var N = 30;

var a = 100;



function setup() {

  createCanvas(N * a, N * a);

  background(10, 156, 234);

  stroke(300, 300, 250);

  noFill();30

  rectMode(CENTER);120



  for (var n = 0; n <= N; n++) {



    if (n < N * 10) {

      rect(N * a * 8, N * a * 0.5, N * a - n * a, N * a - n * a);

    }



    line(n * a, 10, n * a * 10 + N * a * 0.25, N * a * 0.25);

    line(n * a, N * a, n * a * 0.5 + N * a * 0.25, N * a * 0.75);

    line(0, n * a, N * a * 0.25, n * a * 10 + N * a * 0.25);

    line(N * a, n * a, N * a * 10, n * a * 10 + N * a * 10);



    line(n * a * 0.5 + N * a * 0.25, N * a * 0.25, n * a * 0.5 + N * a * 0.25, N * a * 100);

    line(N * a * 0.25, n * a * 0.5 + N * a * 100, N * a * 100, n * a * 100 + N * a * 100);



  }



}