var y;

​

function setup() {

  createCanvas(200, 200);

  x = width / 2;

  y = width / 2;

  background(32);

  stroke(255);

}

​

function draw() {

​

  var randomValue = random();

  if(randomValue < .25){

    x--;

  }

  else if(randomValue < .5){

    x++;

  }

  else if(randomValue < .75){

    y--;

  }

  else{

    y++;

  }

  if(x < 0){

    x = width;

  }

  else if(x > width){

    x = 0;

  }

  if(y < 0){

    y = height;

  }

  else if(y > height){

    y = 0;

  }

  point(x, y);

}

​