title: iOS: How do I create irregularly shaped / partially transparent & click-thru buttons
body: <p>How would I create these buttons, so that clicking handles correctly?</p>
  
  <p><img src="https://i.stack.imgur.com/CYEhJ.png" alt="alt text"></p>
  
  <p>Each button is a <code>.png</code>,  transparent outside of the coloured square.  I need a transparent areas to be click-thru.</p>