basic

function setup() {

  width=500;

  height=500

  createCanvas(width, height);

  background(0);

  noStroke();

  rectMode(CENTER);

  for(let i=0; i<250; i++){

    let x = random(width/2);

    let y = random(height);

    let diameter = random(y/15.0);

    fill(random(230,255),random(0,20),random(0,20),127);

    ellipse(x,y,diameter,diameter);

  }

  for(let i=0; i<250; i++){

    let x = random(height);

    let y = random(width/2);

    let diameter = random((width-x)/15.0);

    fill(random(0,15),random(180,200),random(200,255),127);

    rect(x,y,diameter,diameter);

  }

  for(let i=0; i<250; i++){

    let x = random(width/2)+width/2;

    let y = random(height);

    let diameter = random((height-y)/15.0);

    fill(random(0,15),random(230,255),random(100,127),127);

    ellipse(x,y,diameter,diameter);

  }

  for(let i=0; i<250; i++){

    let x = random(height);

    let y = random(width/2)+width/2;

    let diameter = random(x/15.0);

    fill(random(220,255),random(220,255),random(0,20),127);

    rect(x,y,diameter,diameter);

  }

}

​