void setup() {
  size(400, 400);
  fill(255, 64);
  frameRate(2);
}
void draw() {
  int num = fibonacciNum(frameCount);
  println(frameCount, num);
  rect(0,0,num, num);
  if(frameCount==14) frameCount = -1; // restart
}
int fibonacciNum(int n) {
  return (n < 2) ? n : fibonacciNum(n - 1) + fibonacciNum(n - 2);
}