Mailbox + Vote for NH5

All the puzzles from Nikoli Hurdles 4 are now available at the PAST COMPETITIONS tab above. Before we move on, a proper send-off is suitable. I’ll share some thoughts and a few feedbacks from the solvers.

Also here’s a chance to see your favourite puzzle in NH5.
You can vote for up to 4 types (among puzzles beginning with S) and voting closes on 8th December.

Mail box:
Michael T: I’m a newcomer to logic puzzles so this introduced me to some nice new types like LITS and Masyu. I thought Masyu was the hardest by far, although probably someone more experienced would have a much easier time.

Masyu and LITS are as common as logic puzzles go, and I seem to have taken it for granted. I hope future events don’t scare away potential puzzle solvers. And to be fair, the Masyu was no-walkover, it was quite difficult.

The most talked about puzzle was Puzzle 8 (Tile Paint).
Here’s some selected comments.

Edison: I could see that it was a picture of junk food. I tried HAPPYMEAL before MCDONALD’S though
Prasanna:  The last answer could be HAPPYMEAL just as well as MCDONALDS😉

Ahh.. I did not think of HAPPY MEAL (coincidentally also 9 letters long) at all. Even if I did, I’d still go with the more foreigner-friendly MCDONALDS as the answer.

Kishore: I had to seek help of someone else to complete it. I have never been to Mcdonalds nor seen their logo. Better to avoid puzzles of [this] sort.

Apologies about my ignorance of McDonalds being unfamiliar to certain people, maybe because I’m just a fast food nut.

Nikola:  I almost gave up when my 5 years little girl recognized the final picture!

I like this story a lot. That last time you took her to McDonalds paid off!

I’m a sucker for colourful variety puzzles so the personal favourite puzzle award goes to Hamburgers. This type is a knock-off of Yosenabe. Instead of adding numbers, you had to make hamburgers. The idea came from Nikoli Puzzle Communication (issue 141) where the puzzle took the theme of making a hot-pot. I went with the more well-known burgers – also tying it with the McDonalds theme at the end.

Nikoli Communication 141

Nikoli Communication 141

Antonis: The Hamburgers thing was quite unexpected – the design may have legs.

The original version I wrote was a killer, easily a puzzle 8. But when I tested it, I thought I would make it easier by tweaking some of the regions. It turned out that the change allowed a crucial initial step to be bypassed – which made the puzzle tremendously easier.

You could start by guessing which dish belonged to the Filet-O-Fish and the puzzle pretty much solves itself. I was very annoyed at this point, but I had already spent 3-4 hours writing it and my roommate wasn’t happy with me staying up and using the light so I retired to bed🙂

Thomas: Maze, Nansuke, Hamburgers and especially Block Party were excellent in both solving and bringing something a bit different from the usual types.
Ivan: Hamburgers (not sure the actual type) was too easy.
Giovanni: The Yosenabe gave me a bit of a problem too, but I found the logic and it solved nicely from there.

James: Also wondered if the “Menu” was a hyperlink clue, but couldn’t find anything smart to do with it.

And we have an easter-egg hunter!
There were 2 secret puzzles hidden in previous events. One, where a lot of people found, was in Manila. And one, where no one found, was in … oh… better keep it to myself for now since I might re-use it later.😉

Bonus fact. Originally, I had 5 SOTR veterans as the names of the burgers, but dropped all of them for simple names instead. Somehow, [Nick] Brady’s BLT survived the cut.

That’s it for now, until next time!

Results of Nikoli Hurdles 4

36 people have made their trip over 8 hurdles during the past month. Among the finishers; we have 11 former prize winners and 6 newcomers. Welcome, welcome!

Let’s play Minority Decides!
Take note of your number and see how far you went. Numbers are assigned by order of submission:

  1. Edison He,
  2. Zach Polansky
  3. Grant Fikes
  4. Nick Brady
  5. Stefan Tomlins
  6. Ivan Koswara
  7. Ken Levine
  8. Antonis Lalatsas
  9. Robert Vollmert
  10. Michael Lasserre
  11. Walker Anderson
  12. Prasanna Seshadri
  13. Min-Young Joo
  14. Matej Uher
  15. Nikola Zivanovic
  16. Arturo Vial Arqueros
  17. James McGowan
  18. Kishore Kumar Sridharan
  19. Alan O’Donnell
  20. Tom Collyer
  21. Thomas Powell
  22. Jakub Hrazdira
  23. Swaroop Guggilam
  24. Gavriel Hirsch
  25. Liane Robinson
  26. Michael Mosshammer
  27. Franck Wallez
  28. Neil Brown
  29. Victor Larsen
  30. Michael Tang
  31. Grayson Holmes
  32. Fernando Almazan Gil
  33. Giovanni Pagano
  34. Andrew Brecher
  35. Sumet Juariyamark
  36. Moyd Farhan Bin Hassin

Here we go!

