title: Catching multiple keystrokes simultaneously in Cocoa
body: <p>I have used 4 <code>NSButton</code>s and assigned them to the 4 arrow keys separately to move in four different directions. Now I want to use two keystrokes, left arrow and up arrow together simultaneously, for north east movement, how can I do it?</p>
  
  <p>I am only able to use one keystroke at a time , I need to catch two key strokes simultaneously, I need it for my game project.</p>