Double Trouble #8: Skyscrapers and Haido

Haido is a puzzle type that I've recently come across a few times again. It showed up in a recent Skyscrapers contest hosted on Logic Masters Deutschland and the latest Akil Oyunlari magazine. All puzzles I've recently solved were really nice. So I tried making a few and found them more interesting to make than I at first thought they would be. When I saw the results, I thought they all look exactly like normal Skyscrapers puzzles. But they never solve uniquely as a skyscrapers puzzle. Usually they don't even have a valid solution.
So this led me to try to design one that worked as both. I found it hard to find an opening that worked nicely for both. so I cheated a bit with introducing a 6 clue for the skyscrapers puzzle, which is meaningless in the Haido puzzle. I like how they both turned out, although they are challenging.

Rules for Skyscrapers

Rules for Haido

Firstly this puzzle can be solved as a regular Skyscrapers puzzle. This is a hard puzzle.

Secondly it can be solved as a Haido puzzle. It is harder than the skyscrapers puzzle. I haven't solved any that are this difficult.

Rules: Haido

Haido is a genre based on the Skyscrapers genre.

Place the digits in the given range once in every row and column. The digits represent skyscrapers of that height. The clues on the outside indicate that the building of this height is visible in that row or column from that side. Larger skyscrapers block the view of smaller ones.

The example uses the digits 1-4.

Puzzle #130: Pentomino Areas

Pentomino puzzles I have slowly grown into. When I first started puzzling, I always had a lot of trouble solving them. In my early Breinbrekers issues, pentomino were the ones that were most often left unsolved. I prefer the placement type pentomino puzzles over the packing type. I've never been very good at packing problems. I've gotten more proficient at pentomino puzzles over time and now usually enjoy them.
Pentomino puzzles were the first type I regularly contributed to Breinbrekers, where I would write 18x18 Battleship-like puzzles, which used all Pentominos twice. I haven't written them in a while though. They take a while to get unique and solvable.
This pentomino type will appear in the upcoming LMI-test Borders & Beyond written by Prasanna Seshadri, which I was a test solver for. The type can sometimes get me stuck badly. The last time that happened was at the Dutch Puzzle Championship in '06, when it was featured in the semifinals and I couldn't get it done and ended up guessing my way through. Luckily I could catch up on the second puzzle and still qualify for the finals then.
This puzzle has a feature I like to use in puzzle types as all areas are the same size, which isn't common in this puzzle type. I have done the same in LITS as well, although there it was only on an 7x7 and 8x8 size.

Rules:

Place all 12 pentominos once in the grid so they don't touch eachother, not even diagonally. Each blackbordered area contains one pentomino.

Click to enlarge

Puzzle #129: Contact

I've given this genre another go. I think the 1 through 7 theme worked out pretty nicely. The opening of the puzzle is easy, but it gets a bit harder towards the end.
For everyone who's been trying to get to this post yesterday from other blogs, I'm sorry. I accidentally forgot to add the scheduled time.

Rules for Contact

Puzzle #128: Expanded Sudoku

I have played around with this idea a bit already before. When it popped up in the US Sudoku Qualifiers under the name Sudoku stairscases, I figured I'd give it another go. I prefer Expanded Sudoku as Sudoku Staircases really only work for one layout. I made the first ones back in early 2010. There'd been other Sudokus with gaps in rows, but I hadn't seen them with the standard 3x3 blocks. My first puzzles are puzzle #1695 and #1703 on PuzzlePicnic. Later on I tried to make them with irregular cages too, namely puzzle #2584 and #2607. The logic in them isn't any harder than any normal Sudoku, but I still think the increased size adds a bit of an extra challenge.
This puzzle isn't any harder than the other puzzle. I like how it looks though. This puzzle has one more challenging step that stayed in the puzzle while maintaining uniqueness.

Rules for Sudoku

In this puzzle the rows and columns continue over empty space.

Puzzle #127: Easy as ABC; Regional

With this puzzle it is back to old school puzzling for me. Easy as ABC puzzles are one of the first puzzle types I solved. They used to appear as an extra puzzle in Logiquiz magazine. These were my real introduction to logic puzzling. This was before I started buying Breinbrekers. They appeared under the name Letterraam, which is a name for an old tool to help kids learn to read in Dutch. Without these puzzles I would have probably never bought Breinbrekers.
These puzzles uses two common variations on the genre. Firstly they don't use the standard "first seen" clues, but indicate the position of the letter when looking from that side. So A3 means that A is the third letter when looking from that side. This variation makes constructing larger grids much easier as large grids tend to get uniqueness problems in the centre, where your clues don't have any effect. Secondly they have regions that function just like a Sudoku. This helps reduce the number of clues necessary to make it unique.

