void move() {
    super.move();
    deltaV = -m_gravity * m_time;
    m_Vy += deltaV;
    println(deltaV);
    m_y -= m_Vy*m_time;
    if (m_y > m_groundPos) {
      m_y = m_groundPos;
      m_Vy= random(50, 80);
    }
  }