the third puzzle in the 'Quad Sudoku' series. This time once again a common variant. I picked this type as it's not an arithmetic variant and many of the Quad variants are arithmetic in nature. It's also a type that I enjoy solving.
In the design I wanted to see how far I could get with just Quad Max clues. I knew that eventually had to use givens as there is no way to differentiate between 1s and 2s with these clues. I think the design worked out well. The puzzle in the end has four givens. One of them is not necessary for uniqueness, but I wanted to keep the symmetry and it didn't ruin the solving path. The last few digits are a bit tricky, but I thought it was okay with so few digits remaining.

Rules for Sudoku 

In this Sudoku, an arrow on a grid point points to the highest digit in the four cells around it. Digits may repeat around an arrow, but the highest digit is always unique.

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Daily League #51: Quad No Difference Sudoku

This is the second puzzle in the 'Quad' Sudoku series. As far as I'm aware this is a new variant. It's the first puzzle I wrote for this series. I just thought it would be better to open the series with something more common. I thought the variant worked pretty nicely.
The design was a bit tricky. I had a different layout in mind, but I couldn't find a way to get that layout unique without giving digits around a clue. That was something I was trying to avoid as I think these Quad Sudokus look nicer when there are no digits given around the Quad clues. I changed the layout a bit in the left top and right bottom nonet. Originally the right bottom nonet was to get a Quad clue as well, but there was no way to force the 5 with such a clue. I needed that 5 for uniqueness. I still think it's a nice looking puzzle and it should be a good solve.

Rules for Sudoku

In this Sudoku, a clue given on a grid point indicates that no two of the four digits around it have this difference. E.g. a 3 clue indicates that no two of the four digits around it have a difference of 3.



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Daily League #50: Quadruple Sudoku

This month's theme is Quads. They will all be variants that with clues on grid points, that give information about the four cells around it. This set will contain two known variants and two new variants, as far as I'm aware. The choice for this theme came because I had an idea for a variant. I made a Sudoku with it and I think it turned out nicely. I figured it would make a good theme as there are many variants that use such a clue.
The first Sudoku is the most common variant. It's a variant I've written once before, but never for the Daily League. It's what I consider a classic variant, because there are no alternative clues in it. I wanted to make one without any overlapping clues. It turned out nicely in my mind.

Rules for Sudoku

In this Sudoku digits given on a grid point indicate the digits in the four cells around it.

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Daily League #49: Descriptive Pairs or Next To Nine Sudoku

This is the fifth puzzle in my 'A or B Sudoku' series. It is a combination of Descriptive Pairs Sudoku and Next To Nine Sudoku. I thought I might be able to combine these genres as they both use two digits for clues.
These are two types that suit my design style a bit more, because I like designing Sudokus without any givens in the grid. It was a bit hard to find a good opening, so I went for a relatively obvious opening clue. The opening is pretty narrow and it takes a while for the solve to open up a bit. I'm pretty happy how it turned out. I thought the two types work well together.

Rules for Sudoku

In this Sudoku each pair of digits is either a Descriptive Pairs Sudoku clue or a Next To Nine Sudoku clue. In a Descriptive Pairs Sudoku clue, one of the digits indicates the position of the other digit in that row or column when looking from that side. A Next To Nine Sudoku clue indicates the two digits that border the 9 in that row or column. Different clues can conform to different rules.

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Daily League #48: Edge Sums or Frame Sudoku

This is the fourth puzzle in my 'A or B Sudoku' series. It's a combination between Edge Sums and Frame Sudoku.

These two type are pretty similar. One uses the sum of the first two cells and the other the sum of the first three cells. I find both types fun to solve, but I do think they get the same pretty fast. There's a few variations on them that make them a bit more interesting, like Hi-Lo Frame Sudoku and Frameless Sudoku. I thought the combination of the two and three cell sums might make it more interesting. I am happy with how the puzzle turned out, especially getting the ending to work with so few clues was fun to figure out. Hope you enjoy it too.

Rules for Sudoku

In this Sudoku the numbers on the outside indicate the sum of the digits in the first two or first three cells seen in that row or column from that direction. The number of digits can differ between different sums.

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Puzzle #169: Fortress Sudoku

For his last two puzzles for the Daily League, Tom Collyer has been playing around with the same layout in his Extra Region and Clone Sudoku and his Very Odd Sudoku. This second puzzle can be solved under a second rule. After having solved it both ways, I tried solving it under a few other rules that might be presented that way. None of them worked. But I found that solving it under Fortress Sudoku rules lead to some interesting deductions by removing a few of the givens. So with that opening, I started playing around a bit what givens would make it unique. This is the result. I think it turned out nicely.

Rules of Sudoku

In this Sudoku digits in grey cells are larger than all orthogonally adjacent white cells.