Rules for Easy as ABC

Fill the letters A~E (A~G in the larger puzzle) once in every row, column and black bordered region. Otherwise follow Easy as ABC rules.

Medium Puzzle

  

Hard Puzzle

Click to enlarge

 

Puzzle #126: Tapa; Mastermind: Tapa/Knapp Daneben Tapa

At first I was trying to make a Knapp Daneben Tapa that looks exactly like a normal Tapa. That wasn't as easy as I hoped it would be. So I changed my approach and added the Mastermind component to it. This made it far easier to construct. The puzzle itself is pretty tough though.

Rules for Tapa

Tapa Mastermind:

The gray numbers between corresponding rows represent Mastermind clues. The numbers indicate how many squares in the same position are coloured in both grids.

Knapp Daneben Tapa:

Follow regular Tapa rules. Additionally all given digits are wrong. They are all either 1 higher or 1 lower than the given value. This means a 1 can possibly turn into a 0.

Click to enlarge

Puzzle #125: Ripple Effect

Here's another Ripple Effect puzzle. It's been a while since I posted one. this is mostly caused by the fact that I've been writing Ripple Effect puzzles for Breinbrekers as well. It's not always easy to find good openings for clueless grids. It also helps to not make any errors. The construction took a while as I had made a mistake very early on and didn't notice after finishing the puzzle on my fifth try. Took me another four attempts to fix that mistake correctly. But in the end I think the puzzle worked out well. I have used a similar opening before. It's moderately hard, as most my Ripple Effect puzzles are.

Rules for Ripple Effect

Puzzle #124: Doppelblock

I'm back again to posting. Hopefully for a while. The Olympics were the main contributing factor to me not posting. I spend most my free time watching the Olympics. I didn't really find the time to create puzzles then.

Today we have three Doppelblock puzzles. It's originally from Naoki Inaba, I'm going with the German name from crocopuzzle. Simple name, but it sounds nice. Serkan Yurekli gave it an English name in Smashed Sums, but I didn't particularly like that name.
When I first saw this genre on crocopuzzle, I liked it. Although crocopuzzle regularly has this small minimal puzzle that is a bit annoying to solve as it's too had to discover the logical path. The larger ones are always nicer, but tend to have givens in the middle. This makes them a bit less elegant to me. It feels a bit similar as givens in skyscraper grids.
I think the puzzles worked out well. Nothing too difficult, but something to keep you busy for a little while. This puzzle type will also appear in the UK Puzzle Championship over the upcoming weekend, so it will be nice practise in this genre for those competing. It was merely a coincidence though. I had made these puzzles before the instruction booklet came out.

Rules for Doppelblock

Easy Puzzle

Medium Puzzle

Hard Puzzle

Rules: Doppelblock

This genre was developed by Naoki Inaba,

Colour 2 squares black in every row and column. Fill the remaining white squares with the digits 1~N, so that each digit appears once in every row and column. N equals the size of the grid minus 2 (e.g. for the example N = 3). The numbers on the outside indicate the sum of the digits in between the 2 black squares in that row or column.

Puzzle #123: Parquet

Here's again one of Naoki Inaba's genres. It has some similarities to the Windows genre, which featured in the WPC, which can also be found on Naoki Inaba's website. It's known as conect on his website, but I don´t find that a very nice name. I changed it to Parquet as the grids reminded me of the Parquet Sudokus.
The puzzle worked out really nicely in my opinion, utilising all rules as well as possible on a 10x10 grid.

Rules for Parquet

Rules: Parquet

This genre was developed by Naoki Inaba.

Colour one of two regions in every blackbordered 2x2 area to form a single contiguous shape. This shape doesn't have any 2x2 coloured sections anywhere. Also this shape doesn't form any loops anywhere.

LMI Practise : Logirace

A recent comment on my blog mentioned how Loop genres feature prominently on my blog. It's somewhat true as I am better at finding interesting things to do with loop genres. This weekend happens to be a puzzle test on Logic Master India named Logirace. This test features nothing but loop genres. Half of them are Nikoli Loop genres(Corral, Country Road, Masyu, Slitherlink and Yajilin), 3 less familiar genres (Dutch Loop, Tapa Loop and Dotted Loop) and 2 that are new to me(Border Loop and Comet). I figured I'd try to make a few examples of the less familiar ones. Some puzzles worked out better than others. I didn't like working with some of the genres so much. Hard to get them unique and nice. Especially the Comet and Dotted Loop have issues of there being a unique solution a lot in construction. But I think each puzzle will help a bit in preparing for the test, if that's what you're interested in. Otherwise just solve them for fun. It's what puzzling is really about.


