Trig Function Art
Based on the heat map from: http://geogebrart.weebly.com/blog/heat-map.
Try playing with the trig functions and see how that affects the results.
f(x, y) affects the size of the circles.
g(x, y) affects the red color.
h(x, y) affects the green color.
i(x, y) affects the blue color.
j(x, y) affects the transparency.