int s = 50;

void setup() {
  size(200, 200);
  rectMode(CENTER);
}

void draw() {
  background(255);
  
  if (mouseY < height / 2) {
    ellipse(mouseX, mouseY, s, s);
  }
  else {
    rect(mouseX, mouseY, s, s);
  }
  
  
  // Variation 1
  if (mouseX < width / 2) {
    s = 50;
  }
  else {
    s = 75;
  }
  
}