You can find the puzzle below. If you want to see smaller examples, check the instruction booklet.

Puzzle #122: Shakashaka

I haven't seen how the Nikoli puzzles of this genre tend to look like, but I expect mine are a bit different. I prefer to keep the amount of clues as low as possible and make the open areas resolve themselves. I figure my puzzles tend to be on the harder side because of that. I like how it turned out. I was planning on doing a 1-2 antisymmetric clue pattern, except the 3 forced itself and I liked how the puzzle went till that point. So this is how it ended up.

Rules for Shakashaka

Puzzle #121: Heyawake; Symmetry

I had first seen this variant on Mathgrant's blog. I thought it worked nicely. So I figured I'd give it a go too. It wasn't the easiest to start as Symmetry is always a weakness for me when solving. It doesn't really register with me too well, usually. But then I got the idea to bring back the Antisymmetry label, which I had added to Puzzle #1, but hadn't used since. I always like to build in some kind of antisymmetry in the givens of my puzzles, except it somehow had never come back in any of my puzzles for my blog. So for this puzzle rotationally symmetrical cages with clues have the opposite clues given. This doesn't hold for cages without givens. It would have been cool if it did, but I think that would be awfully difficult to accomplish.
I think the puzzle worked out in the end. The one cell pairs were to fix uniqueness issues, which didn't really bother the solving path. Enjoy.

Rules for Heyawake

Follow normal Heyawake rules. Additionally, this puzzle has no numbers as clues. Instead the clues indicate if a room has 180 degree rotational symmetry or not. An S indicates that the room has 180 degree rotational symmetry. An A indicates that the room does not have 180 degree rotational symmetry.

Puzzle #120: Line of Sight

I still enjoy making these puzzles. It's not the easiest to create openings, so they end up somewhat similar. But once you get going, it's really fun to play around with. This puzzle is of medium difficulty. I've made a few harder ones, but still some trickier points.

Rules for Line of Sight

Puzzle #119: Magnets; Construction

I've said before I liked Magnets puzzles. So I've tried to experiment with them a bit. The Tapa inclusion worked really nicely. For this one I went another way.
I came across the Tateyoko puzzle on Naoki Inaba's website. Here the goal is to divide the grid into Domino regions. An O on a border indicates that the lengths of the sides touching there are the same length. An X on a border indicates that the lengths of the sides touching there are of a different length. I then realised, basically you are building Magnets puzzle grids. So I figured it would be worth trying to combine them.
I first started with a 10x10 grid and found a bit of a start. But I realised this way it would turn out far too hard. So I scaled it down to an 8x8 puzzle. It's still not particularly easy, but it's more doable than the 10x10 opening. I'd advice getting some practise with the Tateyoko part of the puzzle by going to the link given above.

Rules for Magnets

Follow normal Magnets rules. Additionally in this puzzle, the domino regions in which the magnets go aren't given yet. Instead you have to construct them. Some borders between domino regions are already given. If there is an O on a border, it indicates the lengths of the sides touching there are of equal length. If there's an X on a border, it indicates the lengths of the sides touching there are of unequal length.

Rules: Magnets

The grid is divided into domino regions. Place some magnets into these regions. Each magnet consists of a + pole and a - pole. Equal poles aren't allowed to touch by a side. The numbers on the outside indicate how many of each symbol are located in that row or column.

Puzzle #118: Pentopia

This is the first 12x12 Pentopia puzzle I've made that only has 10 clues. Most of my puzzles have 12 given clues. That just seems the total that's mostly needed to make the puzzle unique. Just like that most my 10x10 Yajilin puzzles use 10 clues. The opening to this puzzle is tricky, but after that it shouldn't cause too many problems.

Rules for Pentopia

Click to enlarge

Puzzle #117: Masyu; In and Out

There's been a few Masyu variants done with optional Black and White circles. Here's another one, with a extra twist. The twist is taken from the Castle Wall genre. I think the puzzle worked out nicely. The optional quality makes the puzzle a bit trickier. Maybe the next time I'd make the puzzle a bit bigger, to make the twist play out more.
I know I've been making more variants the last few weeks. That's why I've added an extra tag for all puzzle variants and hybrids to find them easier on the blog. I've left the variant tag off the Sudokus as every Sudoku is a Sudoku variant. If people think I should also add it to them, I will.

