//by default p5.js always makes a canvas for you, even if you forget to type this function

  createCanvas(500, 400);

}

​

function draw() {

  background(0,0,255);

  //instruction(arguments);

  //noFill();

  stroke(100);

  //reference point for the rect becomes the center

  rectMode(CENTER);

  rect(width/2,height/2,30,40,20);

}