Sunday, 29 December 2019

I Just Don't Understand It!

Hanayama Cast Rotor
Today's post is going to be a quickie because 1) I don't have much solved to write about today and 2) I have been writing my New Year's Eve "Top puzzles of the year" post which has taken me quite a long time! The Hanayama Cast Rotor is the latest puzzle from the Hanayama company and continues its Huzzle series with an extremely difficult level 6 out of 6 challenge. My copy was bought from the UK based Nic Picot here but for those of you in the Americas, I would suggest buying it from PuzzleMaster here. It is great value for money like all of the Hanayama puzzles at approx $13USD/€9.50/£8.65.

This puzzle was designed by the amazing Kyoo Wong who also gave us the Cast U&U, Cast Delta and Cast Trinity. This puzzle, like many Hanayma puzzles, consists of 2 complex metal pieces (in this case they do appear to be identical) which need to be separated from each other. I personally categorise this puzzle as more of a Maze type puzzle than a Disentanglement. This is because a pathway through a pretty complex maze needs to be navigated to get the pieces into a position where the can just slide apart.

Two seemingly identical pieces
I am sure that you are wondering why my post is entitled "I Just Don't Understand It"? Well, let me tell you that I have managed to solve the puzzle just the once BUT there are 2 reasons for my Exclamation - firstly, I always maintain that a puzzle has to be understood to be truly solved and as a mark of this achievement, it is essential that it should be possible to repeat the task at will. It may require a fair bit of work to solve it each time but it should still be possible. I have managed to disassemble this puzzle twice now but cannot say that I know it well enough to do it at will every time and therefore I just "Don't understand it!". The second reason for my title is that in the 2019 IPP Design Competition this puzzle won a Jury Honourable Mention (I'll not dwell on the incorrect spelling they use of honourable on the results page!) I have to say that I cannot possibly understand how it won that prize. Most puzzlers spend a few hours each day of the IPP playing with the competition entries and usually only a short period on any one specific puzzle. I personally think that this puzzle is MUCH too difficult to have been solved by many people there to allow them to appreciate this as worthy of such an award.

Obviously, the puzzle won the award fair and square but I really don't understand it! I wonder whether someone had solved it and thereafter it had been left in a state near to the solution and hence people did not struggle with it as much as me? Or, much more likely, I am just showing off that I am really NOT terribly bright and my lack of understanding of this puzzle is just me being generally inadequate. I'll let you decide the truth of that - comment below......on second thoughts, please don't let me know how inadequate I am!

Right then, back to the puzzling experience...the Rotor consist of two 3 spoke wheels and the rim of the wheels have gaps in them between each spoke. The spokes are quite thick apart from 1 on each piece which has a groove engraved through it which is obviously there to allow the pieces to slide apart. It quickly becomes apparent that the gaps in the rim won't go across the groove unless the correct gap is used and it must be done in exactly the correct orientation. Very unhelpfully the pieces arrive with the pieces arranged so that they are 180º out in their orientation on each other and they must be manipulated so that they have been rotated into the correct orientation but also at the same time placed into the correct position at the same time. This is where the puzzle gets tough...only certain movements are possible at first and later other ones become available.

My problem here is that there is no way to keep track of what you are doing and no way to make a definite progression whilst being sure that that is what you are doing. It is a maze that almost changes as you solve it! I very quickly got lost and then was unable to backtrack to the beginning. I did start with the intentions of keeping track and even took a few basic notes but rapidly realised that I could not adequately describe on paper what I was doing and taking photos just produced dozens of identical-looking pictures. After a short while, I thought I had found a pattern but this just led me back to the beginning again and I needed to find something else to do outside of the pattern. I found a few things possible and followed them and promptly got lost - unable to return to the beginning. At this point, I was left trying lots and lots of random movements. I knew what I needed to achieve but none of the random movements allowed it to happen in a single move and yet more random moves were needed. Eventually, by pure chance, I recognised that the 180º move had occurred and then I needed to advance towards the correct position. After about 2 hours, with a little squeal of satisfaction, I separated the two pieces:

Finally! 2 Hours of random movements!
Mrs S looked up with annoyance at the noise (I'm surprised she tolerated the clinking noises, to be honest) and I was forced to admit that I had absolutely no idea how I had solved it!

OK! Time to put it back together. The entry can only be done one way and thereafter the maze needs to be negotiated. Another 2 hours and it was at the beginning...again, pure chance. I thought that maybe a second solve would help me understand it and I began again.

All I have to say is that I got it apart for a second time but have no real clue what the correct moves were to achieve it. I agree that this is a pretty tough puzzle, very worth its' 6/6 star difficulty rating (PuzzleMaster 10/10) but, unlike many of the other puzzles of this difficulty (in particular, the Cast Enigma - reviewed here) I found this one less than pleasing. For those of you who collect Hanayama puzzles then this is an essential purchase. For those of you who like to struggle for a long time then also buy this but if you just want a bit of fun then I'd look elsewhere.

I still do not understand how so many puzzlers at the IPP could have rated this so highly - maybe I am just terribly dim?

On New Year's Eve, I hope that you will join me on the blog for my summary of my top 10ish puzzles of the year! In the meantime, here are my top tens from 2018, 2017, 20162015 and 2014.


  1. Your point about being able to repeat a solve is well taken. Having good notes helps to retain that expertise. It is not very satisfying to just jiggle something apart. If I ever get my Cast Vortex back together (I've done a thorough analysis and I am making progress), I will attempt the Cast Rotor.