Rules for Masyu

Follow normal Masyu rules. Additionally, not every black and white circle has to be visited by the loop. If a black circle isn't visited, it will be located outside the loop. If a white circle isn't visited, it will be located inside the loop.

Rules: Masyu

This genre was developed by Nikoli.

Draw a single closed loop connecting the centres of cells horizontally and vertically. The loop
doesn't touch or cross itself anywhere. The loop runs through all black and white circles. The loop
turns in every black circle and goes straight through both adjacent squares. The loop goes straight
through every white circle and turns in at least one of both adjacent squares.

Puzzle #116: Tapa; Borderline

This a variant I thought of myself. I checked the TVC booklet and it didn't appear in it. So as far as I know it's original. It is a simple variant that I had attempted before. I couldn't make it work then. I think I wanted to make it too difficult then and couldn't get it to work. This one worked out. It's still tricky though. This one has all clues on a border between 2 cells. I do think it's just as easily possible to put the clues on nodes between four cells. I figured having to choose between 2 cells for the first one is difficult enough.

Rules for Tapa

Use standard Tapa rules. Additionally, each Tapa clue is located on a border between multiple cells. This Tapa clue belongs in one of these cells. Determine which cell the clue belongs in and solve the puzzle.

Puzzle #115: Regional Akari

I've never really been a fan of Akari puzzles. The easy ones I find just go too quickly to really enjoy. The harder ones I feel like I'm just using trial and error. That's mostly why I haven't really made many of them. When I saw the regional variant on Naoki Inaba's site, I figured I'd give this a try in construction. I think it turned out okay. Nothing too difficult.

Rules for Regional Akari

Rules: Regional Akari

This genre was developed by Naoki Inaba.

Place one lightbulb in each blackbordered region, so that every cell in the grid is illuminated by at least one lightbulb. Lightbulbs illuminate all cells they can see in a horizontal and vertical direction. Black cells block their sight. No two lightbulbs can illuminate eachother.

Double Trouble #7: Liar Loop and Maxi Loop

I guess this twin isn't very surprising. I did create the Liar Loop genre from the Maxi Loop genre. It has been the hardest one to acchieve so far though. I had attempted this a few times already, but it always lead nowhere. For this one I finally found a solid opening, that lead to good progress in both genres. Finishing it succesfully took some effort though. The puzzles both turned out well and I like the way clues keep helping in both genres.

Rules for Liar Loop

Rules for Maxi Loop

This puzzle can be solve as a Liar Loop puzzle. This one is the harder of the two puzzles. But that's mostly because Liar Loop is inheritently hard. It's a bit of a challenge to create really easy ones.
This puzzle can also be solved as a Maxi Loop puzzle. It's a bit easier than the Liar Loop puzzle. Main reason for this, is that I couldn't avoid using 1 clues for the Liar Loop puzzle.

Puzzle #114: Corral; Crates

I liked the Crates variation when I first saw it on Palmer's blog. I didn't like the red numbers so much though. That's why I preferred the one puzzle without red numbers. Last year's USPC also featured a Corral Crates puzzle without red numbers. So my puzzle also doesn't contain any red numbers.
This puzzle originally didn't start out as a crates puzzle, except the five 17s and the antisymmetric pairs of 7's and 10's on the outside made a valid corral loop very difficutl to acchieve. I constantly ran into the problem of having no possible valid loop when designing. So I tried to switch to a Corral Crates design instead. It did make the opening a bit harder. I edited out a harder spot in the middle, but kept the opening in as I had already found it a nice way to make the five 17s work in earlier design attempts.

Rules for Corral

In this puzzle there can be isolated loops on the inside the bigger loop. These isolated sections always form a 1x1 square. Different loops don't touch eachother, not ever by a corner. These isolated loops block the sight of the numbers.

Click to enlarge

Puzzle #113: Easy as Japanese Sums

I encountered this puzzle type the first time when test solving Serkan Yurekli's puzzle set for last year's 24 hour puzzle championship. I really liked them, although they caused more trouble than you'd expect for their size. Even though the puzzle idea is very similar to Japanese Sums puzzles, the Latin Square component in this genre makes solving a lot different though. Only later I found that the genre also existed on Naoki Inaba's website.
This is the first time I tried to create one myself. I like how it turned out. It's moderately difficult.

Rules for Easy as Japanese Sums

This puzzle uses the digits 1-5.

