I'm not happy with the composition on this one. It's not well-designed and there are several awkward overlaps in there that flatten it out. Bleh.
As an excuse I offer there was not much time to work on this, although such simple illustrative concepts should be second nature by now. Ah, well. Here is the original quick sketch: (Don't blother clicking on it, it doesn't get any bigger...)
I doodled it quickly on paper and then held it up to the camera on the iMac, and then drew on top of that in Photoshop!