I like spending a day on one-off Processing "sketches," and might try to do at least one of those per month. It's possible "doodle" would be a more appropriate term for how I approach each exercise. When I doodle on paper, I make a kind of game with it's own rules and just see what the resulting outcome of those rules will be, usually some kind of abstract pattern. This time I was theorizing that a series of progressively expanding concentric circles would create the effect of flying through a tunnel. I placed the center of the tunnel on the mouse location so you could control the "direction" of the tunnel, and added some progressive line weight effect to supplement. I think it mostly works, but there were several nuances I had to work in to make it so.