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February 3, 2012

Revenge of Killer Sudoku: Killer is the right word!

Filed under: Reviews — djape @ 9:00 am

Since my books are now available on Amazon.co.uk and other international Amazon websites, I will post a few reviews of my books from those websites.
Of course, the books are all the same on all websites, so these reviews are valid no matter where you’re buying the books. icon smile Revenge of Killer Sudoku: Killer is the right word!

First up…

Revenge of Killer Sudoku

This is my first book in the Revenge series and some argue that it is the best one. It introduced Zero Killer Sudoku puzzles for the first time.
There are 8 reviews of this book on Amazon.co.uk. 7 reviews are 5/5 stars, 1 is 4/5 stars.

Here are all 8 reviews by people who bought and solved puzzles in this book.

Most challenging killers I’ve found

5/5 stars
I love Killer Sudokus and have always strived to find difficult puzzles to tackle.

The 1st Killer Sudoku book by Djape offered just that and was excellent and left me desiring more. So I purchased the appropiately named Revenge of the Killer Sudoku and spent far more time than I could afford struggling through it.

The zero (blank cages) at the end kept me quiet for hours, and 1 of the earlier puzzles beat me completely (number 139 if anyone is interested).

My wife was sick and tired of seeing me slouched on the chair every spare moment I could find, head in book, grunting at her attempts to prompt me out of it. She wasn’t very happy about me purchasing revenge 2 when I finally reached the end of the book and won’t be pleased to find I’ve just oredered volumes 3 and 4.

If you like a challenging puzzle then these are the best and most difficult I’ve found and offer way too many hours of ‘fun’.

Excellent

5/5 stars
I struggle to find killer sudokus that are difficult enough – most books have a very large portion that are far too easy with only a few challenging puzzles at the end. This, howevever, has harder puzzles right from the start. At first it took me a while to get used to the way the book is printed (I had been used to The Times ultimate books) but this didn’t take long. If you’re a beginner try something else first, but if not then choose this – I have yet to find anything more challenging!

Killer!

5/5 stars
A great book. DJApe’s puzzles seem fresher, more interesting and definitely more challenging than the Times ones (comparing the hardest ones). I particularly like the Zero killers where many of the squares are left blank. Seems to open up some further and beautiful lines of deductive reasoning – as well as being an interesting hybrid of normal and killer sudoku.

To sum up DJApe is continually pushing the boundaries of these puzzles rather than going through the motions and if you are looking to be challenged is the place to come! Good luck to him/her?! (I still enjoy the Times’ ones but have never got stuck on them and they seem more of a work-out than a challenge I might not succeed at within a reasonable time-frame.)

Sudoku Revenge.

4/5 stars
Not over keen on the presentation of the puzzles.
All the totals are NOT top left – which may seem petty, but it caused me to put the book away rather than swop between formats.
I can’t put my finger on why I do not like the dotted lines and none square boxes.
Still lots of puzzles for the price, though I have not got to the harder ones yet.

if you liked this, seek out “revenge 2″

5/5 stars
RE Vol 2, I do not understand why it is not available on amazon uk, but you can either get it on amazon.com, or as a download – it is a great progression from this first book, for everybody who is getting bored with a big chunk of “baby” puzzles at the start of a book – I got the download version, and the best thing is, you can reprint fresh pages at a later date and redo it all… sad? I should say so!
Djape’s puzzles are a cut above the rest, with NO guesswork required to find the solutions. Highly recommended, both book 1 and 2 (and now, I believe, 3!)

A step up from The Times

5/5 stars
After cutting my ‘Killer Sudoku’ teeth on the 4 Times KS books I found this to be a step up. The books quickley become challenging and often give you very little to start the puzzle.
My only moan is that I’m a bit of a scribler and there’s very little space around the puzzles to do any calculations etc, but that’s a minor point.
An excellent book.
Do I no buy the next Times book when its released or will I find it too tame?

Another killer killer

5/5 stars
Excellent book. 150 puzzles; 100 of which are of the best, difficult, quality. This chap knows his killer sudoku.

