oscillation.js

var r = new Rune({
  container: "#canvas",
  width: 800,
  height: 600
});

var rad;
var offset;
var angle;
var k;

r.rect(0, 0, r.width, r.height).fill(0);

rad = 100;
offset = r.height /2;
angle = 0;

var myShape = r.polygon(0, 0)
  .fill(false)
  .stroke(255)

while(angle < 100) {

  angle += 0.09;
  rad += 0.05;
  k = 4/5;

  var x = Math.cos(k * angle) * Math.cos(angle) * rad;
  var y = Math.cos(k * angle) * Math.sin(angle) * rad;

  myShape.lineTo(x + r.width / 2, y + r.height / 2, 10, 10)
}

r.draw();