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"Solo chess" broken link
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Someone did not enable the feature before the feature was announced. The joys of IT chaos. 
(Source: I have done IT work for 20 years)
it's fixed
Oct 27, 2017
0
#7
Novel idea involving some planning ahead!
There seems to be a bit of a problem with alternative solutions. A couple of the level 5 examples had multiple solutions, but only one would be accepted. There is no information suggesting any one of the possible solutions would be preferable except to try them one by one.
Oct 27, 2017
0
#8
The first level 5 puzzle I tried must have been one of the ones only accepting a single solution. With only two queens remaining on the same file, neither could capture the other.
Oct 28, 2017
0
#9
Yes, then the only thing to do is backtrack.
As there seems no basis for preference of different alternate solutions, they should all be allowed.
Just got a message about some new feature called "solo chess" but the link is broken at present.