Yeah, that title sounds scary, don’t you think? But before that… Happy Thanksgiving, folks, if you happen to give thanks today!

So… a first book in the new series of books with killer sudoku puzzles is now published. It is something in between the “Revenge of Killer Sudoku” and “The Deadliest Killer Sudoku” series, at least as far as the difficulty of the puzzles within goes.

There are **NO EASY, NO COOL **puzzles in this book! Difficulty levels are THINKER-BRAIN-IQ-INSANE. The breakout of puzzles is as follows:

- 100 classic Killer Sudoku 9×9. Half of them are THINKER, 30% are BRAIN, 20% are IQ.
- Another 10 classic 9×9 Killer Sudokus, all of them INSANE!
- 10 ZERO Killer Sudoku
- 10 Killer Sudoku with all four arithmetic operators +,-,*,/
- and my new personal favorite… 20 Killer Sudokus 10×10, using all 10 digits from 0 to 9!

The book is waiting for you to order. And use that coupon! The price will go up a bit in the next couple of days!

]]>First up: A new Samurai Sudoku book is out! It’s actually a SUPER Samurai book. This is a new series which will contain more puzzles than the previous Super Samurai Sudoku series of books. Why? Because the last 10 puzzles will be a variety of super samurai, including some LOCO Super Samurai Sudoku puzzles!

Anyhow… this book is available to order and ship immediately. Be quick, because in a couple of days the price might go up a little!

]]>**Important: ** The price on these books is discounted by about $2 or so. When they get published, which is in about a week’s time, the price will go back to normal.

In order of their publishing dates, the books in question are:

- Super Quad Sudoku Samurai will be published on November 21. It’s a new series of books with Super Samurai Sudoku puzzles and it contains 10 puzzles more than the previous series!
- Coming up a day later, on November 22, is a book with 150 Killer Sudoku puzzles of medium and hard difficulties: THINKER-BRAIN-IQ-INSANE. It is a new series called “The Return of the Killer Sudoku“. There are a few killer sudoku variants in there. It is not meant to replace neither “the deadliest” series, nor “the revenge” series. It is something in between those two (but somewhat closer to the deadliest killer sudoku series).
- Then, on November 23, a completely new book with 100 brand new Nonograms-Griddlers-Picross-Hanjie puzzles is released.
**All puzzles are new, previously unpublished**(unlike in the 600 nonograms book). - And last, but certainly not the least is the book simply called “Puzzles by Dr Djape“. This book will be released on November 24, 2017 which marks the first anniversary from the date when I defended my PhD thesis. This book contains 100 sudoku variants and 17 other puzzle types, for a total of 300 puzzles altogether. It’s a very special book with very special puzzles. I hope it turns into a series!

Here is another example of the bordering technique applied in a different way.

Consider this partial nonogram in which only the top few rows are shown. Focus on the first three rows and the “7” clues in them. Where can or cannot this “7” clue in the first row begin? Notice the circled “1” which belongs to column 5.

Can the “7” of the first row begin in column 1? It can’t. Why? Because if it did, the “2” in column 2 would also kick off the “7” in row 2, but the “1” in column 5 would stop it before all 7 squares in row 2 are filled, because after the “1” in column 5 there must be a blank square. Get it? Think about it for a while and consider what happens with the perpendicular lines when the “7” of the first row begins right at the start of the row.

Continuing this logic, we can conclude the same for the first four squares of row 1 and get to the following position (the red “X”s mean “certain whites”).

Now, let’s extend this logic to row 3. Look at all the circled “2”s, which are the first clues (this is extremely important) in their corresponding columns. Looking from the start of row 1, the first two circled “2”s prevent the “7” of row 1 starting anywhere before the “2”s, because the “3” nested between the two “2”s would extend to row 3, but it would be a lonely black square in row 3 because there would be a white to the left and to the right of it, because of the “2”s. Think about it for a while.

Finally, now start applying this logic looking from the end of row 1 backwards (right-to-left). The “2”s are circled and should help you conclude that none of the last 7 squares in row 1 can be black and therefore, must be white.

Does this make sense to you? Please do comment and/or ask questions if you have any doubts.

]]>Two announcements:

I sent out a newsletter yesterday in which I informed you that from now on, my books will be available for **pre-order**. More about that in a second, but first, let me tell you that another collection of 1000 Kakuro or Cross Sums or Number Cross or Crosswords with numbers puzzles has been published. This is volume 2 in the series and it actually contains more than volume 1. The number of puzzles hasn’t changed, it’s still 1000 Kakuros, but half of them have grown in size, so there is actually more to solve than in previous volume!

**IMPORTANT**: The book is right now **discounted** and it’s just **$19.99 for 1000 Kakuro puzzles**! For a very limited time you are getting a **$5 discount**, so now is the time to get it! First in best served, while the promotion lasts!!!

This book is already released and you can order it and it will be shipped immediately. However, future books will be available for pre-order and one of them actually already is available for pre-order!

It’s a new series with Super Samurai sudoku puzzles and once again, in this new series you get more puzzles for your $! Click on the image to find out more… This book will be fully released on November 21. Until then you can add it to your wish list or actually pre-order it and it will be shipped on November 21.

]]>The difference is that this series **WILL BE CHEAPER** and it will contain fewer puzzles. 65 Killer samurai puzzles for $9.99 is a great deal!

