@HG, In the context of my before the previous example I think the ":" symbol does not influence the preset although it works fine in the interactive diagram!
I finally had time to look at this. The preset as it was indeed ordered completely random shuffling of Y and W. Which means that YY-WW or YW-YW is also a possible outcome. The way the shufflespecs work in the preset is that the second element of the triplet specidies the set of pieces that have to remain symmetrically located, and the third element specifies the set of pieces that must be equidistributed over square shades. A 0 there means there are no such pieces (and if both are non-zero, the third element is ignored). The first element then contains the remaining pieces, and must be non-empty.
By putting (W Y) in the first element, you asked for an unrestricted shuffle. Because the first element must not be empty, you have to put one of the two there (say Y). The other (W) can then go into the second element, and will be symmetrically shuffled (either as W.-.W or as .W-W.). The Y will then be 'shuffled' over the remaining open spaces, which in this case is just placement there as there is nothing left to choose.
I am not sure why the automatic generation did not work; I haven't looked yet what shuffle string you specified there. Perhaps it failed to put one of the Y, W in the first element, and put them both in the second. Anyway, try if this works:
set shufflespecs (
(Q V U) // shuffleset
0
0
(I M) // shuffleset
0
0
(Y) // shuffleset
(W)
0
0 // mirror to get black
);
I finally had time to look at this. The preset as it was indeed ordered completely random shuffling of Y and W. Which means that YY-WW or YW-YW is also a possible outcome. The way the shufflespecs work in the preset is that the second element of the triplet specidies the set of pieces that have to remain symmetrically located, and the third element specifies the set of pieces that must be equidistributed over square shades. A 0 there means there are no such pieces (and if both are non-zero, the third element is ignored). The first element then contains the remaining pieces, and must be non-empty.
By putting (W Y) in the first element, you asked for an unrestricted shuffle. Because the first element must not be empty, you have to put one of the two there (say Y). The other (W) can then go into the second element, and will be symmetrically shuffled (either as W.-.W or as .W-W.). The Y will then be 'shuffled' over the remaining open spaces, which in this case is just placement there as there is nothing left to choose.
I am not sure why the automatic generation did not work; I haven't looked yet what shuffle string you specified there. Perhaps it failed to put one of the Y, W in the first element, and put them both in the second. Anyway, try if this works: