int count = 0;

void setup() {
  frameRate(2); // Try changing to 10
}

void draw() {
  background(120);
  if (count % 2 == 0) {
    // Try changing 2 to 5
    ellipseMode(CORNER); // Try removing
    fill(255, 0, 0);
    rect(20, 30, 40, 40);
    fill(0, 255, 0);
    ellipse(20, 30, 40, 40);
  }
  count = count + 1;
}