The book is already available on Amazon and other online stores and you can access it by clicking on the image below.

]]>**IMPORTANT**: The book is right now **discounted** and it’s just **$21.99 for 1000 puzzles**! For a very limited time you are getting a **$3 discount**, so now is the time to get it! First in best served, while the promotion lasts!!!

First up, something that I hinted in my previous post: The Massive Book of Picross Hanjie Griddlers Nonograms with more than 600 picture puzzles has been published!

This is the book with the largest number of griddlers out there. Be warned: all puzzles in this book have previously been published in the first 6 volumes of my hanjie-picross series of books.

The price may seem high, but this is really **a great value for your money**! For under $40 you get 6 volumes worth of puzzles, which would cost you over $80! So you are getting the same number of puzzles for less than **half the money**!

The puzzles have been overhauled and slightly modified in appearance. The fonts are bigger and the lines are thinner so that the available space on a page would be used better.

If you like picture puzzles, this book is an absolute must!

And here is something I can already reveal: in a couple of weeks a new volume with ALL NEW HANJIE puzzles will be released. Stay tuned for updates (best is to sign up for the newsletter).

]]>So, that’s about to change and I’m immediately starting with an advanced solving technique, which I call “**bordering**“.

Consider this example (it’s a part of a griddlers puzzle that I’m working on right now).

Focus on the two bottom rows and on the corresponding clues. I claim that the cell marked with a red question mark cannot be black, it must remain white. Why? If it were black, the “5” clue, whichever of the two fives it might be, would stretch from this black either to the left or to the right, or a little bit to the left and a bit to the right. Now, see the clues on the top of the image. The clues highlighted in red are all greater than 1 and they are all last clues for the column they apply to. This means that the last patch of blacks in the corresponding columns consist of at least two black cells. In other words, if these patches of blacsk started in the bottom row, they would extend at least to the penultimate row of the puzzle. Get it? Now, if “?” were black, there would be a patch of 5 black cells which would all extend upwards for 2 or more cells, because of the clues on the top. This means that in the penultimate row there would be a patch of 5 cells, too, which must not happen, because the largest clue in the penultimate row is 2! Therefore, the “?” must be white! Get it?

But that’s not all! See if you can figure out how many other cells in the bottom row also can’t be black. I will reveal the answer at the bottom of this post.

Before that, let me tell you that I’ve published a new book with nonograms puzzles. There are 600 of them in this book! It’s the largest picross book out there. But more about that in a couple of days.

Ok, now, are you ready to see the answer? None of the cells marked with a red X cannot be black, they must be white!

The rule for the “bordering” hanjie solving technique can be generalized as follows (are you ready?):

If the smallest clue (we’ll call it X) in the bottom row is greater than the largest clue (we’ll call it Y) in the row above it, and if there is a string of at least 2*Y+1 adjacent columns in which the last clue is greater than 1, than the cell in the bottom row which belongs to the column in the middle of the string of Y columns cannot be black, it must be white!

Why this term 2*Y+1? Because the “X” clue could come either from the left or from the right, so you need at least twice as many clues plus 1 to get more than Y black adjacent cells in the penultimate row.

In my example, X=5, Y=2, and just by chance 2*Y+1=5 (but it doesn’t have to be the same as X). What’s important is that X>Y and that there are at least 2*Y+1 adjacent columns with bottom clues bigger than 1. In my example, there are actually 15 such adjacent columns, but be careful, you cannot put a certain “white” in all of them, only in the middle 15-2*Y. Also, this partial puzzle shows that you can apply the same rule twice to the bottom row. There is another string, this time with precisely 5 adjacent columns and now you can mark only one cell as a certain white (5-2*Y). That’s the last red X in the image above.

Due to symmetry, the same principle applies to top rows and of course to first and last columns.

Study this example and think about it. It should all make sense. Let me know what you think!

]]>Before you try solving this puzzle, please become familiar with the Clueless Sudoku puzzles and with the Loco Sudoku puzzles, too.

Just to help you out with the instructions for this particular puzzle. There are 9 puzzles which all seem to be separate from the rest, each on its own. However, there is a trick! There is also a 10th puzzle which comprises of the 9 central nonets (3×3 boxes) from each of the 9 puzzles. The 10th puzzle is a plain old classic 9×9 Sudoku (aka “vanilla sudoku”). The name “clueless” comes from the fact that the 10th puzzle starts completely clueless (i.e. empty), because all 9 central nonets start without any clues! Get it?

Now… since this is a LOCO sudoku variant, I must tell you what the 9 constituent puzzles are:

- TOP LEFT: jigsaw sudoku
- TOP CENTER : NON-CONSECUTIVE sudoku (it looks like vanilla but it is not!!!)
- TOP RIGHT: jigsaw combination sudoku
- MIDDLE LEFT: hyper sudoku
- CENTER PUZZLE: diagonal sudoku
- MIDDLE RIGHT: inequality sudoku (greater-less than)
- BOTTOM LEFT: consecutive sudoku
- BOTTOM CENTER : partial odd-even sudoku (shaded=odd, square=even, blank=unknown!)
- and BOTTOM RIGHT: KILLER sudoku!

Again, I remind you that the 10th puzzle is a plain vanilla sudoku!

Are you ready for this!?

PDF Version of this puzzle: Clueless LOCO Sudoku puzzle in PDF.

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