function rectCollision(x1, y1, w1, h1, x2, y2, w2, h2) {
  // verifica colisão de retangulos
  return (
    (x1 + w1 >= x2) &&
    (x1 <= x2 + w2) &&
    (y1 + h1 >= y2) &&
    (y1 <= y2 + h2) 
  );  
}