style.css

:root {
  --cube-size: min(30vw, 30vh);
  --cube-half-size: calc(var(--cube-size) / 2);
  --ff-size: calc(0.9 * var(--cube-size));
  --cube-face-color: linear-gradient(rgba(212, 0, 0, 0.1), rgb(56, 0, 238));
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 99%;
  font-family: monospace;
}

body {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-around;
  align-items: center;
  padding-bottom: 5rem;
  padding-inline: 5rem;
}

.github-link {
  display: flex;
  color: black;
  text-decoration: none;
  align-items: center;
}

.github-link:hover {
  text-decoration: underline;
}

.github-link:visited {
  color: black;
}

.github-link img {
  width: 1.3em;
  height: 1.3em;
  margin-right: 0.7em;
}

.rotation-container {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  height: calc(var(--cube-size) * 1.5);
  width: calc(var(--cube-size) * 1.5);
  /* border: 1px solid red; */
  perspective: calc(var(--cube-size) * 1.5);
}

.cube {
  /* border: 1px solid red; */
  width: var(--cube-size);
  height: var(--cube-size);
  transform-style: preserve-3d;
  -moz-transform-style: preserve-3d;
  -webkit-transform-style: preserve-3d;
}

.face {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: var(--ff-size);
  width: 100%;
  height: 100%;
  border: 1px solid gray;
}

.cube__face {
  position: absolute;
  background: var(--cube-face-color);
}

.cube__face-front {
  background: var(--cube-face-color);
  transform: translateZ(var(--cube-half-size));
}

.cube__face-back {
  background: var(--cube-face-color);
  transform: rotateY(180deg) translateZ(var(--cube-half-size));
}

.cube__face-right {
  transform: rotateY(90deg) translateZ(var(--cube-half-size));
}

.cube__face-left {
  transform: rotateY(-90deg) translateZ(var(--cube-half-size));
}

.cube__face-top {
  transform: rotateX(90deg) translateZ(var(--cube-half-size));
}

.cube__face-bottom {
  transform: rotateX(-90deg) translateZ(var(--cube-half-size));
}

.backface-hidden {
  backface-visibility: hidden;
  -moz-backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

.face--select-disabled {
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
}

.transition-transform {
  transition: transform 0.3s ease;
}