unicursal to be called those figures can be drawn without lifting the pencil from the paper and without repeating the same line twice. For example:
We've all spent hours and hours of our childhood (especially in math class) trying to build, so by now everyone knows that one of them can be (which?) and the other not.
But there are others, such as these:
can you tell me which of them are unicursal and which not? The solution, as always in the comments or in a nice story by Euler in a few days.
