title: question how to increase game speed
body: <p>i'm building a simple flash game that shows up little spheres (different in size, x and y). Users has to click on them to remove them.
  the more seconds pass by, the faster the spheres have to show up. 
  if you have to many spheres on the screen, you lose. So if you are a very fast and accurate clicker, you get much further then if you are slow. 
  my question now is: how can I manage the speed of the spheres showing up?
  I'm using a timer now, that times every 2 seconds. So in the beginning we need to go slow, the more seconds have passed the more spheres show up. Or the more spheres you've clicked away, the faster the games goes.</p>
  
  <p>any ideas?</p>
  
  <p>thanks!</p>