final int SIZE = 120;

float angle = 0;
float maxAngle = 0.2;
float dAngle = 0.001;

void setup() {
  size(600, 600);
  rectMode(CENTER);
  stroke(0);
  strokeWeight(2);
  noFill();
}

void draw() {
  background(255);
  int dir = 1;
  for (int y = SIZE / 2; y < height; y += SIZE) {
    for (float x = SIZE / 2; x < width; x += SIZE) {
      drawSquare(x, y, SIZE, angle, dir);
      dir = -dir;
    }
  }
  angle += dAngle;
  if (angle > maxAngle || angle < 0) {
    dAngle = -dAngle;
  }
}

void drawSquare(float xc, float yc, float size, float angle, int dir) {
  pushMatrix();
  translate(xc, yc);
  float coef = 1 / (sin(angle) + cos(angle));
  for (int i = 0; i < 20; i++) {
    rect(0, 0, size, size);
    size *= coef;
    rotate(dir * angle);
  }
  popMatrix();
}