TUZ: Variation on a theme by Victor Vasarely

int NUM=3, NUM_CHANGE=2, a=32;
float P=26.0, t, w1, w2;

void setup() 
{
  size(600,600); frameRate(30); noFill(); 
  strokeWeight(5); stroke(255); smooth();
  ellipseMode(CENTER);
  t=0; w1=2*PI/P; w2=-PI/P;
}

void draw() 
{
  int i, j; t=t+1/30.0;
  if(t>P/2)
  {
    t=t-P/2;
    NUM=NUM+NUM_CHANGE;
    if(NUM*a>width*sqrt(2)){NUM_CHANGE=-2;}
    else if(NUM==3){NUM_CHANGE=+2;}
  }
  background(0);
  
  for(i=-NUM/2;i<=NUM/2;i++){
    for(j=-NUM/2;j<=NUM/2;j++){
      ellipse(width/2+i*a*sin(w1*t)+j*a*cos(w1*t),
              width/2+i*a*cos(w1*t)-j*a*sin(w1*t),
              .8*a, .8*a);
      ellipse(width/2+i*a*sin(w2*t)+j*a*cos(w2*t),
              width/2+i*a*cos(w2*t)-j*a*sin(w2*t), 
              .8*a, .8*a);       
    } 
  }
}