Killer is the right word…

5/5 stars
If you’ve done the puzzles from DJAPE’S other book then this is what comes next. The puzzles start with “cool” level and move onto to “IQ”. At the end of the book are some puzzles with blanks in the grid for you also to work out. The IQ puzzles are seriously difficult and can leave you wondering if it was really meant to be this hard. If you are an addict and don’t want to waste money on a book with too many easy puzzles then you will not be disappointed. If you are new to Killer then work through the Times books first then progress to this. Lets hope there’s another book soon… in the meantime killersudokuonline on line will have to do.

































The original reviewers can ask me to remove their reviews if they don’t like them shared here.

January 31, 2012

Hitori puzzle: big and difficult

Filed under: General — djape @ 5:22 am

It’s been a while since I last posted this kind of puzzle. You can read about these “reverse sudoku” puzzles here:
- The rules of Hitori
- How to solve Hitori

This one I’m posting now is going to be a difficult one. I hope. Some have claimed that my Hitori puzzles are not difficult. What do you think?

Hitori 15×15 for January 31, 2012.

hitori puzzle difficult 20120131 15x154 IQ u19 0 0 0 0 0 0 1 2 3  c225 0 690 300x300 Hitori puzzle: big and difficult

Hitori solution

January 27, 2012

Asking for a favor from university students

Filed under: General — djape @ 9:41 am

I have a favor to ask all of you folks, particularly University students among you. I get lots of visitors from .edu domains, and I suppose most of you are students (or perhaps there are some professors too?).

Anyway… .edu domains are important. Search engines value links from .edu domains more than others. Lately I’ve been trying to optimize my website for search engines.

Would those of you who have student pages (or professor pages) on their University websites post links to my Daily Killer Sudoku or Samurai Sudoku pages? That would mean a world to me!

Something like this would suffice (copy&paste onto your student webpage)

Samurai Sudoku


Killer Sudoku


Of course anyone else with a website is more than welcome to put these links to my website. icon smile Asking for a favor from university students

Thanks so much in advance folks! You can post a link back as a comment here if you like icon smile Asking for a favor from university students

January 20, 2012

My puzzle books are available on Amazon UK

Filed under: Bookstores — djape @ 3:07 pm

I noticed in the last month or so that my sudoku and other puzzle books are now available more regularly on Amazon.co.uk and other international websites.

Many of you who come from the UK have asked about the books not always being available there, so now it seems like it’s been sorted out. Hopefully. It’s really not under my control, so just as you I hope that you can reach them without them being “out of stock” or whatever.

Also, I’ve updated the links on this website accordingly, so now if you click on book covers it should take you to your country-specific Amazon website. Below are the links to my books on all Amazon websites.

There are some nice reviews of my books on these websites. Thanks for that folks! icon smile My puzzle books are available on Amazon UK I hope you write more of them!

navAmazonLogoFooter. V28243301 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V28243210 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V28243269 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V28243280 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V28243234 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V185350640 My puzzle books are available on Amazon UKnavAmazonLogoFooter. V183003497 My puzzle books are available on Amazon UKnavAmazonLogoFooter My puzzle books are available on Amazon UK

January 14, 2012

Why do I make puzzles? A brief history of Djape.net

Filed under: General — djape @ 4:20 am

A short answer to that question would be: because I enjoy doing it! … but here is a long version, too.

Back in the summer of 2005 I realized that it’s about time I had my own website. At that point I had been computer programming for years and it kinda made sense that I should have a piece of the www for myself. So I bought the domain djape.net. Why that one? Well, because .com was already taken (and still is and it’s still “under construction”!!!). Djape is popular among people with my first name. icon smile Why do I make puzzles? A brief history of Djape.net Oh, and why Djape? Well, because that’s my nickname. Actually, my nickname is Pedja (just like recently retired All Star Pedja Stojakovic of the Dallas Mavericks), but Djape is a common variation (it’s an anagram, the two syllables are reversed). I also thought DJ APE, no matter how stupid it sounds, would be something easy to remember for English speaking folks.
Here you can hear me pronounce my nickname.

Yes, that was my voice, recorded a few minutes ago.

Anyway… now that I had a domain, what should I put on it? Earlier in 2005 I learned about Sudoku and actually I had already started creating my own software for solving and generating Sudoku puzzles. I thought, this could be interesting to other people, so I decided to put it on my website. Now, I’m a software developer, not a web-designer, so I installed a WordPress blog and started “blogging” about Sudoku.

