hourglass

int num = 20;
float offset, step;
Linn[] lines = new Linn[num-2];
color bg = #35263D;
color q = #ABB785;

void setup() {
  size(500, 500);
  background(bg);

  float y = 50;
  float theta = 0;
  step = (height-2*y)/num;
  println(step);

  for (int i=0; i<num-2; i++) {
    lines[i]= new Linn(int(y+step), theta);
    y += step;
    theta += TAU/num ;
  }
}

void draw() {
  background(bg);

  for (int i=0; i<lines.length; i++) {
    lines[i].display();
  }

  if (frameCount % 1 == 0 && frameCount<121) saveFrame("image-####.gif");

}


class Linn {
  float offset, theta, y;

  Linn(float _y, float _theta) {
    y = _y;
    theta = _theta;
  }

  void display() {
    offset = map(sin(theta), -1, 1, 30, width/3);
    fill(q);
    stroke(q);
    strokeWeight(2);
    quad(width/2, y, width/2+offset, y, width/2, y+step, 50+(width/2-50)-offset, y+step);
    theta += 0.0523;
  }
}