Category Archives: Puzzles

Puzzle 172: Ring-ring

Here’s a little Ring-ring puzzle I made when testing that a bug in pzprjs was really fixed. [] [].

An unsolved 9x9 Ring-ring grid.Rules Fill the empty cells of the grid by drawing rectangles that consist of horizontal and vertical lines between cell centers. The sides of different rectangles may intersect but not overlap. Rectangles can’t touch otherwise; in particular, they can’t touch by a corner.

Announcing, a.k.a. Puzzle 169: Angle Loop

Here’s another Angle Loop, and you can solve it on the new

(You might want to try the example first: is a clone/fork of the excellent, a puzzle solving site and applet built by Daisuke Kobayashi. It seems the author has moved on, so when I wanted pzv support for some angle loops of mine, I decided to go ahead and fork the project. I’m hoping will be updated again and would be happy for my changes to make it upstream! I’ll be putting effort into separating the changes useful for upstream from site-specific changes.

For most puzzle types you can move them from one site to the other by switching between and in the URLs.


There are three new puzzle types: Besides Angle Loop, there is Heyawacky which slightly generalizes Heyawake by allowing non-rectangular rules. And Nurimisaki is a type that was quite popular on the Japanese puzzle twitter this year, where it was shared using the Kurotto applet. I hope to post some example puzzles for the other types soon. The additions compared to are shown in the “Added puzzles” tab in the type list.

The second major change is that… links? come with “rich link preview”, or whatever you want to call it.


I intend to keep updating this with new puzzle types and fixes as I need them, but I’m also happy to accept contributions. I would be particularly grateful for help in keeping the project Japanese: Some of the changes I’ve made so far are lacking Japanese translations, so please let me know if you can help with that.

If you have a bug report or want to submit some changes, head on over to github: robx/pzpr-puzzlink for the site, or more likely robx/pzprjs for the puzzle applet itself.

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!