title: Centering div vertically and horizontally
body: <p>Is there any way to center <code>.polygon_container</code> and <code>.polygon</code> vertically and horizontally? Also is there a possibility to make the size of it responsive like the <code>&lt;img&gt;</code> tag below? </p>
  
  <p><a href="http://cichyone.linuxpl.eu/ranestwen/ex/" rel="nofollow noreferrer">http://cichyone.linuxpl.eu/ranestwen/ex/</a></p>
  
  <p>I've tried text-align, margin auto etc and nothing works.</p>
  
  <p>When I set it in the middle using <code>margin-left</code> and <code>margin-top</code> it is working only for one resolution.</p>