2/16/13

Questions and Answers

Whenever I get a new puzzle like this one, besides trying to solve it I like to figure out how complicated it is. What moves? What changes? What stays the same? How difficult is it? And so on. 

Can All 8 Squares Be Switched Around?
The answer is that eight squares can all be moved to any position, but not in all possible ways. In other words, it is possible for each of the 8 squares to be on any corner or anywhere in the interior of the original 2-by-4 shape. But if you look carefully at the puzzle, you will notice that each square is always attached to the same 2 neighbors no matter hoe many times it is moved. In effect, the 8 squares form a necklace held together with the thin cords. This is why the squares cannot be moved to all positions in all possible combinations.

Can the 8 Squares Be Rotated?
The answer is that all the squares can be rotated, but there are restrictions on the combinations of rotations that can occur. In other words, the design on a square can point in four different several others at the same time.

Can the Squares Be Turned Over?
The answer is so, unless all 8 squares are flipped. There are 2 sides to the puzzle, as you can see when it is first opened. One side has the design that forms the3 separate ovals. The other has the design that forms the 3 interlocked ovals of the solution. It is not possible to get a “mixed” design on the 2-by-4 shape.


What Shapes Can’t Be Made?
One of the first things I tried to do with this puzzle after solving it was to make a flat window shape.


After considerable unsuccessful effort I decided to try to figure out whether or not it was even possible to make this shape. It turns out to be impossible, and I could have saved myself a lot of wasted effort if I had known this ahead of time. There is enough frustration with these puzzles without trying to do things that are impossible.

I know from experience that I cannot claim that something cannot be done in a puzzle solution book without backing it up, so I will give a brief explanation.


In this illustration, the number in the upper left corner of each square is the number of cords in each groove on the square. The number in the lower right is the number of the square. Starting at number 1 let’s travel to all 8 squares and back to number 1. If we make a right turn through a square with 4 cords, let’s add 1. If we make a left turn through a square with 4 cords, let’s subtract 1. If we make a light turn through a square with 2 cords, let’s subtract 1. If we make a left turn through a square with 2 cords, let’s add 1. If we go straight, let’s add 0. The numbers in the centers of the squares are the values we get by traveling around the square in this way. Notice that they add to 0, no matter how we might change the shape of the puzzle by making moves.

If we do the same calculation on the window shape, we get a total of 4! Therefore, the window shape cannot we made. You can use this method to decide if other shapes can be made. If you find this kind of thing interesting, try to figure out the effect of “flaps” on the method.

How Difficult Is It to Solve?
A quick answer here is that the puzzle is easier than Rubik’s Cube, but the many possible shapes make it more interesting to play (or work) with.

One way to gauge difficulty is to try to count the number of possible arrangements and shapes. There are 43 quintillion possible arrangements of Rubik’s Cube. In the case of Rubik’s Magic, there is no obvious definition of what makes shapes different. Since the puzzle can be moved gradually to make slightly different shapes, it may make sense to just say there are infinitely many shapes possible.

Nevertheless, one way of counting possible shapes is based on the number of right turns, left turns, and flaps—similar to the method used to decide if a shape is possible (see page 18). This method ignores the geometric shape, mirror images, the position of the cords, the design, and whether the shape is turned inside out. There are no more than 1,351 possible shapes, counted this way, and only 59 of these do not have flaps.

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