Product Killer Sudoku


Product Killer Sudoku 9×9 puzzle

If you’re interested in sudoku, come along to the official UK sudoku championship next weekend, the 29th-30th of March, at Selsdon Park Hotel just south of London, outside Croydon. There’s full details on the UK Puzzle Association site. There’s still spaces available.

Mind you, it’s not just sudoku – there’s also the UK puzzle championship taking place the same weekend, and there’s a low price which includes overnight accommodation and most meals for those who take part. Winners of both events get the chance to represent the UK in the World Puzzle Championships and World Sudoku Championships.

One of the puzzles in the sudoku part of the tournament is Product Killer Sudoku, a variant on Killer Sudoku where multiplication, rather than addition, is used.

So: just place 1 to 9 once each into every row, column and bold-lined box. Also place numbers in each dash-lined cage so they multiply to the given total. You also can’t repeat a number within a dashed-line cage.

Valentine Sudoku


Valentine Sudoku
A quick heart-shaped sudoku for Valentine’s Day. Just place 1 to 9 once each in every row, column and bold-lined box.

Brained Up – online daily brain training

Brained UpI’m incredibly excited to announce Brained Up, a cutting-edge brain training site that will help you do just that – upgrade your brain! It’s based around daily online sessions that each provide a wide-ranging mental workout. The site launched just before Christmas, and already has a healthy number of daily users.

Just a few minutes a day is all it takes to upgrade your brain. Visit Brained Up and receive a personalized training plan, optimized to get the best out of your body’s most important organ. Your personal schedule will include a wide range of brain games, ensuring full coverage of key mental skills.
Studies have shown that suitable brain training activity can make you quicker and smarter. This can lead to improved creative, conversational and social skills.
Brained Up features scientifically designed exercises based on extensive research to ensure comprehensive coverage of key cognitive skills, including creativity.

Using Brained Up, just a few minutes a day is all it takes to upgrade your brain. The site constructs a personalized training plan for every user, optimized to get the best out of your body’s most important organ. Every schedule includes a wide range of brain games, ensuring full coverage of key mental skills – as well as keeping it fun throughout.

Studies have shown that suitable brain training activity can make you quicker and smarter, which can lead to improved creative, conversational and social skills. Brained Up therefore features scientifically designed exercises, based on extensive research, to help ensure comprehensive coverage of key cognitive skills, including creativity.

It’s at www.BrainedUp.com.

 

Sudoku Xtra 24

Sudoku Xtra 24

Sudoku Xtra 24 is now finally available! It’s packed with 130 puzzles of a wide range of types, including a huge variety of sudoku variants.

This issue I’ve included a very wide range
of variants, including some new ones such as Two-grid Interconnected Sudoku, Mystery Multiple
Sudoku and Blackout Sudoku. Meanwhile I’ve made an effort to include all of the most popular
variants as requested by readers, such as Consecutive Sudoku, Inequality Sudoku, Odd/Even
Sudoku and of course many more.
If there’s anything you’d like to see in a future issue

This issue I’ve included some new sudoku types such as Two-grid Interconnected Sudoku, Mystery Multiple Sudoku and Blackout Sudoku. I’ve also made an effort to include all of the most popular variants as requested by readers, such as Consecutive Sudoku, Inequality Sudoku, Odd/Even Sudoku – and of course many more.

There’s also a range of non-sudoku puzzles, including Light-up/Akari, Hashi, Slitherlink, Battleships, Skyscrapers, Calcudoku, Futoshiki, No Four in a Row, and more!

It’s available either as a PDF to print yourself (every page is self-contained, so you can print only the pages you want), or as a professionally-printed book direct from Amazon – there are links for all of these on the Sudoku Xtra site.

Sum Skyscraper


Sum-Skyscraper 5×5 puzzle
I made this puzzle just before Christmas, and it’s been waiting on my desktop to be posted here ever since! Well, now it finally has been. :)

This is a Sum Skyscraper. Place the digits 1 to 5 once each into every row and column in the grid. Numbers outside the grid provide the total (i.e. sum) of ‘visible’ grid digits along that row or column, if you imagine each digit as a building of that many storeys. Taller buildings always obscure shorter ones. So, for example, a clue for 21354 from the top of such a column would be 10, since the 2, 3 and 5 are visible (the 1 and 4 are obscured by the 2 and 5 respectively), and 2+3+5 = 10.

Christmas Star Sudoku


Sudoku Christmas Star puzzle
A Sudoku, in a star shape.

