Engagement Wishes To A Friend

Because of my new work commitments , I am forced to temporarily shut down this site. Writing about mathematics

requires an effort that I now see myself not able to perform. The lack of time, in fact, was what caused the unfortunate mistake a few weeks ago.
So, I can not weigh seen the blog as I'd like, Bourbaki is closed until further notice.

Many thanks to all that you have me followed during these two years.

Slogan Eating Disorder

unicursal

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.