int i;
float angle = 0.0;
int direction;

void setup()
{
  size(300, 300);
  direction = 1;
}

int colorR=255;
int colorG=255;
int colorB=255;

void loop()
{
  background(colorR, colorG, colorB);
  //translate(width/2, height/2, 0);
  //rotateY(angle);
  line(0, i, 300, i);
  line(i, 0, i, 300);
  line(0, 300-i, 300, 300-i);
  line(300-i, 0, 300-i, 300);
  fill(255, 0,0);
  ellipse(i+2, i+2, 30, 30);

  fill(0, 0, 255);
  ellipse(300-i-2-30, 300-i-2-30, 30, 30);

  fill(0, 255,0);
  ellipse(300-i-2-30, i+2, 30, 30);

  fill(255, 0, 255);
  ellipse(i+2, 300-i-2-30, 30, 30);

  if (i >= 140 && i <= 150) {
    if (i % 2 == 0) {
      fill(255, 0, 255);
      ellipse(100, 100, 100, 100);
    }
  }

  i += direction;
  angle += 0.01;

  if (angle > TWO_PI) {
    angle = 0.0;
  }

  if (colorR <= 0) {
    colorR = 255;
    colorG = 255;
    colorB = 255;
  }
  if (i > 300 || i < 0) {
    colorR -= 30;
    colorG -= 30;
    colorB -= 30;
    direction = -1 * direction;
  }
}