At that time a number of Sudoku websites already existed and I realized that I had to offer something different. I added Diagonal Sudoku and Sudoku of different sizes (4×4 or 16×16 etc) first. However, in early September 2005, while surfing around, I stumbled upon The Times of London website and learned about Killer Sudoku. It immediately impressed me as a cool new variant of Sudoku and I immediately started working on my algorithms, first for solving Killer Sudoku and later for creating them.

It took about 10 days to implement a Killer Sudoku generator. On September 26, 2005, I started posting Daily Killer Sudoku puzzles. On September 27, the Killer puzzle I posted caused some controversy. Why? Well… at that time my Killer Sudoku generator algorithm was still far from perfect. It used trial and error to create&solve puzzles. It even had two singleton cages, something that I would NEVER publish now! Frankly, I wasn’t paying much attention to which puzzles I was posting on a daily basis, I spent most time working on the algorithm. And that one puzzle changed the course of this website. People showed interest, The Times’ puzzles were too easy, everybody wanted something more difficult. The September 27 puzzle was valid in the sense that it had a solution and it had only one solution, just like all other puzzles I ever posted.

If you click on the above link to Sep 27 puzzle, you can still access it, but don’t try to solve it. It’s almost impossible. It was the first INSANE Killer Soduko puzzle. Some visitors had made a lot of progress on it, and a guy called udosuk provided a solution to the September 27 Killer Sudoku puzzle with only minor trial and error. By the way, if udosuk is still visiting this website or if anyone has his contact, I’d like to get back in touch.

In the meanwhile, I perfected the Killer Sudoku generator and starting posting daily puzzles only of top quality. There was no more trial and error (although many visitors kept asking for INSANE Killers), every puzzle was human solvable, mostly by using variations of the Rule of 45 technique. Later I started adding a personal touch to the puzzles, by interactively designing them and only letting the computer do the hard work.

Anyhow… the Sep 27 puzzle and the people’s reaction to it, gave me incentive to keep making puzzles. The number of visitors to the website increased, I was interacting with people from all over the world from the comfort of my home (there was no Facebook back then! icon smile Why do I make puzzles? A brief history of Djape.net ) and it only made sense to continue doing it. Later that year I added overlapping Sudokus to my software (much easier implemented than Killer Sudoku) and among them, of course, Samurai Sudoku.

Eventually, publishers started contacting me. First was Via Optima from Portugal, who published my first book of Killer Sudoku puzzles. Then some lady from the UK sent an e-mail and later called me on my phone, also showing interest in publishing Killer Sudoku, but then disappeared. Finally, through a guy from another Sudoku website, I got in touch with the editors of The Washington Express who wanted Samurai Sudokus in their paper. They started printing Samurais in December 2005. Shortly afterwards, The Washington Post followed suit and in January 2006 published my first Samurai Sudoko puzzle.

Later a publisher from Finland asked me if I could made Hanjie puzzles for them. And I did. These are, of course, hand-made puzzles, only checked for validity by my software.

Other publishers followed. I started self-publishing books on Amazon. This was an important step and I am really happy to read your reviews of my books. Please, if you buy my books, please review them on Amazon, it means so much to me.

There’s more history, but even this is more than just a “brief” version, so I’ll leave the rest for some other time.

I make puzzles and puzzle books because it’s my passion. I do it all by myself, even the book covers! That’s why they look so childish (except for a few which were done by a friend who is a designer). Most of all I enjoy programming new types of puzzles into my software and communicating about new puzzles and my books with people who buy them and solve them. This is why I engage so much in social networks. Your reaction is important to me and it does influence my decision. Add me on Facebook, Twitter or Google+. And share with your friends! icon smile Why do I make puzzles? A brief history of Djape.net

When I publish the puzzles, I either interactively create them using my software, or generate them automatically and then hand pick them, verify the solving paths and check the difficulty. Most puzzles by other authors are too easy. I know, that because I create difficult puzzles the target audience is smaller; but I believe that the joy of having solved a difficult puzzle is much much bigger than solving a trivial one. Hence, my joy as the author also grows! I prefer to create puzzles that will get a review like this one.

This must be the longest post ever on this website. It was intended as a “brief history” but it turned out much longer than I anticipated. Oh well… icon smile Why do I make puzzles? A brief history of Djape.net I felt like writing it. Hope it wasn’t too boring!

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