// Simple animation test.

// Start out with an undefined window.  This will get defined the first
// time we call graphics.show[].
win = undef

while (true)
{
   for x = 0 to 10 step .01
   {
      // Create a new graphics object for each frame.
      g = new graphics

      // Draw 3 circles
      g.color[1,0,0, .8]
      g.fillEllipseCenter[sin[x],cos[x],1,1]

      g.color[1,1,0,.7]
      g.fillEllipseCenter[x,sin[x],.9,.9]

      g.color[0,0,1,.5]
      g.fillEllipseCenter[x/2,0,1.1,1.1]

      // If this is the first frame, show it and save the window.
      if (win == undef)
         win = g.show[]
      else
         win.replaceGraphics[g] // Not first frame, replace graphics.

      sleep[1/30 s]
   }

   // Pause before restarting animation.
   sleep[2 s]
}