let amplitude = 20;

let yoff = 0;

​

function setup() {

  createCanvas(800, 800);

  background(20);

  angleMode(DEGREES);

}

​

function draw() {

  let yADJ = map(mouseY, 0, height, -500, 500)

  yoff = (yoff + yADJ)%height;

  a = (a+10)%width;

  push();

  translate(a,amplitude*sin(a)+yoff);

  ellipse(0,0,cos(a+frameCount)*50);

  pop();

}