createCanvas(1000, 1000);

}

​

// version 3

const array = [];

const array2 = [];

var lastP = {

  x : -1,

  y : -1

};

var lastP2 = {

  x : -1,

  y : -1

};

​

function draw() {

  background(255, 200, 200);

  var p = {

    x : mouseX,

    y : mouseY

  };

  var dx = (p.x - lastP.x);

  var dy = (p.y - lastP.y);

  var lineLen = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));

  var ratio = 50/lineLen;

  var newDx = dy*ratio;

  var newDy = -dx*ratio;

  var p2 = {

    x : p.x + newDx,

    y : p.y + newDy

  }

​

  if (lastP != p) {

    array.push(p);

    array2.push(p2);

  }

  lastP = p;

  lastP2 = p2;

  if (array.length > 100) {

    array.shift();

    array2.shift();

  }

  for (var i = 0; i < array.length - 1; i++) {

    line(array[i].x, array[i].y, array[i+1].x, array[i+1].y);

    line(array2[i].x, array2[i].y, array2[i+1].x, array2[i+1].y);

  }

}