ps.</li>
      <li>Planets are solid-colored.</li>
    </ul>
    
    <h3>Version 4 - March 22, 2016</h3>
    <ul>
      <li>Enemy ships fly and fire towards player.</li>
      <li>Player has a shield that blocks missiles.</li>
      <li>Shield consumes energy. Energy recharges when shield is off.</li>
      <li>Multiple enemies appear at once.</li>
      <li>Player can switch targets.</li>
    </ul>
      
    <h3>Version 3 - March 4, 2016</h3>
    <ul>
      <li>Enemy ship fires seeker missiles at random.