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Daily League #47: Palindrome Or Rising Sudoku

Here is the third puzzle in my 'A or B Sudoku' series. This time it is a combination between Palindrome Sudoku and Rising Sudoku. Rising Sudoku might be a bit unfamiliar. It's basically a Thermometer Sudoku without a bulb to indicate the low point of the line. I saw them more often years ago, but I think now Thermometer Sudoku has become a bit more the go-to genre.
I wasn't sure if this combination would work very well. It was a bit hard to figure out how to get a start in this Sudoku, without giving away too many givens. The construction was a bit troublesome as I ran into situations without a solution far too often. The problem was that a lot of areas wouldn't resolve themselves early in the solve and by the time they did, there would be a contradiction with clues I had laid out in the meantime. In the end, I think the puzzle worked out nicely.

Rules of Sudoku

In this Sudoku a grey line is either a Palindrome Sudoku or a Rising Sudoku clue. In a Palindrome Sudoku clue the digits along the grey line form a Palindromic sequence; the sequence can be read the same from either end. In a Rising Sudoku clue, the digits form a rising sequence from one end to the other. This sequence does not have to be an arithmetic sequence. Different grey lines can conform to different rules.

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Daily League #46: All Odd Or All Even Sudoku

This is the second puzzle in my 'A or B Sudoku' series. This time it's a combination of Odd and Even Sudoku.

This combination has been done before, but I've always enjoyed solving them. I generally like puzzles with parity. I used the same layout for this puzzle as one of my earlier puzzles, namely my Renban Sudoku (and in a sense my Arrow Sudoku). I thought this layout would work well for this genre and I was right. I found some interesting interactions in this layout. These interactions might lead to some harder logic, but they should be fun to figure out.

Rules for Sudoku

In this Sudoku grey cells within a single marked 3 by 3 area are either all odd or all even. This can differ between different areas.

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Daily League #45: Clone Or Extra Region Sudoku

After a Daily League hiatus of over a year, I've written a number of Sudokus again. I'm planning on keeping it up for a while.

For this month, all my Sudokus will fall in a particular theme. This theme is "A or B Sudoku". This means that clues for two different genres appear in the Sudoku and it's up to you to figure out which clues are part of which genre. The reason for this theme is that one of my favourite Sudokus I have written for the Daily League was my Ace Sudoku. I really enjoyed writing that puzzle, playing around with getting the different rules having to be used in different areas. I think it's a fun solve personally. So I started playing around with different rules that are normally presented in the same way. When I had a few out, I decided I would be posting them in the Daily League.
The first puzzle is a combination of Clone and Extra Region. I first searched for a nice layout that allowed for multiple 9 cell areas that don't touch each other. The three I-shaped regions look nice and work well together. I think the combination worked out well, but can probably be improved on a bit.

Rules for Sudoku

In this Sudoku each grey area is either an Extra Region Sudoku or a Clone Sudoku clue. A Extra Region Sudoku clue contains the digits 1~9 exactly once. A Clone Sudoku clue has the exact same digits in the same place as one or more of the other grey areas, without rotation or reflection. Different grey areas can obey different rules.

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Polish Puzzle Championship 2015

This weekend were the Polish Sudoku and Puzzle Championships. I was one of the puzzle contributors and test-solved all puzzles for the championship (and a few more that didn't appear). Both events were won by Jan Mrozowski. You can find all puzzles at the following links: Sudoku and Puzzle. (As a small note, there is a printing error in Round 4 (my puzzles). In the larger Summon puzzle, the 3 clue at the bottom should be a 9).

This post will contain all my puzzles that were used at the championships. I used a similar structure to my round as last year, with two puzzles of each type. I tried to get a good mix of different genres, both familiar and unfamiliar. I didn't use any of the types I used last year to keep mixing it up. There's enough genres to choose from, so it seems a bit weird to repeat a genre. I think it worked out well and would love to hear some feedback from the competitors.

Puzzles can be found below.

Puzzle #168: Statue Park, Summon

These three puzzles were originally written for the Polish Puzzle Championships being held the upcoming weekend. I aimed to write a similar set as last year, with 2 puzzles per genre. I again wrote 20 puzzles, but the test times were a bit long for a 60 minute round. I cut the Statue Park puzzles, because they didn't allow for reflection and that was the type that most likely would trip people up from that because of that.
This Summon puzzle was the original harder puzzle, but they both tested too long for their intention. So the smaller puzzle became the harder and I added a smaller puzzle to the set. I've started to like this genre better, but I still feel they somehow stay hard to solve. I think it's because it doesn't have a natural flow and it's sometimes hard to know where to look next. The logic is always solid, but it's easy to get stuck none-the-less.

Puzzles can be found below.

