Blind string challenge. This tile was begun with a blind string. I placed my pencil at the edge of the tile, closed my eyes and went for it. It was not what I wanted. It left too much white space. But that was the challenge so I just accepted it and thought about ways to "make it work!"
I enhanced the string with a blue colored pencil so you could see what I had to work with. And, after a day or so of looking at it, I got some ideas of what I wanted to do with it. I think that is the beauty of doing the Zentangle challenges. It keeps encouraging me to stretch my creativity.