#board {
  margin: auto;
  padding-top: 4vw;
  width: 50vw;
  height: 50vh;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: auto;
}
.box::before {
  content: "";
  display: block;
  padding-top: 100%;
}

body {
  padding: 0;
  margin: 0;
  background-color: #212121;
}
body .grid {
  max-width: 570px;
  margin: 30px auto;
  box-sizing: border-box;
  border: 10px solid #2a351f;
}