function setup() {

  createCanvas(500, 500);

  snake = new Snake(250, 250);

  snake.add();

  snake.add();

  snake.add();

  console.log(snake.circles);

}

​

function keyPressed(){

  snake.xchange = 0; snake.ychange = 0;

  if (keyCode === LEFT_ARROW) snake.xchange = -1;

  if (keyCode === RIGHT_ARROW) snake.xchange = 1;

  if (keyCode === UP_ARROW) snake.ychange = -1;

  if (keyCode === DOWN_ARROW) snake.ychange = 1;

}

​

function draw() {

  background(220);

  snake.move();

  snake.draw();

}

​

class Snake{

  constructor(x, y){

    this.r = 10;

    this.circles = [new Circle(x, y)];

    this.xchange = -1;

    this.ychange = 0;

  }

  draw(){

    noStroke();

    fill(255, 0, 0);

    for (let i=0; i<this.circles.length; i++)

      this.circles[i].draw(this.r);

  }

  add(){

    if (this.xchange === -1){ 

      let temp = new Circle(this.circles[this.circles.length-1].x+2*this.r, this.circles[this.circles.length-1].y);

      this.circles.push(temp);

    }

  }

  move(){

    for (let i=this.circles.length-1; i>0; i--){

      if (this.xchange !== 0){

        if (this.circles[i].y === this.circles[0].y)

          this.circles[i].x += this.xchange;

        else{

          if (this.circles[0].y - this.circles[i].y > 0) this.circles[i].y += 1;

          else this.circles[i].y -= 1;

        }

      }

      else{

        if (this.circles[i].x === this.circles[0].x)

          this.circles[i].y += this.ychange;

        else

          if (this.circles[0].x - this.circles[i].x > 0) this.circles[i].x += 1;

          else this.circles[i].x -= 1;  

      }

    }

    this.circles[0].x += this.xchange;

    this.circles[0].y += this.ychange;

    if (this.circles[0].x < -this.r) this.circles[0].x = width+this.r;

    else if (this.circles[0].x > (width+this.r)) this.circles[0].x = -this.r;

    else if (this.circles[0].y < -this.r) this.circles[0].y = height+this.r;

    else if (this.circles[0].y > (height+this.r)) this.circles[0].y = -this.r;

  }

}

​

class Circle{

  constructor(x, y){

    this.x = x;

    this.y = y;

  }

  draw(r){

    circle(this.x, this.y, 2*r);

  }

}