2014 Slovak Puzzle Championships

While going through my puzzle files, I came across the Slovak Championships folder. I realised I had never shared these puzzles on my blog. So I figured I might as well share them now.
I was contacted by Zuzanna Hromcova to write puzzles for their championship. We were given a number of categories to write puzzles in. One of the categories was non-grid puzzles, for which I provided three different genres; namely ABC Decoder, Dice and Mastermind. Dice and ABC Decoder are types I enjoy writing; Mastermind I didn't have that much experience with. But it was something I'd like to give a go.
The other categories I picked were Latin Squares and Division puzzles. For each type we had to write a standard genre and a variant on the genre. I picked Skyscrapers, with Haido as the variant. I like Skyscrapers and I thought Haido still had part of the Skyscraper logic, but used differently enough to make it not like solving four skyscraper puzzles.
For the Division set I picked ABCD Division, with Sum Division as the variant. It's a type I have seen a lot when I first started puzzling, but I haven't really seen it much since. I thought sums was an obvious variant, but I haven't really seen it this way much. I have seen a similar variant where the grid has to be divided into a complete set of pentominoes, but not really without this restriction.

I tried to put a bit of theming in the non-grid puzzles. I wrote a few nine digit ABC Decoders for the 2014 24 hour championships, and I thought that was a good size to use in a championship. The letters spell out THE SLOVAK, which was the nicest way I could use nine different letters to write something Slovakia related. I found some words with opposite meanings in the letter set, so I used those. I think it turned out well.
I used a similar opposites theme for the Dice puzzle, with an addition of 5 words to make it unique. I think not all words are necessary for uniqueness, but it solves pretty well this way.
The first Mastermind puzzle looks really nice, with a sequence of numbers and only white circles it solves really nicely. The second one was merely an attempt to construct a nice logical 5 digit puzzle.

I thought both Skyscrapers puzzles turned out nicely. The first puzzle uses three 4s and three 5s. The second puzzle has a trio of the same digit on each side. Of course I couldn't use four different digits as these are the only three digits you can have three of the same clue on the same side in this size.
I find it hard to theme Haido puzzles as the clues are a bit limited, but they both have nice logical paths.

The first time I saw an ABCD puzzle this way was at a Dutch championship. It was a bit of a surprise then. I wrote a similar puzzle for puzzlepicnic once and I thought it would be fun to include one for the championship. The ABCDE puzzle is a standard layout and I think it solves well.
The sum puzzles were a bit hard to work out openings at first as there are so many ways to reach the sums. So I went with obvious opening digits for both puzzles to then work back to more ambiguous digits towards the end. I think they both turned out well.

Puzzles can be found below.

UKPA Open Team Round: Hole in the Wall

It's been a long time since I actually posted something. I haven't really gotten around to writing puzzles for my blog in ages. I took a break for a while. I have been getting back to writing puzzles a bit, but those have mostly been going out to other places. Some of them might appear again on this blog and others might be seen in other places online.

This post will contain puzzles I wrote as a team round for the UKPA Open. It wasn't an official round. It was more t give the puzzlers some practise in team solving while the organisers finished the final checking. I haven't much idea on the results. I wrote the round in two days and sent it in to Liane two days before the Championship was held; just in time for them to get it ready to be solved. I didn't have time to get it tested, but I hope people still enjoyed it.

The structure of the round is pretty simple. There are six 6 by 6 puzzles and six 10 by 10 puzzles. You are not given the rules of each specific puzzle, but are instead provided with six sets of rules under which each puzzle could be solved. You have to match the puzzles to the rules, so that each rule is used once for each size. Additionally, all 10 by 10 puzzles have a marked 6x6 hole, in which the clues of one of the 6 by 6 puzzles have to be placed, without reflection or rotation. Each 6 by 6 grid can only be placed in one of the 10 by 10 grids. The rules for 6 by 6 puzzle won't necessarily match the rules for the 10 by 10 puzzle it is placed in.

Puzzles found below or through the following link.

Daily League Sudoku #44: Numpad Sudoku

Here is again a new variant, as far as I'm aware of. But if you really think about it, it's pretty similar to variants that have been used before. I think the tricky part is the fact that the horizontal and vertical rules aren't completely similar. The variant is based off the Numeric Keypad (or Numpad) you find on computer keyboards. On the off chance that someone is not familiar with its design, the given digits are in the design of one.
The puzzle has a narrow solve path through the opening, but finishes off pretty quickly towards the end. I hope it's enjoyable.

Rules for Sudoku

In this Sudoku a dot is given between 2 horizontally adjacent digits if they are horizontally adjacent on a Numeric Keypad. A dot is given between 2 vertically adjacent digits if they are vertically adjacent on a Numeric Keypad. All possible dots have been given.

Daily League Sudoku #43: Next To Nine Sudoku

Last Tuesday was the Dutch Sudoku Championship. I won the Dutch Championship and can now call myself Dutch Sudoku Champion for a year. The puzzles can be found at http://wcpn.nl. All Sudokus were written by Richard Stolk. In case you need the English translations for the instructions, they can be found in this forum post. This Sudoku was one of the types appearing the championship. I thought this was most likely the least common type to appear in the test, so that's why I decided to write one myself.
I think this puzzle isn't too hard, but I will await the times to see if my judgement is accurate. They are more often not correct when it comes to Sudokus. You can solve the puzzle at SudokuCup, which features all Daily League Sudokus suitable for the applet on a one day delay.

