<section>
  <div class="box aspect-ratio" style='--aspect-ratio: 9/16'>
    <span><strong>9:16</strong><br>(177.77%)</span>
  </div>
  <div class="box aspect-ratio" style='--aspect-ratio: 3/4'>
    <span><strong>3:4</strong><br>(133.33%)</span>
  </div>
  <div class="box aspect-ratio" style='--aspect-ratio: 1/1'>
    <span><strong>1:1</strong><br>(100%)</span>
  </div>
  <div class="box aspect-ratio" style='--aspect-ratio: 4/3'>
    <span><strong>4:3</strong><br>(100%)</span>
  </div>
  <div class="box aspect-ratio" style='--aspect-ratio: 16/9'>
    <span><strong>16:9</strong><br>(56.25%)</span>
  </div>
</section>

/* Aspect Ratio */
.aspect-ratio {
  height: auto;
  position: relative;
}

.aspect-ratio::before {
  content: "";
  display: block;
  padding-top: calc(100% / (var(--aspect-ratio)));
}

.aspect-ratio > :first-child {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

/* Style */
:root {
  --green-lightest: #6bc85b;
  --green-light: #449720;
  --green: #2B6D10;
  --green-dark: #163908;
  --green-darkest: #0C2004
}

body {
  min-height: 100vh;
  background: #D4D4D4;
  margin: 0;
}

section {
  padding: 2rem;
  min-height: 100vh;
  max-width: 80ch;
  margin: auto;
  display: grid; 
  gap: 1rem;
  justify-content: center;
  grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
  grid-template-rows: auto;
  align-items: center;
  justify-items: center;
}

.box {
  flex: 1;
  max-width: 100%;
  width: 100%;
  border: 1px solid #878787;
  border-radius: 4px;
  background-color: #878787;
  box-shadow: 0 0 4px rgba(0,0,0,.16), 0 4px 8px rgba(0,0,0,.29);
}

span {
  display: grid;
  place-items: center; 
  place-content: center; 
  font-family: monospace; 
  color: #fff;
  text-align: center;
  font-size: 1.2rem;
  line-height: 1.2;
}

.box:nth-child(1) {
  border-color: var(--green-lightest);
  background-color: var(--green-lightest);
}

.box:nth-child(2) {
  border-color: var(--green-light);
  background-color: var(--green-light);
}

.box:nth-child(3) {
  border-color: var(--green);
  background-color: var(--green);
}

.box:nth-child(4) {
  border-color: var(--green-dark);
  background-color: var(--green-dark);
}

.box:nth-child(5) {
  border-color: var(--green-darkest);
  background-color: var(--green-darkest);
}