/**
 * An interactive hypnotic rectangle.
 *
 * <p>Elie Zananiri<br>
 * CART 253, Winter 2008</p>
 */
 
void setup() {
  size(400, 400);
  rectMode(CENTER);
  noStroke();
}

void draw() {
  boolean mode = true;
  float offset = min(1.0, max(0.01, mouseX/(width*1.0)));
  for (float i=1.0; i > 0; i -= offset) {
    hypnoRect(i, mode);
    mode = !mode;
  }
}

void hypnoRect(float ratio, boolean mode) {
  // draw the middle rectangle
  fill(mode?0:255);
  rect(width/2, height/2, width*ratio, height*ratio);
  
  // draw the corner rectangles
  fill(mode?255:0);
  rect(width*1/4, height*1/4, width*ratio/2, height*ratio/2);
  rect(width*1/4, height*3/4, width*ratio/2, height*ratio/2);
  rect(width*3/4, height*3/4, width*ratio/2, height*ratio/2);
  rect(width*3/4, height*1/4, width*ratio/2, height*ratio/2); 
}