Rules: Easy as Japanese Sums

This genre was invented by Naoki Inaba

Place the digits in the given range once in every row and column. The numbers on the outside indicate the sum of the first digits seen from that side till encountering an empty square.
The example uses the digits 1-3.

European Championship Football

A while back at a Dutch championship we had a round inspired by the World Football Championship that had started that weekend, so I've written a few puzzles using the teams in each group. They're not very hard. One of them is a simple score deduction puzzle. The standings are purely fictional, nothing intended. The second is a logic puzzle, which includes the game scores. I hope you like my awesome drawing. The third is a path puzzle using the country names. The fourth is a Four Snails puzzle using the country names.

Group A: Final standings

Part of the final standings of group A are given. Fill out the rest and deduce the match results. For those not knowledgable of football, a win gives you 3 points, a tie gives you 1 point, a loss gives you 0 points.
G = Matches played, W = Matches won, T = Matches tied, L = Matches lost, P = points score, GF = Goals scored, GA = Goals conceded.

Click to enlarge

Group B: Logiquiz

Sunday 17th of June, 20:45. A Dutchman, German, Portugese and Dane have come together to watch their group's final matches. They're each wearing their countries shirt with a different number. They also brought another item to dress themselves up. Figure out who sat where, what number they had and what item they brought.
All clues are given in chronological order.

Click to enlarge

Group C: Country path

Draw a path from the first letter to the last letter of each country in order. The path doesn't rouch or cross itself. Different paths can't touch or cross eachother, except in a cell with a letter. If two paths both go through a cell with a letter they have to both go straight through it.

Click to enlarge

Group D: Four Snails

Write all countries in one of the four spirals. Write the letters in order from the opening inwards. No letter may repeat in any row or column.

Puzzle #112: LITS; Inversed

Today's puzzle is a variant on the LITS genre. I don't remember seeing it before. Constructing it went smoothly, although there were some points at the end where it caused trouble to keep it unique. Hope you all like it.

Rules for LITS

Colour some squares to form a single contiguous wall. The wall has no 2x2 coloured areas anywhere. In each blackbordered region a shape of 4 orthogonally connected squares remains empty. Identical shapes in different regions can't touch eachother by a side. Rotations and reflections are considered the same shape.

Croatian Puzzle Set

I had been asked to write a puzzle set for a competition in Zagreb last weekend. I wrote a set of puzzles which was a mix of Dutch and Japanese, familiar and unfamiliar, classic and simple variations. There's a lot of puzzle types in here that I havent actually posted on my blog before. The timing of the set was set at 75 minutes, which was longer than the fastest testing. But I have learned from earlier experiences that testing times don't always measure up to the actual test solving. I've added the scores for each puzzle, which equal to 2 points per minute. I think it worked out well, with a mix of easier and harder puzzles. If anyone actually solved them in copetition, I'd love to hear about it.

So here's 14 puzzles in a single post, the most I have done so far. I hope this makes up a bit for the hiatus of a month before. It would of course be easiest to just upload the PDF, but blogspot doesn't seem to offer that option. So instead this post will have all puzzles below.

Puzzle #111: Tapa; Magnetic

This variant was my favourite in constructing during the whole TVC practise series. This was because I was able to do the most with it. I have always loved Magnets puzzles. The first time I encountered them in the Dutch magazine Breinbrekers, I instantly liked how the logic worked. Somehow it just clicked for me. I always have fun constructing them as well. You can have fun with them, especially if you leave out clues like in these puzzles I put on PuzzlePicnic: #1242 and #2160. The combination with Tapa makes for a whole different way of construction. But I liked them best where the Magnets clues lead to the most deductions, instead of the Tapa part.
I think the puzzle worked out well. I wanted to make a 111 themed puzzle and I think it worked out well. It's made in a 11x11 grid. There is one single 111 Tapa clues. It is almost perfectly themed with the magnets clues as well. Each side has 6 1 clues. Just couldn't get the columns set as a three 1 clues for both plus and minus. But I like how it turned out in the end.

Rules for Tapa

Follow regular Tapa rules. Additionally the grid is made up of magnetic and non-magnetic plates. The Tapa wall is made up of non-magnetic plates. Each magnetic plate has a positive (+) and negative (-) side. Sides with the same symbol can't be orthogonally adjacent. The numbers outside the grid indicate how many of the indicated symbol appears in that row or column.

