let g;

let b;

let a;

​

​

function setup() { 

  createCanvas(400, 400);

  rectMode(CENTER);

} 

​

function draw() { 

  background(220);

  r = random(255); // r is a random number between 0 - 255

  g = random(100,200); // g is a random number betwen 100 - 200

  b = random(100); // b is a random number between 0 - 100

  a = random(200,255); // a is a random number between 200 - 255

  noStroke();

  fill(r, g, b, a);

  rect(200,200,100,100);

}