This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

Recursion.

A demonstration of recursion, which means functions call themselves. Notice how the drawCircle() function calls itself at the end of its block. It continues to do this until the variable "level" is equal to 1.

 
void setup() {
  size(640, 360);
  noStroke();
  noLoop();
}

void draw() {
  drawCircle(width/2, 280, 6);
}

void drawCircle(int x, int radius, int level) {                    
  float tt = 126 * level/4.0;
  fill(tt);
  ellipse(x, height/2, radius*2, radius*2);      
  if(level > 1) {
    level = level - 1;
    drawCircle(x - radius/2, radius/2, level);
    drawCircle(x + radius/2, radius/2, level);
  }
}