var radius = width; var circleHue = 0; var drawGradient = function() { circleHue ++; for (var r = radius; r > 0; --r) { fill(circleHue , 90, 90); ellipse(200, 200, r, r); circleHue = (circleHue + 1) % 313; } }; var draw = function() { colorMode(HSB, 360, 100, 100); noStroke(); frameRate(15); background(0); drawGradient(); fill(123); };