This applet shows another powerful, and cheap, graphics tool-- blurring. By nature, computers want to produce sharp, crisp shapes; but the natural world is filled with smooth curves. Blurring makes sharp shapes smooth.
Blurring is easy to accomplish-- replace each pixel with the average value of its neighbors. By taking a weighted average, and weighting the center pixel more, you can accomplish a weaker blur; or by averaging more pixels, you can get a stronger blur.
In this demo, the pixels at the center blur; but the edges do not. The top and left edges animate, just to keep things interesting. The color thus flows in from the edges.
Link to the source code.