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.

productsudokupuz

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.

5pairsudokupuz

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.
tetromineseg.png

tetrominespuz

Stockpiling

8 months without any events?
What’s up?
Out of ideas?

Nope, the exact opposite!
Around 40(!) puzzles have been written but I still feel the big picture is not ready. Also when one idea reaches the editing process, a bigger idea just craves to be made. I promise exciting things are to come but I don’t want to give any dates yet.

Offline things; last year, I won the Sudoku Northern Championship ahead of a field of almost 100 solvers (though mostly novice). The event is happening again next weekend and a tough field is travelling from Bangkok for my scalp. Sinchai is coming as well and he’s probably going to win it – the guy finished 10th in the Sudoku GP, uh, here take my title.

In the meantime, I’ll get through some more Flashbacks, which are currently about 5 years behind.
Until then!

Jan Wins 2016 BRANDS Queen’s Cup

[Photos from the event courtesy of Thailand Crossword Game Association]

The annual BRANDS Crossword Game King’s Cup was moved from the capital to the province of Nonthaburi. Last weekend, hundreds gather at Central Westgate, a newly-built shopping complex which was just opened less than a year ago last August. The main event (Scrabble) attracted competitors from 20 countries. This year the narrative was more exciting than what the organizers hoped for.

fos-centralwestgate-05

Central Plaza Westgate was opened just last year

Before the event Pichai Limprasert, ranked 101st in the world (due to less opportunities to play in official matches), had collected seven (!) consecutive wins in national events throughout the season. The level at the top of Thailand’s Scrabble players is very narrow – which made this record previously unimaginable. Would he be the one to snatch the 31st King’s Cup from 3-time world champion, New Zealander Nigel Richards?

Every square inch of the hall was used to accommodate thousands of competitors

Every square inch of the hall was used to accommodate thousands of competitors

Another venue inside the mall

Crowds gather at other venues inside the mall

When the 29-round qualifying matches begun, Pichai looked like a champion in the making as he led the pack from round 2 to round 5. His dominance was briefly interrupted by Singaporean Ming Hui Wee for four rounds before Pichai reclaimed his lead. Pichai reigned supreme until the very end (round 9-28!) until finally succumbing to Nigel Richards in their round 29 encounter.

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Scrabble players compete in 29 qualifying rounds…

The main event: Scrabble Open Division

… but only two spots in the finals

The two qualified for a three-game playoff and traded one win each allowing a cinematic last game. Nigel won that 469-356 and defended the King’s Cup once again, pocketing a handsome $10,000 USD.

Nigel Richards (left) defends his King's Cup from a new challenger, Pichai Limprasert (right)

Nigel Richards (left) defends his King’s Cup from a new challenger, Pichai Limprasert (right)

The match extended to a third game

The match extended to a third game

For the last two years, the King’s and Queen’s Cups remained with their defending champions – but this was to change since Kota Morinishi, after getting a new job, was absent from this year’s tournament. Familiar international favourites include Jan Mrozowski (his 4th trip to Thailand), Yuhei Kusui (who won in 2012) and his compatriot Takuya Sugimoto, who is still looking for his first podium finish.

Like previous years, the prizes were donated by the Royal Family

Like previous years, the prizes were donated by the Royal Family

A new name struck fear among the competitors in Tiit Vunk who flew in from Estonia to have a go at winning the Cup. Once again, putting up the resistance is half the Thai national team; Sinchai Rungsangrattanakul (who won in 2010) and Supachai Thongsawang (who came 3rd twice in 2014-15).

Jan Mrozowski, his 4th time in Thailand

Jan Mrozowski, his 4th time in Thailand

Yuhei Kusui was the last holder of the Queen's Cup in 2012, before Kota's three-year reign (2013-2015)

Yuhei Kusui was the last holder of the Queen’s Cup in 2012, before Kota’s three-year reign (2013-2015)

Sinchai Rungsangrattanakul, looking for his 2nd win

Sinchai Rungsangrattanakul, looking for his 2nd win

Newcomer, Tiit Vunk

Newcomer, Tiit Vunk

The format of 6 qualifying rounds provided little drama and 4 names quickly distanced themselves away from the field to secure spots in the final 5; Jan, Tiit, Sinchai and Takuya. Only Supachai and Yuhei had realistic chances to earn the 5th seat in the finals. When the preliminaries were over it was Yuhei who remain in the fight for the 10th Sudoku Queen’s Cup.

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2016 finalists: Takuya, Sinchai, Tiit, Jan and Yuhei

Ready..set.. go!

Ready..set.. go!

