createCanvas(400, 400);

}

​

function draw() {

  background(200);

​

  var period = 1000.0; // milliseconds

  var angle = TWO_PI * millis()/period;

  var center = width/2;

  var amplitude = 100; 

  var frequency = 1.0;

  var phase = 0; 

  var px = center + amplitude * sin(phase + frequency * angle); 

  ellipse(px, 200, 40, 40);

}