Puzzle 147: Skyscrapers Domino Construction

Here’s a puzzle that I made as a Christmas present.


Rules Place the given set of dominoes in the marked domino tiles. Whenever two dominoes touch by an edge, the adjacent numbers must be the same. Clues outside the grid are skyscraper clues: They indicate the number of visible skyscrapers when looking along the corresponding row or column from that point, where each number represents a skyscraper of that height. Skyscrapers are blocked from view by those of greater or equal height.

Puzzle set: Classic Sudokus, 2017 East Asia Sudoku Championship

Last Sunday, South Korea hosted the Asian Sudoku Championship in Seoul, which included a set of classic Sudokus that I wrote.

These originally came out of practicing my Sudoku construction skills by writing a puzzle a day for a long week early last year. It’s still a hit-or-miss process for me, but I think there were some nice ones. Solve on PZV (a b c d e f g h i) or find the set below.

In other news, don’t forget to take part in Puzzle Ramayan at LMI this weekend: A set of easyish classics and region puzzles that I prepared, including some instructionless variants.

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Puzzles 145, 146: Masyu

Towards the end of last year Grant Fikes ran a puzzle construction contest on his blog: instructions, results. With the aid of random.org, I managed to defend the title from the previous Logicsmith Exhibition, tied by score with Nikola Zivanovic.

The objective was to construct a 10×10 Masyu puzzle that leaves over a battle ship fleet of empty cells while minimizing the number of clues. That turned out to be quite a fun challenge, and led to some rather nice puzzles, which I didn’t quite expect. I was a bit worried the contest would be won by optimal computer-generated submissions, but it seems no one went to that effort. Instead, I’m left curious as to how close to the optimimum we got with 8+7 clues.

Here are my two submissions (rules).masyu-logicsmith-2(solve on pzv.jp)

masyu-logicsmith-4(solve on pzv.jp)

Puzzle 144: Easy as ABC (Zehnkampf)

Last weekend I took part in a puzzle decathlon, run by Berni of croco-puzzle. That involved 10 rounds modelled on the athletics decathlon, where the running events mapped to puzzle solving (the hurdles were possible broken puzzles), jumping events mapped to puzzle creation, and throwing events mapped to optimization puzzles. A lot of very original ideas, and overall it worked very well. Puzzles and results are available at logic-masters.de.

One of the construction rounds, the Pole Vault, gave you three tries at constructing a high-scoring Easy as ABC puzzle: Before each attempt, you chose a grid size, then had 15 minutes to extend a partially clued puzzle of that size to a correct puzzle. The score was calculated by subtracting twice the number of added outside clues, five times the number of inside clues and once the number of diagonal adjacencies in the solution from ten times the number of rows/columns. I had a rough start there, but ended up with a pretty good third try, with this 8 by 8 puzzle.


Rules Place letters A-C into the grid so that each letter occurs once in each row and column. Clues indicate the first letter in the corresponding row or column.

Puzzle set: 24 Hour Puzzle Marathon, 2016 edition

Took me a bit longer this year, but here’s my set for the 24 hours from April. I took a bit of a different approach this year, with four puzzles each of six more or less standard puzzle types. My hope was to make the round a bit more approachable than in previous years, though this may have been taking it a bit far. But I think the round worked out fine in the contest.

Individual puzzles below, or get the whole set in PDF: 2016-24h-rob-puzzles.

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Puzzle 143: Nanro Signpost

Here’s a Nanro Signpost.


Rules Shade some cells, so that all shaded cells are connected, and such that shaded cells don’t fill any 2×2 square. Clues indicated the number of shaded cells in an area; each area must have at least one shaded cell. Whenever two shaded cells touch across walls, the number of shaded cells within both areas must be different.

Puzzle 142: Statue Park

Here’s a Statue Park puzzle, with a full set of pentominoes. I made this one on the train back from the WPC in Senec, I still plan to post some thoughts on that some time.

In other news, I’ve been writing some puzzle sets for Nibbl (Android, iPhone). It’s an app that works as a solving interface and marketplace for handmade puzzles. See also Rohan’s announcement from earlier this year; the interface has been improved quite a bit since then. If you use my referral code ROBR9402 (or someone else’s), you’ll start with 100 credits, with which you should buy some of my star battle or skyscraper puzzles which came out pretty well.

I won’t stop posting here, though, don’t worry!


Rules Place a full set of twelve pentominoes in the grid. Different pentominoes must not touch along an edge; they may touch diagonally. Black circles must be part of pentominoes, white circles must not. All cells that are not part of the pentominoes must be connected by edge.