float theta = 0.0;
float speed = 0.03;

void setup() {
  size(400, 400);
}

void draw() {
  theta += speed;

  background(204);
  
  // blades
  pushMatrix();
  translate(200, 200);
  rotate(theta);
  ellipse(0, 0, 35, 300);
  rotate(PI/2);
  ellipse(0, 0, 35, 300);
  popMatrix();

  // center
  ellipse(200, 200, 50, 50);
}