Click to enlarge

Puzzle #110: Star Battle; Clone

This week's puzzle making has been one big stretch of it-just-will-not-work. About every puzzle I tried to make, wouldn't work the way I wanted. When you add to that a bit (or a lot) of stubbornness and I end up restarting a lot of designs and constantly coming to the same conclusion and having to restart.
This puzzle hasn't been any different. I had a certain idea but every time I tried to execute it, I would be forced to break the opening and thus had to restart. So eventually I made it slightly different and an easier version of it. This is the result. I like the opening. I haven't fully checked if there are other ways to open it up, but I like where the intended one is located and how it runs the rest of the puzzle. The puzzle isn't easy, but I wouldn't say overly challenging. Just keep track well in all grids and you should be able to solve it.

Rules:

Place 3 stars in every row, column and boldly marked area. All grids have the same solution. You'll need to use all grids to get to the solution.

Click to enlarge

Puzzle #109: Camping

Yesterday's puzzle was scrapped at the last moment. the puzzle was not unique as I had made a flaw in the opening, so the whole puzzle didn't work anymore. There was really no saving it. I didn't want to just make a quick puzzle and instead moved the posting up a day.

This weekend I won my first LMI monthly puzzle test. I hadn't expected it when I finished it, with how disappointing the last 40 minutes went. In the first 80 minutes I had brushed off all puzzles besides the two "no numbers" genres. I thought it would be best to try to solve both No Number Field puzzles and leave the easy loop for the end. But after really struggling through that easy one, I quickly switched to the loop. The easy one I liked, although I struggled with it a little. I managed about half the second No Numbers Loop in the last 10 minutes. I made a mistake and it took me over 10 tries afterwards to discover what I was doing wrong.
Through Saturday it became clear though that I wasn't the only one who struggled with a few of the puzzles. In the end the top mostly solved the same puzzles, with the big difference being that I did manage to solve the second Synchronised Maze.

Today's puzzle is very old school to me. It was a standard puzzle in Breinbrekers when I first started buying the magazine. It has some similarities to Tents and Trees. The name of the puzzle was "Huisje, Boompje, Beestje" which is a Dutch saying that literally translates to "little House, little Tree, little Animal". The puzzle layout featured a house, a tree and a heart. Because the saying doesn't really translate to English in a way that it's applicable to a puzzle type, I changed the idea a bit. Instead it's represented by a camping ground.
When I first got the magazine this puzzle type always broke me up. I hardly ever managed to solve the puzzles. Then when I first started making puzzles, I tried making one of these. And all of the sudden I was able to solve them. It was the first time I noticed that trying to design a puzzle helps with solving a puzzle type.
There are 2 puzzles. One is a small easy one to help learn a few of the tricks involved. The second one is a normal sized puzzle. It's harder, but completely logically solvable. Hope you guys enjoy them.

Rules for Camping

Easy Puzzle

Hard Puzzle

Click to enlarge

Rules: Camping

Place a number of tents, trees and caravans in the grid. Each tree has a tent and a caravan orthogonally connected to it. No two equal symbols can touch eachother, not even diagonally. The numbers on the outside indicate how many of each symbol are in that row or column.

Puzzle #108: Not Alone

While creating the Black and White Matchmaker as a practise puzzle, I discovered an interesting logic deduction regarding the "Not Alone" puzzle type, which I thought could lead to an interesting puzzle and severely reduce the amount of clues necessary to make it unique. So I tried it and brought it down to only 10 clues. I'm not convinced this is the minimum, but it's far fewer than I thought at first. At first the puzzle reminded me of the Binary puzzles, which are now also published here in a seperate booklet, which I find a boring puzzle type. But this rule is actually far more interesting that those puzzles. This one was pretty fun to create. I wonder how it will be perceived as difficulty. If you realise the one logic deduction I exploited here, it shouldn't be too hard. When you don't realise it, I don't know how people will feel about it.

Rules:

Fill the grid with black or white circles so that each row or column has the same amount of black circles and white circles. One circle of a color can't be sandwiched by circles of the other color horizontally or vertically.
An array of two or more circles of a same color may be sandwiched by circles of the other color  horizontally or vertically.

No Number Practise: Black and White Matchmaker

This weekend is the No Numbers test at Logic Masters India. It is written by Ko Okamato (Xevs). It contains  only puzzles without numbers in the grid, Most types are new to everyone, although I have come across Synchronised Maze before. It might not be my best performance as some of the types are a bit prone to error. The 2 "No numbers" puzzles have to be approached very carefully as it's easy to accidentally leave a number in when you make a small transcription (No Numbers Field) or reading (No Numbers Loop) error. Prasanna created practise puzzles for the other puzzle types, which can be found here, here and here.

