A meditative state. You are experiencing Zen when you are completely focused on only one activity. Buddhist monks focus on their breathing in order to clear their mind of all distractions. This meditative experience is common across most Eastern cultures, in various forms. However, in Western cultures, it is rare for individuals to slow down long enough to un-clutter their minds. When it does happen, we typically call it "Flow."
In the Zentangle method of drawing, a "Tangle" simply refers to an organic, complex pattern or doodle. There are many standard patterns that an artist can learn, or you can feel free to make up your own patterns as you go!
Created with an image by TeroVesalainen - "success goal target"