Zen Tangling?

Have you heard of this before?  Turns out it is something I have been doing for a long time but didn't know it had a name.  Go figure.

I  have done it when I am very bored and have nothing else to do.  It does work perfectly in an airplane to pass the time and tune out fellow passengers.  So I guess it is relaxing.  I can get so engrossed in it that I don't notice if anyone even watches.  Sometimes I will color in specific parts but mostly just use a black marker on white paper.  Usually I have thrown them out but perhaps I should keep them?  Maybe they are little works or art!