Make div 'fullscreen' onClick of a button?

Here's a tweaked version of my answer from yesterday:

DEMO

$(':button').click(function() {
  $('div > div').css({
      position:'absolute', //or fixed depending on needs
      top: $(window).scrollTop(), // top pos based on scoll pos
      left: 0,
      height: '100%',
      width: '100%'
  });
});