Just that. (Place 1-9 once each into every row, column and bold-lined 3×3 box).

Bridge Mazes


Weaved Bridge Maze 2

Weaved Bridge Maze 1

I’ve recently been making some material for a book of kids’ mazes, and so I thought it would be fun to post a harder version of some of those puzzles here.

First-up, here’s a weave maze, so-called because the paths weave over and under each other. In this puzzle I’ve drawn narrow bridges where one path crosses over another.

If the first one is too easy for you, try the second! It needs to be printed full-page in order to have enough space to solve it.

Just enter at the top of the maze and follow paths until you exit at the bottom of the maze.

Wraparound Numberlink

Flow Free book coverI’m currently working on a forthcoming book (The Mammoth Book of Brain Workouts, published next year in the UK by Constable & Robinson, and in the US by Running Press), and have been experimenting with something I wrote about briefly a few years ago but hadn’t really tried since – variants on Numberlink.

Numberlink puzzles have proved popular recently in various guises, including Flow Free and other apps on mobile devices such as the iPhone. There are quite a few such apps available, but none of them force a unique solution on the user (and generally the puzzles do indeed have many different solutions), which when you’re playing against a computer that grades you isn’t necessarily a problem since you can at least be marked correct/wrong automatically.

For a logic puzzle solver, such vague puzzles are perhaps a bit disappointing because you will reach a point during solving where you can’t eliminate any options because they may all be valid, despite being contradictory.

I’ve made a printed book of 200 of these Flow Free puzzles – you can get it from Amazon.com (currently $5.36) or Amazon.co.uk (£3.95) – and they’re actually quite fun to solve despite the multiple solutions (not all the puzzles have multiple solutions, but some do). Unlike traditional Numberlink the puzzles include an explicit rule that every cell in the grid must be used, which eliminates a lot of potential solutions and means the puzzles usually require some thought.


Toroidal numberlink 6×6 puzzle


Toroidal numberlink 5×5 puzzle

But such multi-solution puzzles are not the kind of puzzle I usually post, so I’m going to stick to logic puzzles with unique solutions on this blog.

It turns out that if you allow lines on a Numberlink puzzle to wrap around one edge and come back on the other – so if a line goes off one end of a row or column it comes back on at the other end of the same row or column – that the puzzles get very difficult very quickly. In fact, even at 5×5 many such puzzles are very challenging. Once you get to 6×6, I have real trouble with them.

Here’s a 5×5 and a 6×6 puzzle for you to try. Let me know how you get on! There’s no explicit rule that every cell must be used – but as a hint I can tell you that they are anyway. There’s a unique solution to each puzzle.

101 Giant Sudoku series

I’ve recently launched a new series of ‘101 Giant Sudoku’ books, to cater for those who like their Sudoku to be considerably larger than normal!

You can see the entire series at PuzzleBooks.org (scroll to the bottom) or visit Amazon and search for “101 giant sudoku”.

There are currently 12 books in the series: 14×14, 15×15, 16×16, 18×18, 20×20, 21×21, 22×22, 24×24, 25×25, 28×28, 30×30 and 36×36.

The larger puzzles work just as you’d expected, so in Sudoku 36×36, for example, you must place 0-9 and A-Z into every one of the 36 rows, 36 columns and 36 6×6 boxes!

These puzzles are designed so they don’t need any advanced logic – just scan the rows and columns and boxes to see what’s missing and what can fit where.

All of the puzzles are designed with attractive 8-way symmetry patterns.

Sum Skyscraper puzzles

Following-up yesterday’s Skyscraper puzzles, I thought I’d post a couple of Sum Skyscraper variant puzzles.


Sum Skyscraper 6×6 puzzle


Sum Skyscraper 5×5 puzzle

Sum Skyscraper puzzles are very similar to Skyscraper puzzles, so no number can repeat in any row or column and external ’skyscraper’ clues reveal information about the numbers in the main grid. In 5×5 puzzles place 1-5, and in 6×6 puzzles place 1-6.

Each number in the completed grid represents a building of that many storeys, and place the buildings in such a way that each given number outside the grid represents the sum of the number of buildings that can be seen from that point, looking only at that number’s row or column. A building with a higher value always obscures a building with a lower value, while a building with a lower value never obscures a building with a higher value. So the clue ‘6′ in a 5×5 puzzle would indicate that the buildings ‘1′ and ‘5′ can be seen (’5′ is always visible in 5×5 puzzles), so the solution to a row might be 15234.