In the illustration, we have eight toadstools, with white frogs on $1$ and $3$ and black frogs on $6$ and $8.$ The puzzle is to move one frog at a time, in any order, along one of the straight lines from toadstool to toadstool, until they have exchanged places, the white frogs being left on $6$ and $8$ and the black ones on $1$ and $3.$ If you use four counters on a simple diagram, you will find this quite easy, but it is a little more puzzling to do it in only seven plays, any number of successive moves by one frog counting as one play. Of course, more than one frog cannot be on a toadstool at the same time.
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