I decided to make a Black and White Matchmaker as practise. I've never been any good at these matchmaker type puzzles. I tend to just avoid them unless it's the only one left. In this test it's over a quarter of the points, so probably wise to attempt. Also it contains the most familiar puzzle types. So I figured it would be worth a try to design one so I could find some easy ways to exclude certain types from certain puzzle grids. I've put in a few of ways I found in the grids. The puzzle turned out okay, but with a bit more effort I could have probably made the puzzles overlap in a few more genres.

I've put all puzzles in a single image with a table to match the puzzle types. I also have all puzzle grids as a seperate image. If it would be preferred that I post them all seperately, I can do that as well.

General Rule

There are 6 puzzle grids given with black and white circles and 5 puzzle types. Match each type to one puzzle grid and solve it under that rule. One of the grids won't be used. Certain grids might be solvable under multiple rules, but it's only possible to match them in one way so all 5 rules can be solved in a seperate grid.

Puzzle Types

Masyu:

Draw a single loop that runs horizontally and vertically though every cell with a circle. In cells with black circles, the loop must make a 90-degree turn and go straight in both neighboring cells. In cells with white circles, the loop must go straight and makes a 90-degree turn in at least one of neighboring cells.

Black & White:

Fill the grid with black or white circles so that all of the circles with same color will be connected vertically or horizontally. Circles with same color can't form a 2x2 square.

Sun & Moon:

Draw a single loop that runs horizontally and vertically through every cell in the grid once. The loop can't make turns between cells with circles of the same color, and makes just one 90-degree turn between cells with circles of different colors.

Not alone:
Fill the grid with black or white circles so that each row or column has the same amount of black circles and white circles. One circle of a color can't be sandwiched by circles of the other color horizontally or vertically.
An array of two or more circles of a same color may be sandwiched by circles of the other color  horizontally or vertically.

Signal loop:
Draw a single loop that runs horizontally and vertically through every cell except cells with black circles. The loop goes straight in cells with white circles.

Click to enlarge

Puzzle #107: Blind Spot

Here's another genre taken from Naoki's website. Although I think I've seen it before somewhere else as well. It just seem familiar from a few years ago. So possibly it featured on a WPC at one point.
 The first puzzle I made I liked a lot, except I thought it was a bit too hard as the first one on my blog. So I made another one, which was much easier. But I figured I need something a little bit more challenging to post. So I made a third one, which fell a bit in between both puzzles. And instead of posting just one, I'm going to post all 3. If you solve the example and then the first 2 puzzles in order, you should gradually get all the insights to also solve the third puzzle.

Rules for Blind Spot

Easy Puzzle

 Medium Puzzle

 Hard Puzzle

Rules: Blind Spot

This genre was developed by Naoki Inaba

Place an arrow for all four directions (up, down, left right) once in every row and column. No arrow points at another arrow. Black walls block the view of an arrow.

Puzzle #106: Killer Sudoku With Hidden Cages

This puzzle was inspired by a question raised on a sudoku forum if the Sunday Telegraph's Killer Sudoku With Hidden Cages was also solvable without the constraint that the number was always in the top left cell of the cage. It was never succesfully answered as those killers are probably meant to be solved that way. The Top Left cell constraint is a very powerful one, so it would probably not be unique. From here I figured it might be interesting to try to design a puzzle without that constraint. I'm guessing it's been done before, but I can't directly recall any of them.
I really like how the puzzle turned out. It looks nice and solves really smoothly. The opening probably isn't the most obvious one though. I don't think it's overly hard, but most of my Sudokus turn out a bit on the harder side. I think it's just something that automatically happens when I create Sudoku variants as I like to exploit and explore the opportunities a variant offers. Hope you all enjoy it.


Rules for Sudoku

In this Killer Sudoku the cages are hidden. Each cell with a clue number is part of a seperate cage. Each cage consists of orthogonally connected cells. The number indicates the sum of the digits in those cells. No digit can repeat within a cage. Cages consist of at least 2 cells. No two cages can overlap.

Puzzle #105: Quattro Stagioni (Corral, Nurikabe, Tapa LITS)

I have made a bunch of puzzles for friends for various reasons. Mostly for special occasions. I usually try to theme them in a certain way. This is mostly just based on the way the givens are oriented. For this puzzle though I had the fortune to get three handy numbers to work with, namely 2, 3 and 7. The numbers were handy to build into most genres, so I attempted to use them as best as I could. This puzzle is built up of four quadrants that each belong to a different genre. I thought a while about a good fourth genre to add as Nurikabe, Tapa and LITS have a similar general puzzle idea behind it. I couldn't come up with a good fourth genre that used this type of clue. So I cheated a bit by using corral-like clues, within the same puzzle structure. I think the puzzle worked out well, not overly difficult but still interesting.

