Radial Gradient

/**
 * Radial Gradient. 
 * 
 * Draws a series of concentric circles to create a gradient 
 * from one color to another.
 */

int dim;

void setup() {
    size(640, 360);
    dim = width / 2;
    background(0);
    colorMode(HSB, 360, 100, 100);
    noStroke();
    ellipseMode(RADIUS);
    frameRate(1);
}

void draw() {
    background(0);

    for (int x = 0; x <= width; x += dim) {
        drawGradient(x, height / 2);
    } 
}

void drawGradient(float x, float y) {
    int radius = dim / 2;
    float h = random(0, 360);

    for (int r = radius; r > 0; --r) {
        fill(h, 90, 90);
        ellipse(x, y, r, r);

        // still need this change: C++ float modulo
        h = fmod(h + 1, 360);
    }
}