Experiments with 'Brushes'

I was recently checking out a cover of the New Yorker illustrated by David Hockney and speculating on its medium. A short time later, a facebook friend posted a link to an article about Hockney, and his daily practice of drawing on his iphone, or ipad with the 'Brushes' application.

As a fairly new iphone user, I figured maybe I should give it a try...
Above are some of my experiments of the first week. Like photoshop, it's composed of layers-- but you're drawing with your fingertip on that 2 x 3ish" screen of your phone... it's some fun, and a good way to while away a long dark car drive, say (for the passenger anyway...)
The article with David Hockney is here.

P.S. you can see here that my predisposition towards certain colors is firmly entrenched, regardless of medium.