Rules for Sudoku

In this Sudoku, the digits on the outside indicate which digits are directly adjacent to the digit 9 in that row or column. The digits are not necessarily listed in order.

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Daily League Sudoku #42: Hit Sudoku

Last weekend was the Japanese NumberPlace Championship. It was full of great puzzles, but my favourite was the Hit NumberPlace by Naoki Inaba. I didn't manage to solve it during the championship as I didn't find the logic. But once I found the logic afterwards I really enjoyed it. That's why I decided to write one of my own for the league.

During the solve I realised a bit of logic that I thought would be fun to use in one of these puzzles. I just had to find a nice solution grid in which I could easily implement this. I actually stole a solution grid from the JNPC, which I slightly altered as at one point during construction I ran into no solution. But I noticed that by switching a few numbers around it could still have a solution. The trick I used isn't overly hard but I think it might be wise to try to solve the original puzzle first so that you can understand the logic involved, because I think it is useful to understand the genre before attempting this puzzle. The hit NumberPlace is #19 in the set.

That said, the puzzle is completely logically solvable. I think it is nice but it a bit on the harder side. Still, I hope you'll enjoy it.

Rules for Sudoku

Numbers outside the original grid indicate how many digits are the same in the solution grid in the corresponding row or column.

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Daily League Sudoku #41: Pusula

I haven't written any Sudokus in a while. Now that Tom Collyer is taking a break to focus all his attention on the upcoming World Sudoku Championships in the UK, I'm taking over the Friday together with Zoltan Horvath. We'll probably be alternating weeks, so that we both get our fair share of puzzles in.

I got this type off Serkan Yurekli's blog. I was browsing it for an example of a puzzle type and came across it. I thought it would be a nice idea for the Daily League. I hadn't ever made one. It wasn't too hard to write this type. I think in general many grids will allow a unique solution, but there's a few restrictions to the solution to make that viable. I wrote this one progressively and added the missing arrows in the end. I don't think it's necessary to follow the intended solving path as there's a general strategy to this puzzles that should also always work to solve them. I hope it's enjoyable. It shouldn't be overly hard as some of my other Sudokus have been.

Rules for Sudoku

In this Sudoku an arrow in a cell with an even digit points to the largest odd orthogonal neighbour of that cell. An arrow in a cell with an odd digit points to the largest even orthogonal neighbour of that cell. All arrows have been given.

Polish Puzzle Championships 2014: Team Round

This post will contain the puzzles I provided for the Team Round of the Polish Puzzle Championships. It wasn't an official round but a fun thing to do during the evening. Zoltan Horvath had contacted me if I had time to help working on a team round. as I had just finished my individual round, I figured I could. Zoltan came up with the idea of a Puzzle Labyrinth, where you needed to find your way through the labyrinth by solving puzzles and getting a clue to which would be a next puzzle. Eventually this evolved into a labyrinth where the puzzles were missing from the labyrinth and you had to place them back in the labyrinth. We decided to split the puzzles up into four categories, which would be marked in the empty labyrinth.
On Zoltan's suggestion we gave eachother 8 puzzle types, 2 per category, to write and we could choose one puzzle type ourselves. I gave Zoltan Tapa, Yajilin, Thermometers, Haido, LITS, Regional Akari, Yin Yang and Crossing Loop to write. He chose Lighthouses, First Seen Corral, Loop Extra and L-Dissection to write. He gave me Cave/Corral, Number Sea, Grades, Catloop, Retrograde Battleships, Star Battle, Masyu and Penta Blokus to write. I chose to write Kurotto, Laser, Tetromino Areas and Finnish Snake. Most puzzles had no restrictions, except that they shouldn't be too hard. Only the Circles puzzles had the restriction of being monocoloured. This was only a problem for Yin Yang and Masyu as those normally have multiple coloured circles. The Masyu worked pretty well, but Zoltan's Yin Yang topped that way more in difficulty to create. I was impressed with his puzzle. It was fun to solve. He wrote another harder one too.
When the puzzles were done we had to create a labyrinth. I first wrote one where each puzzle gives you one clue. But that labyrinth turned out too hard, so Zoltan rewrote the labyrinth with two clues per puzzle. This way it was easier to solve.
During competition most teams managed to solve the whole labyrinth, with the quickest doing it within 30 minutes.
You can find the Team Round in the following link.

