var py = 0;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(200);

​

  var A = 0.965;

  var B = 1.0 - A; 

  var targetX = mouseX; 

  var targetY = mouseY; 

  px = A*px + B*targetX;

  py = A*py + B*targetY;

  ellipse(px, py, 40, 40);

}