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Concerning the coloured circles such as this: 

 

Difficulty:  Green   =  Easy

                     Yellow  =  Intermediate

                     Red        =  Challenging

The number in the circle is the most moves black can delay checkmate.  In this case white 

mates in five moves and the

diffiuculty is intermediate .

 

The solutions

are presented

in chess notation

where the square

is according to the

grid and the symbols as follows.

 

+ = check ; ++ = double check

x = captures; xx = checkmate