Besides the Team Round, I will be also adding my harder labyrinth for those who like the challenge. You will have 3 options.
You can choose to solve this first file. [Edit: File updated 19-04-12014 5:25am blog time] It contains all puzzles with correct and incorrect clues. You'll need to solve the puzzles to figure out the correct clues and then use those correct clues to place all the puzzles in the grid.
You can choose to solve this second file. It contains all the correct clues only and no puzzles. It also contains a logical opening on page 3 and the solution on page 4. You can also use this after you get stuck on the first file or to check I didn't make a mistake when setting up the first file.
Lastly you can choose to ignore this challenge and just solve the puzzles or maybe solve the original Team Round with the easier clues.
It's up to you.

Puzzles can be found below. Sorry about the arrows, but didn't feel like redrawing the images for the blog.

Polish Puzzle Championships 2014: Individual Round

Last weekend were the Polish Sudoku and Puzzle Championships. The Championship was also open to International solvers this year. The playoffs would feature the best 4 solvers, while having at least two Polish solvers.
The Sudoku playoffs featured Tiit Vunk, Jakub Ondrousek, Jan Mrozowski and Krystian Swiderski. Jakub Ondrousek finish first in the playoffs, followed by Krystian Swiderski, Tiit Vunk and Jan Mrozowski, making Krystian Swiderski the new Polish Sudoku champion. Full results can be found here.
The Puzzle playoffs featured Przemysław Dębiak, Matus Demiger, Zoltan Horvath and Tomasz Stróżak. The final results remained almost the same with Przemyslaw Dębiak finishing first, followed by Zoltan Horvath, Matus Demiger and Tomasz Stróżak. Full results can be found here.

I contributed a set for the Puzzle Championships for the individual round and wrote a team round together with Zoltan Horvath.

You can find all puzzles of the Championships in the following link: Sudoku Rounds + Team Round, Puzzle Rounds. My puzzle set is round 4. This post will feature all the puzzles from my individual round. Tomorrow I will post the Team round puzzles with a special surprise.

Last year's set was a bit on the difficult side, so I tried to think of a way to rectify that this year. I decided to write 2 puzzles per type, one smaller/easier one and a larger/harder one. I didn't want to make any too difficult. I selected 10 varying types of puzzles. I was hoping to average about 1.5 minutes per puzzle on the smaller ones and about 4.5 minutes per puzzle on the larger ones. I had the set tested by Prasanna Seshadri, James McGowan and Stefan Gaspar. The smaller puzzles made that average pretty well, but the larger puzzles were more inching towards 5-5.5 average and all of them had some outliers. I couldn't really decide well which puzzles to cut so I sent in the whole set and let them know that they could leave out a puzzle type if necessary. During their testing 3 of the larger puzzles seem to have cause some problems as they went up in score. I think the set will have worked well none-the-less for all solvers with the easier puzzles to work with as well, but I'd love to hear some feedback form those who were there.

Puzzles can be found below.

Puzzle #167: Araf, Nurikabe, Capsules, Catloop

Last weekend were the Polish Sudoku and Puzzle Championships. I wrote a set of puzzles for the championships and helped create a team round with Zoltan Horvath. Today I will be posting the puzzles that didn't make it to the championships. Most of them were too hard for their intended purposes. I will also be posting the puzzles that appeared on the championships later this week.
Three of the puzzle types were from the individual rounds and one is from the team rounds.

The Araf puzzles were the first ones I had written of this type. I still had to get used to construction a bit. When I do that I tend to make the puzzles a bit harder, just to see what's possible. The smaller one isn't too hard, but still a bit harder than intended.
The Nurikabe puzzle isn't actually very hard, but I changed it as I saw an aesthetically nicer version of this puzzle. That one was also a bit easier than this puzzle, which I didn't mind.
The Capsules puzzle was really too hard. It was the first puzzle I'd written for the championships and I hadn't totally finalised my intentions then and thus went a bit overboard on difficulty.
The Catloop puzzle was written for the team round. It is a silly name play on the Catwalk puzzles, which was again a renaming of the Meander puzzle type to give a fun visual theming on the website. I think this type is also known under many other names. The first puzzle is an easy puzzle, while the second is a hard puzzle. I had written the second one first and after feed back written two easier puzzles. One of them went to the team round and the other one was left over. I think this was actually the easier of the two puzzles.

Puzzles can be found below.

Rules: Catloop

Draw a single closed loop through the grid by connecting the centres of cells horizontally and vertically. Numbers on the outside indicate how many cells are used by the loop in that row or column.

This puzzle is a variant on Catwalk. In this puzzle type you draw a path from the given beginning and end point instead of a loop.

Rules: Araf

Divide the grid into some regions, formed by orthogonally adjacent squares. Each region should contain exactly two given numbers. The size of each region should be a value (in unit squares) strictly between the two numbers inside that region. Its size can't be equal to either of the numbers in the region.