Quattro Stagioni

General Rule:
Colour some cells to form a single contiguous shape. The shape doesn't form any 2x2 squares anywhere.

Left Top: "Corral"
The numbers in this section are all part of the shape. The numbers indicate how many cells that are part of this shape can be seen from this shape in horizontal and vertical direction, not including the cell itself. The numbers can't see past white cells. [Note: This section doesn't work like normal Corral. The clue type doesn't include the cell itself. Also there's no loop constraint.]

Right Top: Nurikabe
The numbers in this section each indicate a seperate island of orthogonally connected white cells. The numbers indicate the size of the island they are part of. All remaining cells in this section not part of an island belong to the shape. The islands can cross the border of this section.

Left Bottom: Tapa
The numbers in this section indicate how many consecutive cells are to be coloured around it. If there is more than one number in a cell, then each section of consecutive cells must be seperated by at least one empty cell.

Right Bottom: LITS
In this section colour 4 orthogonally connected cells in every boldbordered region. Two identical shapes in different regions can't touch eachother by a side. Rotations and reflections are considered the same shape.

Click to enlarge

Puzzle #104: Yajilin

I had a pretty good weekend solving sudokus. I finished 13th in the Swiss championship, finishing all puzzles within the set 2 hours. I knew I wouldn't at all be close to the top solvers, so just happy I finished all. I had a lot of trouble with the half squares sudoku and messed up the thermometers on the first try. Although when I recognised my mistake I could just use the second option and the solve was far easier than purely logical.
My Sudoku 8x8 solve leaves me with a bit of mixed feelings. On the one hand I equaled my best performance in an LMI Sudoku test, on the other hand I screwed up in both parts and could have possibly gotten my first top 10 finish. In part A I made a few transposition errors in the Foursome Sudoku, leading to digits in the wrong place and thus having to restart even though the grids I had solved at that point were correct. In part B I wasted my first 20 minutes breaking the Skyscraper, Irregular without regions and Irregular Cube and only finishing the Cube in the end. When I finally got going, I managed to brush off 10 more puzzles in the remaining 44 minutes, but it could have all been far better. But in the end I did as well as I had hoped for both tests.

Now about today's puzzle. On May 10th there was a sudden spike of blog visits, which coincided with the arrival of my latest Akil Oyunlari magazine. This issue featured 4 Yajilin and 4 Tapa puzzles by my hand. Most visits to my blog that day featured my Yajilin pages. So from that I'm guessing people liked them and wanted to try some more. I do think that my Yajilin puzzles on my blog have generally been well received, so I decided to post another one for that reason today. This one is a bit larger than my normal ones, but not as big or challenging as my previous oversized Yajilin. I do think it's again a nice layout of givens, so enjoy.

Rules for Yajilin

Click to enlarge

Puzzle #103: X Sums Sudoku

It's been a while since I've posted. This is mainly just through lack of inspiration on my part. I hadn't written any puzzles for the last month or so.  I recently wrote a bunch again and that went off pretty well, so I'm going to start posting puzzles again.

If you like Sudokus, this weekend can be an enjoyable one for you. With 2 Sudoku tests running, there is plenty to solve. Firstly there's the 8x8 Sudoku Contest on Logic Master India. This competition has 2 seperately solvable parts to it. Both parts have a variety of different 8x8 sudokus in it. One part with regular 2x4 nonets. In the second part the puzzles all have an abnormal layout, either irregular cages, or differently placed 2x4 cages.
There's also the Swiss Sudoku Championship hosted on Logic Masters Deutschland. This is a collection of mostly well known variants. It has a halved squares sudoku in it, which featured in its own round at the WSC in Hungary last year.

This Sudoku will feature in the LMI test. It's an interesting genre, which has some overlap with my own Frameless Sudoku. This idea though needs far fewer clues to get unique though. I am not sure if the puzzle in the championship will also look like this, but I think it's nicer by leaving clues out.

X sums sudoku

Fill in the whole grid with numbers 1-8 so that each number appears exactly once in every row, column and blackbordered area. Numbers outside the grid indicate the sum of first X-numbers in corresponding direction. Number X is always the first number in corresponding direction. F.E. - if the first number in row is 5, the outside number indicates the sum of first 5 numbers in that row.