title: iPhone "slide to unlock" animation
body: <p>Any ideas as to how Apple implemented the "slide to unlock" (also, "slide to power off" is another identical example) animation?</p>
  
  <p>I thought about some sort of animating mask - but masking is not available on the iPhone OS for performance reasons.</p>
  
  <p>Is there some private API effect (like SuckEffect) that they might have used? A spotlight type of effect?  Some Core Animation thing?</p>
  
  <p>Edit:
  It's definitely not a series of stills.  I've seen examples of being edit a plist value or something and customize the string on jailbroken iphones.</p>