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.