.content
  - for(i=0; i<2; i++)
    .bars
      - for(b=0; b<7; b++)
        .bar

:root {
  --b: #262626;
  --w: #dcdcd2;
  --s: 2s; /* change speed */
} 

*, *:before, *:after {
  box-sizing: border-box;
  transform-style: preserve-3d;
}

body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--b);
}

.content {
  width: 50vmin;
  height: 50vmin;
  text-align: center;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  perspective: 1000vmin;
}

.bars {
  width: 100%;
  height: 100%;
  position: absolute;
  padding: 6.5vmin 3vmin;
  animation: mirror1 calc(var(--s) * 2) ease 0s infinite ;
}

.bars + .bars {
  transform: rotate(90deg) rotateX(180deg);
  animation: mirror2 calc(var(--s) * 2) ease calc(var(--s) / 2) infinite;
}

.bar {
  width: 44vmin;
  height: 3vmin;
  margin: 2vmin 0vmin;
  background: linear-gradient(90deg, #fff0 33%, var(--w) 33% 67%, #fff0 67% 100%);
  animation: grow var(--s) ease-in-out 0s infinite alternate; 
  background-size: 300%;
  background-position-x: -203%;
}

@keyframes mirror1 {
  0%, 47%, 99.99%, 100% { transform: rotate(180deg) rotateX(0deg); }
  47.01%, 99.98% { transform: rotate(180deg) rotateX(180deg); }
}

@keyframes mirror2 {
  0%, 47%, 99.99%, 100% { transform: rotate(90deg) rotateX(180deg); }
  47.01%, 99.98% { transform: rotate(90deg) rotateX(0deg); }
}

@keyframes grow {
  0%, 25% { background-position-x: -297%; }
  45%, 55% { background-position-x: -250%; }
  75%, 100% { background-position-x: -203%; }
}

.bar:nth-child(2) {
  animation-delay: calc(var(--s) * -0.02);
}
.bar:nth-child(3) {
  animation-delay: calc(var(--s) * -0.04);
}
.bar:nth-child(4) {
  animation-delay: calc(var(--s) * -0.06);
}
.bar:nth-child(5) {
  animation-delay: calc(var(--s) * -0.08);
}
.bar:nth-child(6) {
  animation-delay: calc(var(--s) * -0.1);
}
.bar:nth-child(7) {
  animation-delay: calc(var(--s) * -0.12);
}

.bars:nth-child(2) .bar:nth-child(1) {
  animation-delay: calc(calc(var(--s) * -0.001) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(2) {
  animation-delay: calc(calc(var(--s) * -0.02) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(3) {
  animation-delay: calc(calc(var(--s) * -0.04) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(4) {
  animation-delay: calc(calc(var(--s) * -0.06) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(5) {
  animation-delay: calc(calc(var(--s) * -0.08) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(6) {
  animation-delay: calc(calc(var(--s) * -0.1) - calc(var(--s) / 2));
}
.bars:nth-child(2) .bar:nth-child(7) {
  animation-delay: calc(calc(var(--s) * -0.12) - calc(var(--s) / 2));
}

// Insipred by this image from Pinterest:
// https://www.pinterest.com/pin/14425661292261254/