September 30, 2009

Cast Equa and The Fifth Chair

After I got back from Costa Rica, I headed down to Eureka to pick up a few more puzzles. David, the owner was there, which is always nice because he tends to have good recommendations. I told him that I was thinking about picking up another Hanayama, and he suggested that I give Cast Equa a try. It was one of the newer puzzles from Hanayama, designed by Oskar van Deventer, and was supposed to be quite challenging.

We chatted for a bit and he mentioned that the person who designed Thinkfun's Aha! The Fifth Chair had stopped by the shop yesterday. David said that it was not too difficult but was an interesting little puzzle. I decided to purchase both Equa and The Fifth Chair and headed back home to try them out.

The Fifth Chair first is an assembly puzzle where the objective is to use the four chair-shaped objects to create a larger fifth chair that has the same proportions of the smaller chairs. This is an interesting puzzle because each incrementally larger chair has double the volume of the previous chair. So you are given two small chair (volume of 1 unit, lets say), one medium chair (volume of 2 units), and one large chair (volume of 4 units).  The resulting chair has the same proportions and will have a volume of 8 units (1+1+2+4).

I played around with this one for few minutes and wasn't making much progress. Eventually I took a somewhat more logical approach using the idea that the proportions should be the same, which ended up working. I like puzzles where a logical approach is effective because I find it more satisfying than just fiddling with something until it randomly works out, so bonus points for that.

Next I tried Cast Equa. It is a good looking puzzle that has a nice symmetry to it. The central spherical shape can rotate on the two posts sticking out of the ends of it. It is not immediately obvious how to even approach this one: I played around with it for about an hour and didn't have much luck. I found a few 'moves' but they didn't seem to get me anywhere productive.

I worked on this one on and off for a week or two and was really getting frustrated. Eventually I finally got it apart while sitting around waiting for a doctor's appointment. This was really exciting, but I was stumped as to what I did differently: I was just doing one of the moves that I had done before and all of a sudden it worked!

After studying it for a bit, I finally figured out what had happened. I can't say much more without giving away a hint at the solution. I think that the solution was a bit too tricky for my taste: it would have been appropriately difficult if the solution was just slightly more apparent, but that is just a matter of personal preference. Be prepared to spend some serious time with this one if you attempt it! Check out Oli's review of Cast Equa here.

Tomorrow I'll talk about some puzzles that I won in a raffle over at Eagle's Woodworking Forum.


  1. You know I have never tried to solve "The Fifth Chair"! But I should get one. You might enjoy a related puzzle which is much harder, my "Nine Bed Nightmare". You can make it using 125 livecubes.

  2. Nice! I had seen it on your website before. I like any puzzle that I can make with LiveCubes. I'll give it a try tonight.

  3. This puzzle is killing me! I figured out the first move, but im stumped!

  4. Yeah, this one is very, very difficult. Keep at it and you'll eventually discover some more moves. (Or go insane)

  5. freakin casta freakin equa! i want to throw it across the room and melt it down. i hate puzzles.

  6. i agree! i wish a hammer would break it! i want to pull the hairs out of my head its so frusrating ugh ugh ugh whover plays puzzles have no life. grrrr

  7. I just started Equa yesterday and have a feeling I'll be fiddling with it for a while. REALLY cool looking puzzle though!


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