14th 24 Hour Puzzle Championship

This year I wrote a set of puzzles together with Hns Eendebak. I was a bit tight on time with a holiday and other championships that I wasn't sure if I'd be able to write everything in time. I still ran a bit late getting everything together but it was in time for the championship.
This year's championship was won by Peter Hudak. Nikola Zivanovic and Zoltan Horvath finished second and third.
There were 30 competitors total in this year's championship, of which 29 did our set. The set was a bit on the long side this year with the Michael Mosshammer from Austria being the top scorer with 695 points. It would have been better if the top scorer had about 100-150 points more. The set contained 24 puzzles in total, so I should have probably cut 2 puzzles in the end.
In this post I will be adding all the puzzles I wrote. You can find the complete set and all other sets here. If you need to see the instruction booklets for any of the set you can find them in this forum post.

Puzzles can be found below.

Puzzle #166: Domino Extra

The last puzzle are two Domino Extra puzzles. I'd written two at the start, but they ended up testing too hard. So I wrote a third one that was much easier than these ones to be included in the WPC set. They have a similar opening, but should both still be fun to solve.

Rules:

Divide the grid along the grid lines so that each given pair of numbers appears in exactly one shape.

 

Puzzle #165: Blind Spot

Today the second puzzle that wasn't used in the WPC. This is a Blind Spot puzzle. It's actually a size smaller than the puzzle used at the WPC, which was 7x7. But I actually think this was the harder of the two puzzles. That's why the larger puzzle was used in the WPC. I like writing these puzzles, but I think they can be tricky to solve as the logic is a bit unfamiliar compared to other Latin square type puzzles.

Rules for Blind Spot

Puzzle #164: Gemini Loop

I was going through my puzzle files and realised I had a few unused puzzles that I had written for the WPC 2013. One of each type was used, but for certain types I'd written a few just to have a choice depending on how they tested. I had posted two sets of puzzles before, that I had originally written for the WPC, but these puzzle types were rejected. These puzzles were the following Yajilin and Pentopia puzzles.
Today's puzzle is a Gemini Loop puzzle. I think it's a nice puzzle but I selected the other one for the WPC as I thought that one solved a bit nicer.

Rules:

Draw a single closed loop through all squares in the grid by connecting them horizontally and
vertically. The loop doesn't touch or cross itself. Cells with the same letter all have the same
appearance as to how the loop passes through it. Cells with different letters have a different appearance.

Puzzle Competitions: ZeKa 2014

Last weekend was the ZeKa competition in Croatia. It featured both a individual and a team competition this year. The individual competition was won by Goran Vodopija; Marko Obradović and Dragan Tolomanoski finished second and third respectively . The team competition was won by Dragan Tolomanoski, Bojana Vojnović and Vanja Fornazar.
I provided one of the Team rounds this time. The theme of the round was Imposters. The round consisted of four classic puzzle types. Each type had 4 puzzles, where one of the puzzles was an Imposter. It wasn't actually solvable as that puzzle type, but was solvable under a different set of rules. The rules of this puzzle was provided. The imposters weren't designed to be logically deduced, but purely intended to break down under the original rules.
The four puzzle types were LITS, with Double Back as imposter; Shikaku, with Corral as imposter; Skyscrapers with Haido as imposter; Slitherlink, with Turning Fences as imposter. Two of these combinations have appeared on my blog as a Double Trouble puzzle. One of them appeared as such on Grant Fikes' blog. The other is probably possible as a Double Trouble puzzle, but haven't tried that yet.

Puzzles can be found below or in the following PDF.

Rules: Shikaku

Divide the grid in a number of non-overlapping rectangles along the grid lines. Numbers in the grid indicate the size of the rectangle they are in. No rectangle can contain more than one number.

 

 

Puzzle #163: Turning Fences

The LMI Marathon puzzle that was solved during the competition was actually the second version. In the first version I put in some stuff that came naturally to me for this genre, but stumped the test solvers. That's why there was an easier second version, which still took a relatively long time for the test solvers. That was why I added the Tutorial on my blog, just so people would realise the basics that I had figured out when designing these puzzles.
Here is the first puzzle I wrote. There are a few similarities to the second puzzle as I kept the bits that were solved quickly in the first test solve in the puzzle. It has the same layout as the second puzzle. For those who hadn't figured out the layout, the givens are in the shape of 25 letters that spell out TURNING FENCES LMI MARATHON 3 in an inward clockwise spiral. The 3 shape is made up completely of 3's.

Enjoy, but take some time to get through it logically.

Rules for Turning Fences

Click to enlarge

Tutorial: Turning Fences

This week the LMI Puzzle Marathon will start. It will run from February 21st till March 2nd. For this event I have written a Turning Fences puzzle. To prepare people a bit for a more unknown genre, I will write a tutorial about the logic behind the genre. It won't be complete, but it should be enough to tackle the upcoming puzzle. In the next days there will also be a few practise puzzles. You can also practise some of the puzzles already on my blog, but most of these are logically harder than the puzzle in the actual test. For those who happen to own Akil Oyunlari Issue #75, there are also 4 of these puzzles by my hand in there. They are logically a bit more friendly.

