Audiovisuals with SC - Example03a - louder is brighter

See /f0blog/audiovisuals-with-sc/

//Example03a - louder is brighter
(
s.latency= 0.05;
s.waitForBoot{

  //--window setup
  var width= 640, height= 480;
  var w= Window("Example03a - louder is brighter", Rect(99, 99, width, height), false);
  var u= UserView(w, Rect(0, 0, width, height));

  //--variables
  var pat= Pn(Pshuf(#[0, 0, 0, 0, 0.1, 0.25, 0.5, 0.75, 1, 1], 8), inf).asStream;
  var syn= SynthDef(\av, {|amp= 0|
    var z= LPF.ar(LFSaw.ar(#[300, 301, 80, 81], 0, amp).mean, 2000);
    Out.ar(0, Pan2.ar(z));
  }, #[0.05]).play(s);  //short lag time to avoid clipping
  var amp= 0;

  //--interface
  ~radius= 100;
  ~fps= 10;

  //--main loop
  u.drawFunc= {
    amp= pat.next;  //get the next value from the stream
    syn.set(\amp, amp);  //send to the synth
    Pen.translate(width*0.5, height*0.5);  //offset drawing to the centre
    Pen.fillColor= Color.grey(amp);  //fill with color corresponding to amp
    Pen.fillOval(Rect.aboutPoint(Point(0, 0), ~radius, ~radius));
  };

  //--window management
  u.clearOnRefresh= true;
  u.background= Color.grey(0.5);  //keep neutral background
  w.onClose= {syn.free};
  w.front;
  CmdPeriod.doOnce({w.close});
  Routine({
    var nextTime;
    while({w.isClosed.not}, {
      nextTime= Main.elapsedTime+(1/~fps);
      u.refresh;
      (nextTime-Main.elapsedTime).max(0.001).wait;
    });
  }).play(AppClock);
};
)

//change these while the program is running
~radius= 200;
~radius= 300;
~fps= 30;
~fps= 15;
~fps= 5;
~radius= 15;

//close the window to stop or press cmd+.