Question 1: Do you like hamburgers?
A: Love’ em!
B: I’m more of a salad person

16 people chose A
20 people chose B
Correct answer is A!
16 hamburger-eaters are moving on!

Question 2: You are in a shopping mall, where do you go to whet your appetite?
A: McDonalds

8 people chose A
8 people chose B
No correct answer, we’ll move onto the next question.

Question 3: What sauce would you like that with?
A: Tomato sauce, please
B: Mustard, please
nh4resc5 people chose A
11 people chose B
Correct answer is A!
We’re down to just 5 people!

Question 4: And your choice of sides?
A: Crispy fries
B: Chicken nuggets
nh4resd1 person chose A
4 people chose B
Correct answer is A!

Congratulations to Ivan Koswara from Indonesia!
He wins the Nikoli Puzzle the Giants 2016 issue!

Warm applause to Michael, Min-Young, Andrew and Sumet for coming so close. Interestingly, the correct answers were all A’s. Ivan’s submission of AAAAAAAB won him the event outright. We had two submissions from Tom and Farhan who went with BBBBBBBB, right concept but wrong letter!

Ivan has been a long time veteran of this blog, submitting entries since Nikoli Hurdles 2 without missing a single event. I’m happy he is finally rewarded. As for everyone else, thank you all for participating and I hope to see you again next time. If you want a reminder to your inbox – hit the Subscribe button on the right and guarantee you’ll never miss an event.

Until next time…

Happy Halloween!

Finish Line list added


We are approaching halfway of Nikoli Hurdles 4.

On the right hand side of this page (if you’re viewing this on a computer), you should see the list of people who are already at the finish line.

You have over two weeks to join them!
Special kudos to Edison, Zach and Grant (you’re the bad foxger!) who are our top 3 for this event. But in the end, everyone is on equal ground for winning the prize. If you think your name is missing, please resubmit your entry.

Good luck!

Flashback #20 – Product Sudoku

This puzzle was used in a final sprint round so the medium-level was appropriate. I’ll let you in on a secret; when sudoku authors run out of theme ideas, they take a blank grid, plonk in 1-9 along the main diagonal, take a step back, seek more inspiration and hope something good comes out of it.

That was pretty much how this puzzle came about.

Product Sudoku: Classic sudoku rules apply. Given numbers between two cells  indicate the product of the two numbers in those cells.


Flashback #19 – Retrograde Battleships

My first retrograde puzzle!
So far I’ve seen retrograde tetrominoes, pentominoes, scrabble, and battleships. Retrograde puzzles are harder for writers than it is for solvers. Firstly, the author has to prove that the solution his unique (very hard to do) and, should the puzzle be too difficult for logical reasoning, solvers can always hack the puzzle by guessing (not hard to do).

Retrograde Battleships appeared in the 2000 WPC and 2001 USPC. The one that I first saw was by Cihan Altay (where is he nowadays?), and Akil Oyunlari had a puzzle book with lots of them in a Battleship variants section. I recall tediously testing all possible combinations to ensure that the puzzle had only one solution.
Thankfully, it did.
Here it is.

Retrograde Battleships: Locate the given fleet in the grid, with regard to the shapes of the cells. The ships cannot touch each other, not even diagonally. The ships may be rotated.

retrobateg retrobatpuz

Flashback #18 – Five Pair Sudoku

Let’s move on to a sudoku.
The first Five-pair Sudoku I saw was written by Vladimir Portugalov. Several followed in his Forsmarts website and his 24HPC sets. I like solving medium-ish puzzles so I keep that difficulty in mind when I’m constructing. Unless I’m out to get you (like a heavy-pointer in a puzzle set or a giant puzzle for last year’s WPC) I’m generally nice to solvers.🙂

Five-Pair Sudoku: Classic sudoku rules apply. Additionally, each 10-cell grey area should contain two identical sets of 5 digits. The two grey areas may contain different sets.


Flashback #17 – Tetromino Minesweepers

Back in 2012, the UKPA held its first offline event in Manchester. I believe it was the only year that the organizers posted the puzzles online simultaneously for solvers around the world to compare their scores. The reception online was dismal so that idea was abandoned later on. I contributed some puzzles and sudokus for this event and I’ll be sharing my favourites over the next few weeks.

We’ll start with a tame Tetromino Minesweepers. I first saw this variant in Thomas Snyder’s old blog but I think there might have been earlier ones elsewhere. I’d love to know the history if anyone out there knows.

Tetromino Minesweepers: Place the 7 tetromino shapes into the grid; the shapes may be rotated but cannot be reflected. The numbers in the grid indicate how many of the adjacent cells (including diagonally adjacent cells) contain pieces of the tetrominoes. The tetrominoes cannot sit on the given numbers, and cannot touch even other, not even diagonally.