​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  for (let i = 0; i < mousePositions.length - 1; i++) {

    let x = mousePositions[i].x;

    let y = mousePositions[i].y;

    let xNext = mousePositions[i + 1].x;

    let yNext = mousePositions[i + 1].y;

    line(x, y, xNext, yNext);

  }

  mousePositions.push({x: mouseX, y: mouseY});

  if (mousePositions.length > 100) {

    mousePositions.shift(); 

  }

}