Tutorial below.

Daily League Sudoku #40: Inside Skyscraper Sudoku

Today's puzzle is a Skyscraper Sudoku variant. This is a more Logic Puzzle variant of Sudoku. I normally would represent this as a Regional variant of Skyscraper puzzles. The Sudoku part doesn't often come forward as much as the Skyscraper part during the solve. But as I always like Skyscraper Sudokus, I figured I'd make one too. This variant sometimes has all possible arrows given, but I prefer it without this rule. A lot of the smaller numbers end up being unnecessarily given an arrow there, although the negative information is also fun to use. I just prefer it this way.
I had set up this opening a few weeks ago, but I was not able to finish the puzzle successfully. After a few more tries, I came up with this puzzle. I was originally intending to make the clue arrangement symmetric, but as you can't just put a clue everywhere that caused some problems. This was the point where the puzzle ended up being unique. I liked the way it solved at the end, with a somewhat tricky step to finish the puzzle. So that's why I settled for this one. I had a little trouble finding a satisfying layout, but I think this one should do. If someone has a suggestion that could work better, I might change the image. Having said that, enjoy the puzzle.

Rules for Sudoku

In this Sudoku each digit indicates the height of a Skyscraper. Digits in cells with arrows indicate the number of buildings that can be seen in the direction of the arrow from that cell. Taller buildings block the view of smaller buildings.

Daily League Sudoku #39: Palindrome Killer Sudoku

Today's Sudoku is themed around today's date. As the date is a palindrome, the choice of Sudoku was easy. I chose for the combination with Killer Sudoku as I could use 21 and 12 easily in that variant.
The puzzle has a somewhat complicated opening. But I hope that people will understand where to look considering the choice of combined variants. If not, I guess there's very little to get in this one. But when the opening's finished, the solve should solve without much problems.I'm still happy with the Sudoku overall. I think the 21/12 layout of cages looks really nice and the way the palindrome resolves the obvious non-uniqueness worked out really well. I hope people will feel the same. Enjoy.

Rules for Sudoku

Instead of given numbers, you now have a few dashed cages. The number in a cage indicates the sum of the digits in the cage. Digits can't be repeated in any dashed cage. Additionally, digits along a grey line must form a palindromic sequence.

Click to enlarge

Daily League Sudoku #38: Parity Count Sudoku

This week's Sudoku is an Odd/Even Sudoku variant. I'm pretty sure I have seen this idea before. I have no idea where or what is was called then. So I just gave it my own name.
I always like Sudokus that use parity constraints, which require you to basically build an Odd/Even Sudoku. I made a puzzle that required this before, namely my Battenburg Sudoku. In this one you actually have to solve the Sudoku to set up the whole Odd/Even Sudoku grid. I think because of the interaction between Sudoku and parity rule, this idea is a bit more interesting. I don't think the puzzle is overly difficult. The opening shouldn't be too hard, but there's a few sticking points in the middle in figuring out which numbers go in certain grey cells. I had fun designing it. I sacrificed symmetry a bit as the left top square being grey helped make it unique and I preferred that over giving extra givens. I hope people enjoy it.

Rules for Sudoku

In this Sudoku digits in grey cells indicate how many digits of the opposite parity appear in the cells touching it.

Daily League Sudoku #37: Non-Consecutive Sudoku

This week again something familiar. I had a different puzzle ready, but I sadly realised my intended opening made no sense. I had adjusted two digits, which I thought didn't affect the opening, but on a resolve I realised they did. I will give that one another go later, but I didn't really have the time to fix it today. So instead here is a Non-Consecutive Sudoku.
I always enjoy solving Non-Consecutive Sudokus. I think writing them is a lot trickier though. I think it doesn't really suit the way I like to write Sudokus or puzzles in general. I think the puzzle solves nicely, but it won't be one of my more memorable Sudokus. But as I promised a more easy Sudoku this week, I think this one will at least keep that promise. Enjoy :).

Rules for Sudoku

In this Sudoku consecutive digits can't be orthogonally adjacent.

Daily League Sudoku #36: Sum Relations Sudoku

I have seen puzzles similar to this before, except in a Killer Sudoku format. In those puzzles the relations are given between different cages. Here the relation is between the sums of adjacent cells on either side of the symbol.
This is again a harder puzzle. I don't know exactly how hard it is, but there's definitely no progress to be made if you don't understand the opening. I wasn't expecting to be able to make this variant without any givens. But I managed to create an opening that works without any givens. I think it's a nice and interesting opening. The middle is probably a bit easier, but I think the end is again a little bit harder, but worked out nicely in my opinion. I'll think about making something easier again next week, but I can't exactly promise that. When I find an interesting opening, I just run with it. And interesting is generally hard. Enjoy this puzzle though.

