SOURCE

function setup(){
    createCanvas(400,400);
    background(255);
}
function draw(){
    for(let x=5; x<= height; x+=50){
        for(let y=5; y<=width; y+=50){
             fill(255,80,80);
         rect(x,y,50,50);
    }
  }
     for(let x=10; x<= height; x+=50){
        for(let y=10; y<=width; y+=50){
         rect(x,y,40,40);
        }
     }
    for(let x=15; x<= height; x+=50){
        for(let y=15; y<=width; y+=50){
             rect(x,y,30,30);
   }
    }
    for(let x=20; x<= height; x+=50){
        for(let y=20; y<=width; y+=50){
         rect(x,y,20,20);
  }
    }
    for(let x=25; x<= height; x+=50){
        for(let y=25; y<=width; y+=50){
         rect(x,y,10,10);
  }
    }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.1.9/p5.min.js"></script>