styles.css

body {
  margin-top: 70px;
  width: calc(100vw/2);
  height: calc(100vw/2);
  border: solid 5px #222;
  position: center;
  vertical-align: center;
  background-color: black;
  text-align: center;
  font-family: 'Readex Pro', sans-serif;
  max-width: 640px;
  max-height: 640px;
}

div {
  display: flex;
  justify-content: center;
  align-items: center;
  color: #666666;
  box-sizing: border-box;
  float: left;
  width: calc(100vw/16);
  height: calc((100vw)/16);
  padding: 0;
  max-width: 80px;
  max-height: 80px;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

html {
  margin: auto;
  display: table;
  color: white;
  background-color: black;
}

.chessboard {
  font-size: min(calc(100vw/6), 10px);
  color: black;
}

#result {
  font-family: 'Times', serif;
  margin: 0;
  position: absolute;
  top: 10px;
  left: 50%;
  transform: translate(-50%);
}

#reset {
  position: absolute;
  left: calc(100vw/2 - 25px);
  top: calc(100vw/2 + 95px);
  top: min(calc(100vw/2 + 105px), 745px);
}

img {
  width: calc(100vw/16);
  user-drag: none;
  user-select: none;
  -webkit-user-drag: none;
  -webkit-user-select: none;
  -ms-user-select: none;
}