<div class="board">
  <div class="board__item">
    <div class="panel panel--16x9">
      <div class="panel__content">16:9</div>
    </div>
  </div>
  <div class="board__item">
    <div class="panel panel--4x3">
      <div class="panel__content">4:3</div>
    </div>
  </div>
  <div class="board__item">
    <div class="panel panel--1x1">
      <div class="panel__content">1:1</div>
    </div>
  </div>
</div>

/* Global */

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: Arial, Gerogia, sans-serif;
  font-size: 2rem;
  font-weight: bold;
  color: #fff;
}

/* Board */

.board {
  width: 100%;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  display: flex;
  align-items: center;
  justify-content: space-around;
  padding: 15px;
}

.board__item {
  width: 500px;
  margin: 0 15px;
  border: 1px solid #fff;
  background-image: linear-gradient(to right bottom, rgba(255,10,22,1), #ffffff);
  text-shadow: 3px 2px 0px rgba(255,10,22,1);
  box-shadow: 2px 2px 3px 0px rgba(255,10,22,0.5);
}

/* Panel */

.panel {
  position: relative;
  width: 100%;
}

.panel--16x9 {
  padding-top: calc((9 / 16) * 100%);
}

.panel--4x3 {
  padding-top: calc((3 / 4) * 100%);
}

.panel--1x1 {
  padding-top: 100%;
}

.panel__content {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}