title: Inverted border-radius?
body: <p>Given this simple plunkr : <a href="http://plnkr.co/edit/aTM80EUHAYds1h5TIXTh?p=preview" rel="nofollow">http://plnkr.co/edit/aTM80EUHAYds1h5TIXTh?p=preview</a></p>
  
  <p>I would like to be able to be able to have a <code>border-radius</code> on the inner corner between the two divs (the only sharp corner on this example). I added a <code>div#corner</code> (currently on <code>display:none</code>) that could do the trick, but I have really no idea how (and if it's even possible) to have an inverted <code>border-radius</code>.</p>
  
  <p>How could I get that effect without using an image?</p>
  
  <p><strong>edit</strong></p>
  
  <p><a href="http://plnkr.co/edit/9Hc9nr?p=preview" rel="nofollow">Here is</a> a better, more flexible way of doing it, thanks to @Colandus for the help.</p>