let x = [];

let y = [];

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  noStroke();

  noCursor();

  for(i = 0; i < num; i++){

    x[i] = 0;

    y[i] = 0;

  }

}

​

function draw() {

  background(0);

  //Copy array values from back to front

  for(i = num-1; i > 0; i--){

    x[i] = x[i - 1];

    y[i] = y[i - 1];  

  }

  x[0] = mouseX; //set the first element

  y[0] = mouseY;

  for(i = 0; i < num; i++){

    fill(i * 4);

    circle(x[i], y[i], 240);

  }

}