Category Archives: Puzzles

Puzzle 167: Dual loop

Here’s a new loop type. You can solve and check your answer over here. (Let me know if that works for you and is useful, very much work in progress.)

In other things:

  • I’ve worked on puzzle-draw a bit; there’s now an incomplete and experimental more generic input format, which should eventually allow you to draw graphics for non-hardcoded puzzle types. Including doing things like using other symbols instead of numbers where number clues are currently expected.
  • Be sure to take part in the Puzzle Grand Prix next weekend, authored by Jonas Gleim and me. There should be some nice puzzles in there. Check out the instruction booklet.
  • We’ve published a puzzle book via the German Logic Masters, with a chapter of Minesweeper puzzles by myself. There’s a number of prominent constructors involved! (It’s not really being marketed to expert puzzlers, which I suppose explains that the publisher doesn’t even bother to note the involvement of serial world champion Ulrich Voigt.) It’s claimed to be available already, though there’s some information it won’t ship before March. Have a look inside at or check it out at or

Finally here’s the puzzle:Rules Draw two loops that consist of horizontal and vertical segments. One loop goes along the grid lines, while the other loop goes from cell center to cell center. Clues indicate how many of the (up to) four adjacent edges have an intersection of both loops.


WPC 2018, graphs

While analyzing the WPC result for my review series (starting with WPC 2018 review, part 1), I made a couple of pretty graphs, which I’d like to share here. To make these, I scraped the result PDF into a spreadsheet; I hope it’s useful to you.

To start with, a visualization of my scores per round, relative to the 10th best score. This is what I based my analysis on. A very flat Thursday, peak for the Paths round, Friday afternoon dip and then a strong finish.

A graph of the ratio of my score to the 10th best score, round by round.

My score per round relative to 10th best

Next a couple of graphs of how the positions developed over the course of the tournament. As a base-line for each of these, I chose the sum of n-th best scores per round, for a suitable n. First you can see just how much stronger Ken Endo is than anyone else, then that things were more exciting behind him than the first graph shows. And finally a top 20+ graph.

A graph of the top 10 players at the 2018 WPC, round by round.

Top 10 relative to the sum of 5th best scores

A graph of the top 10 players at the 2018 WPC, round by round, with the exception of Ken Endo.

Same graph (relative to 10th best), but excluding Ken Endo

A graph of the top 20+ players except Ken Endo at the 2018 WPC, round by round.

Top 20+ without Ken, relative to 15th best

I’d love to see what else you can get out of the data!

WPC 2018 review, part 5

Welcome back, to the final episode packed with puzzles and drama. For the morning, we had the last two preliminary rounds on the schedule. By this time I knew where I was at: Around 14th place, which is a decent result for me relative to past performance. I managed to decide to be ok with it, particularly with not having come in to the competition in best shape.

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Puzzle 166: Inner ABC

Last one of the WPC preparation puzzles. This is a pretty cool type, but it’s not that easy to pull off – lots of potential to run into contradictions or non-uniqueness. It’s a bit of a confusing rule, but I feel that it works out very well.

An Inner ABC puzzle.Rules Fill the empty cells with letters ABC so that each row and column contains each letter exactly once. (Ignore the clue cells.) The clue cells then indicate all letters that can be seen from that cell in both horizontal and vertical directions. The dashed clue means that there is no common letter to be seen.

Or see the instruction booklet.

Puzzles 164 & 165: Stalagtites and Stalagmites

Two more preparation puzzles. This one is probably my favorite take on the “worm rule”, exhibited here for rows and columns without clues. While constructing, it felt like there might be more potential in the type if the order of stalagtites wasn’t given. (The clues here are all 3s and 4s, in case you have trouble deciphering the typesetting.)

Two Stalagtites and Stalagmites puzzles.Rules Fill the grid with numbers 1 to 5 so that they don’t repeat in rows or columns. The hints around the grid denote all the increasing or decreasing sequences longer than 2 in the given row/column in the correct order. The sequence is increasing from the tip of the sign.

Edit Fixed instructions again.

Or see the instruction booklet.