    1. Good luck! I look forward to hearing of your success!

  2. The judges have an impossible task. I don't see how anyone can evaluate 60+ puzzles and come up with "winners". The IPP attendees have the same problem, I do not remember ever even looking at this puzzle, but for that reason I did not vote for it. The process is not perfect, but I think the puzzles that win are some of the best. Everybody has different criterion for puzzles they like, so not everyone will agree on the best. It is still a lot of fun playing with all the puzzles (if you have time).

    1. I agree with you George! It is a very difficult task but I think they have access to the puzzles for a fairly long time. I do wonder whether their decision is made based on a knowledge from the solution sheets. Thus they make a decision based on the cleverness of the solution rather than the ability to discover the solution.

      As for the attendees, a puzzle like this would never win because the solution is to undiscoverable in the time anyone has.

    2. As an attendee, I often have the problem that I like a certain puzzle, but I cannot solve it. Do I look at the solution before deciding what to vote on? Also, if my first impression is not good, I will often skip a certain puzzle entirely (like Cast Rotor). But this means I never vote for a puzzle that I don't like right off the bat. This is sad because I'm sure many of the puzzles I would like don't have a good first impression. As I said, it's an imperfect system.

    3. I often wonder why the jury decision it’s very different from the attendees and I assume it is the time available to discover the nuances of each of the puzzles.

    4. Yeah, it is a fairly difficult and subjective task! I wish we had more time with the puzzles, in recent years the room has opened a day (or half-day) early and the judges have another day for judging. But that day is more like 5 hours before we start voting. So maybe 10-15 hours total.

      I've raised the idea of doing the jury voting closer to the awards banquet, but that has some issues with scheduling the time to meet and giving Nick time to create the presentation. I'm able to solve maybe 2/3 of them over the course of the party, but maybe only 1/3 by the time I have to vote. I do spend at least some time working on each of them to get an idea of what the solving experience is like, but if you do the math it is about 10-15 minutes per puzzle on average. I generally don't look at the solutions other than to confirm my solution or otherwise clarify something.

      I'd attribute the differences mainly to the fact that it is a small panel of people with their own preferences, compared to a larger group of attendees.

    5. Thanks for the explanation Brian. I look forward to meeting up at the next IPP.

  3. Hi there. Long-time reader of your blog but first time poster here.

    This made me think about what makes a good puzzle. Is it difficulty (this one), elegance (Cast Loop), the ability to subvert expectation (Cast News)…? As George said, this can be subjective. For me, I enjoy most puzzles that take a long time to understand, but physically can be solved fairly simply. One of my favourite is Cast Horseshoe. Despite being able to take it apart in a second, I still don’t fully appreciate exactly how it works!

    1. Indeed Michael, what makes a great puzzle? It is different for everyone but I would say there needs to be a certain amount of logical progression. The time taken is immaterial as long as there is logic and thought rather than pure randomness.

  4. We're a bit later now, and i wonder if you managed to find the logic in how to solve it every time ;).

    This one was one of the first ones i actually did, and other than one move, there wasn't much luck involved. In the end you can be in 4 parts of the maze, and figuring out which part and where to get is helped by the markings i've found. If they hadn't hidden a single move, it'd have been a 100% logical puzzle (and the place where you need to go is noticeable i found.

    Compare this to something like the Trinity, which is a lot more fiddly i find, and a lot less logical and blocked by minute details.

    1. No, I’ve never got to grips with it. In fact it remains in two pieces as I cannot put it back to the beginning again.I really dislike it as a puzzle. The problem is that it’s impossible to keep track of where you are or have been. I prefer the Trinity because at least you can tell what you have done before.

    2. It comes down to understanding which part of the maze you're in. There's basically 96 different moves you can do with the entire puzzle i think. But only half are relevant since it's divided in 4 parts. Using the parts as 2 gears which are tilted upwards in the middle, and the markings which face up and how they line up, can show you in which part you are. There's basically 4 positions which are important, which are the 4 states you can get in around the hidden crossover part. Finding that is a matter of doing a full circle, switch one piece, doing a full circle, switch the other piece, full circle, switch the first piece again, full cirlce, so 6x4 moves at maximum + a couple to get to being able to switch the other part again. And testing the other spokes if they are in the correct position.
      Always keep the colors on the same side though, if needed just flip the puzzle to keep the "gears" facing upwards.

      Not sure if that helps, but it's how i approached it. If someone scambled it up well, i can easily find my way to one of the 4 positions mentioned by doing the above, and get to one of the other positions leading towards the end or beginning.

      (I hope it's not too spoilerish, i tried to be a bit circumvent about it to not spoil people who wouldn't want the full solution.)

    3. Definitely not spoilerish! I might go back to it one day but for the moment I’m too fed up with it to try again. There are very few puzzles that I actively dislike but this seems to be one of them.

    4. First-time poster here! I'm in the opposite camp: this is my favorite Hanayama so far. (Granted, I've only done about ten of them.) I see where you're coming from, because the puzzle states are so hard to distinguish. I didn't start enjoying the puzzle until I found a compact notation for describing the moves and puzzle states.

      With the complete state map in front of me, I definitely can't say that the puzzle is simple. (There are 72 states in total.) It is, however, extremely logical. It's reducible to a pencil-and-paper puzzle of symbol manipulation, and the entire map can be constructed by following a few simple rules.

      In short, I found Rotor frustrating at first, but deeply satisfying to understand completely... which took me over 24 hours, spread over several days. The level 6 is well-deserved.

    5. Yet another person who loved it! Maybe I need to try again? It’s still in pieces on my desk!

      I’d be very interested to see your notation and state diagram.



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