Part 1 of a "Two fer" in Honour of IPP35 - Hemi-spheres Puzzle

Hemi-spheres puzzle - looks simple doesn't it?

Last year was my first ever attendance at the international puzzle party and I had the most amazing time finally meeting puzzle friends from all over the world. I dragged the present Mrs S with me and she had a good time too (even if it was non-puzzling) - I was very proud that there were barely any Whack! Ouch! episodes at all (except when she discovered how much I had spent!) This year the IPP is, at this very moment, being held in Ottawa and unfortunately I could not afford to go and had to pull out at the last moment before the booking deadline. I was absolutely gutted and I miss all my friends dreadfully.

I know that at least 3 of the puzzle bloggers are out there just now and so the reading matter for those of you who are also unable to attend will have been a bit sparse. So today, I am giving you a “twofer” to make up for it! Yes it’s going to be two blog posts today instead of my usual one. The first (this one) will be my usual regular affordable and easy to obtain puzzle and the next will be a really special puzzle which is more expensive and much harder to come by. The second puzzle is actually an entrant in the 2015 IPP design competition and I don't want to spoil the entrant's chances of winning by publishing my own review too early. The judging should all be done by 18:00 Ottawa time which will be 23:00 here in the UK (BST) and so the second part of the "two fer" will be published at that time.

This is one of my alternate weeks so I have to start with an affordable puzzle for you. Again I am dipping in to my disentanglements from Tomas Linden’s Sloyd webstore. This puzzle is a real treat which I enjoyed immensely. The Hemi-spheres puzzle from Eureka puzzles in their Mini string range is very affordable at €5.04 and nicely packaged in a small dark green box. It was designed by Bernhard Wiezorke (whom I have never heard of before but I plan to keep my eye out for him in future). The difficulty rating on the box is 3 stars out of 4 (although as far as I can see there are no 4 star puzzles in this range) and I actually think it might be a bit simpler than that rating - maybe a 2½. Removing it from the box reveals a complete loop of a good quality string, a wooden ring on one end which has a strange loop of the string through it - I guessed that this odd looping must be important in the solve process. In the middle is a brown wooden sphere with the string entirely passed through the centre and at the other end to the loop is a nice pair of maple hemispheres pointing away from each other.

Stretched out lengthways the puzzle is 29cm long and 3.5cm wide but it rolls up nice and compact into a pocket or into the small green box. I did think initially that they had provided a solution leaflet but it is just an advert showing other puzzles made by Eureka. I doubt whether you will need a solution unless you are an absolute beginner but if you want one then it can be downloaded from Puzzle Master here.

The aim of this puzzle is not to remove anything from the string (in fact a basic knowledge of topology tells you that total removal is impossible) - the task diagrammed on the box is to rearrange the pieces such that the hemispheres are turned around and facing each other to make a complete sphere. Initially you would think that one hemisphere would need to just be pushed over the length of the string and over to the other side but obviously this is completely impossible. The string is completely free and able to rotate through all the pieces and loops can be pulled through and manipulated as you see fit. I am always petrified with these puzzles that I will just end up with a huge knot and then be unable to return it to the beginning let alone to solve it. I hesitantly made some moves and realised that there is actually very little that you can actually do. I suspect that it might be quite difficult to make it badly knotted without doing something really silly.

My eye and thoughts were obviously drawn to the loops around the ring - they must be like that for a reason and MUST have a use. Within about 10 minutes I was very surprised to have this:

Look! Hemi-spheres forming a complete sphere!

It’s not a particularly simple sequence that is required but I think I found it so quickly because there are actually not many moves that are possible. I quickly returned it to the beginning and decided to take it to work with me the following day. On a Monday I anaesthetise for a vascular surgeon and the staff in that operating theatre really love playing with my toys! Even the surgeons will play whilst I’m anaesthetising one of the more high risk complex patients and taking some time to do it. So when one of the support workers asked for a new toy to play with, I handed him this with a dire warning that if he got it in a knot then he either had to get it out of the knot or he would find it embedded in a body cavity without the benefit of anaesthesia! Just a paralysing agent would allow me to achieve what he deserved! With a vague look of concern he took it away and fiddled for an hour or so on and off. I think my threat of surgical violence upon his person may have inhibited him because he got nowhere and seemed to be trying the same move over and over again. Eventually he gave up and asked me to show him the secret. At this point I found that I couldn't find the second part of the sequence and he was greatly amused to see me effing and blinding whilst trying to find it. Eventually I did find it and was able to show it to him as a nice sequence much to his amazement. He admitted that he would never have done that.

I think that this puzzle is a lovely cheap little diversion which will not take any experienced disentanglers long but will really stump a child or a newbie for a while. It is very cheap and well worth a play. Go over to Tomas at Sloyd and see whether there is anything else you fancy.

The second part of the "two fer" will be published later this evening - I'll see you then!