let lineWidth;

​

function setup() {

  createCanvas(400, 300);

  background(0);

}

​

function draw() {

  squareSize = random(50, 250);

  lineWidth = random(4, 28);

  rectMode(CENTER);

  strokeWeight(lineWidth);

  stroke(0, 0, 255, 20);

  fill(0, 255, 0, 10);

  square(200, 150, squareSize);

}

​