Rules for Sudoku

In this Sudoku, the symbols indicate the relation between the sums of the 2 cells on either side of the symbol.

Daily League Sudoku #35: Rank Killer Sudoku

This week a puzzle type taken from Richard Stolk's V2V test at Logicmasters India. I had planned on posting this type earlier, but my attempts at making one never got anything useful. So I made other puzzle types instead, that worked out easier. But this one seemed to work well.
This puzzle is again a harder one. I had posted a few easier ones in the last few weeks. This type has again some room for me to be a bit more creative with the opening. There's a few steps that combine Killer Sudoku and Rank Sudoku to start this one off. They are still all logical steps, but it takes a bit more effort to figure them out. I still think it is an enjoyable puzzle.

As a reminder all Daily League puzzles are also solvable at SudokuCup.

Rules for Sudoku

The sum of digits inside each dashed cage is given at the upper left cell of the cage. A digit 'N' in a circle means that the digit in the cell is the Nth smallest number in the corresponding cage. Digits cannot repeat within a cage.

Click to enlarge

Daily League #34: Arrow Sudoku

This week a more familiar variant. Arrow Sudoku has been around for a while now and there's been many nice puzzles made. I hope this one is also enjoyable.
I decided to go for a similar layout as my Renban Sudoku I made a while back for the league. I thought it would work well with Arrow Sudoku too. I was able to give fewer givens though as the arrow already forces some placement because of the direction. I shortly considered making a directionless Arrow Sudoku, where the circle could be at either end, but this layout wasn't very friendly for that variant. At first I had a harder variant of this Sudoku, but it took me too long to solve it myself while knowing the openings because the middle and end ran a lot on very complex interactions between the arrows that I really couldn't justify logically. So I revamped it a little to make it more solvable. The harder opening is still in this puzzle but it is no longer needed to solve the puzzle as there's a more friendly path through the puzzle.

Rules for Sudoku

In this Sudoku a number of arrows are given with a circle at the end. The digit in a circle is equal to the sum of the digits along its arrow. Digits may repeat along an arrow as long as they don't break any Sudoku rules.

Daily League Sudoku #33: Hi-Lo Product Frame Sudoku

This week another variation on the Hi-Lo Frame Sudoku. It's a fun variant you can always play around with. This time it's products instead of sums. It leaves for fewer options and thus allows fewer clues.
Outside clues and empty grids are always my favourite Sudokus to construct. It's generally a bit of a struggle to get them to turn out unique or even create an opening. This one was a bit of a struggle to get unique as my final clue had to settle about 35 cells. There were a few options that got pretty close but would end up having no solution. This was the only one I could find that settled the uniqueness issue. There was a second option that I thought had worked, but then I realised the clue didn't actually have to be in that configuration and thus there were many more solutions. The puzzle itself is not overly hard as the clues give you a lot of information from the start and the clue I used for uniqueness is already helpful far earlier than it was in my construction.

Rules for Sudoku

In this Sudoku, the numbers on the outside indicate the product of the highest and lowest digit in the first three cells of that row or column when looking from that side.

Daily League Sudoku #32: N-Sums Sudoku and Quad Max Difference Sudoku

This post is just preceding this week's Sudoku. I hadn't made blogposts of my previous 2 Sudoku. The first one was made en route to Beijing for the WSC/WPC. I had no access to Facebook or BlogSpot there, so I wasn't able to make any posts. The second one I was not at home and managed to sneak in some time to make a quick Facebook post with the image, which all is a little bit faster than making posts on my blog.
The first puzzle is a variant on the X-Sums Sudoku, of which I have made a few. The variant is a bit more limiting as now not every row and column necessarily has a valid clue. This is caused by the fact that a number N has to appear in position N to become a valid clue. The construction took a while as I wanted to keep the symmetric layout and sometimes I wasn't able to make the layout symmetric as there was no longer a clue available. There are a few clues that aren't necessary for uniqueness in this puzzle, but they don't hinder the solving path and make it overall a little bit easier. I think people don't mind that my Sudokus are made a bit easier in general.
The second puzzle is a simple variant with differences. It has more given numbers than I would have wanted, but it wouldn't be unique otherwise. I wanted to make a puzzle which had a single instance of every possible Quad Difference clue possible. This of course forced one of the clues to be in a specific position as otherwise there's be no unique solution available. Which is why I went for this layout. I don't think this one is overly hard. There's a few key points in the solve where you have to use the right clues.

Rules for Sudoku

N-Sums Sudoku:
Clues outside the grid indicate the sum of the first N digits seen in that row or column from that side. The digit N is always indicated by the Nth digit seen from that side. In other words, it is always the last digit in the summed set of digits.

Quad Max Difference Sudoku:
In this Sudoku, numbers on grid points indicate the maximum difference between the four digits surrounding it. Each difference must appear at least once around each clue.