Pulsing lines

color black = #000000;
color white = #f1f1f1;

void setup() {
  size(800, 600, P2D);
  rectMode(CORNER);
  noStroke();
  fill(black);
}

void draw() {  
  background(white);

  for (int i = 0; i < 35; i++) {

    float wave = map(sin(radians(frameCount * i)), -1, 1, 0, 20);

    pushMatrix();
    rect(50 + i*20, 50, wave, 500);
    popMatrix();
  }
}