submission by jtoy
drops = []
function setup(){
  var myCanvas = createCanvas(windowWidth,windowHeight); //you must keep this line unmodified
  frameRate(5)
  for(i=0;i<20;i++){
    drops.push({x:random(width),y:random(height),step:1})
  }
}
function draw() {
  //start writing your code here
  background(25,0,250)
 fill(50,50,255)
 //noStroke()
  for(i=0;i<drops.length;i++){
    d = drops[i]
     for(ii=d['step'];ii>0;ii--){
      ellipse(d['x'],d['y'],ii*15,ii*15)
    }
     d['step'] += d['step']
     if(d['step'] > 20 && random(2) > 0.5){
        d['x'] = random(width)
       d['y'] = random(height)
        d['step'] = random(1,3)
     }
  }

}