The finals consisted of 4 basic variants to be solved on stage. After three years of getting used to the whiteboard, Jan Mrozowski finished all four puzzles, just 21 seconds before Sinchai, and is rewarded with $5000 USD. Tiit Vunk earned the bronze medal despite having 4 errors in the Irregular Sudoku. The two Japanese finalists had uncompleted grids and finish 4th (Takuya) and 5th (Yuhei).

In action

In action

Jan Mrozowski adds another title to his name

Jan Mrozowski adds another title to his name

Sounds like a fun weekend to me!

Previous winners of the BRANDS Queen’s Cup
2007 – Chatchakarn Roongsiri
2008 – Panupol Sujjayakorn
2009 – John Robert Valcos
2010 – Sinchai Rungsangrattanakul
2011 – Poramet Yosamornsoontorn
2012 – Yuhei Kusui
2013 – Kota Morinishi
2014 – Kota Morinishi
2015 – Kota Morinishi

Only Kota has won more than once. Runners-up have included Rishi Puri (on multiple occasions) and well-known Chinese author and solver Chen Cen (2010).

Flashback #16 – Akasuke

The last puzzle in this series of Flashbacks is the hardest of the lot. Only 1 solver (Thomas Snyder) managed to solve it. Nowadays I use a computer when writing a difficult puzzle with many deduction-paths, but back then it was all grid paper and a lot of erasing. Because of the very-restricting nature of the type, I don’t think Akasuke will see any of its siblings soon.

So here is the devil that hardly anyone solved. Have another go at this in an untimed environment.

Akasuke: Fill in the grid of shaded cells with the listed numbers. Afterwards, the numbers become Akari clues, which are used to solve Akari in the usual manner.

akasukeegfb
akasukefb

Flashback #15 – Searchdoku

Searchdoku is credited to Dave Tuller in his AARP Wordsearches book. The back story of this puzzle was shared in the LMI forum. The original puzzle had a Maori-birds theme and because of the Maori language’s vowel-heavy nature, it ended up being difficult and too guess-y. This last-minute product below, finished just hours before the test was to start, was a gem.

When a puzzle is garnished with compliments, including one from logic puzzle-jesus Thomas Snyder, it means a lot to any puzzle constructor. But what excited me the most was that it got me writing for Akil Oyunlari for the next 4 years. That morning is vividly etched into my mind; I woke up late in the morning to read my e-mails. One of which was from Serkan Yurekli, who invited me to write a Searchdoku for issue 72 – which also had a similar concept.

Here is the puzzle below, can you see the break-in?

Searchdoku: Find the listed word in the grid going in any straight direction. Some words may be found in, or going through, the blank 9×9 grid. After several letters are filled in, the empty 9×9 grid becomes a Sudoku puzzle using 9 different letters.

searchdokufb

Flashback #14 – LITS2

LITS^2 is possibly my only creation that has caught on. There aren’t many LITS variations, let alone five years ago. The idea of cramming two pieces in each region proved to be a success as several other authors are now writing their own LITS^2.

The puzzle in the online test had a simple LMI theme. I recall tweaking for hours to get rid of that notch on the “M” – but gave up when the deadline was approaching.

LITS^2: Shade in two tetromino pieces in each bolded region. The two pieces in the same bolded region may not be adjacent to each other. Otherwise, standard LITS rules apply.

lits2egfb
lits2fb

Flashback #13 – Kropkuro

A big milestone for me has to be Puzzle Fusion, which was held during the early days of LMI back in the end of 2011. I still remember the frustration of tossing piles and piles of scrambled-up grid paper until every corner of my room was slowly drowning in litter. I completely underestimated how hard it would be to write this 24-puzzle test.
puzzlefusionlogo

The concept was two puzzle types combining to get a hybrid type. There were 8 sets of combinations and most of the solvers’ ratings were for the hybrids. The first hybrid was Kropkuro. Please correct me if I’m wrong, but I believe this was Kropkuro’s first appearance –before it started popping up in several European tests and most recently in Matus Deminger’s Kakuro contest.

I was still new to constructing and Puzzle Fusion ended up with a really poor balance of difficulty-spread among the puzzles. The Kropkuro ended up being too massive for such a test but as a stand-alone, I’m sure it is still enjoyable to solve.
Go get it!

Kropkuro – Fill in the grid with numbers 1-9 so that each number adds up to the given sum for that row or column. No number may repeat within a single entry. A white dot is given when the two neighbouring cells contain consecutive digits. A black dot separates two numbers where one is twice the other. 1 and 2 may be separated by any coloured dot. All dots are given.

kropkuro

LMI, November 2011