* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  display: grid;
  place-content: center;
  grid-template-areas: "body";
  overflow: hidden;
}

body::before,
body::after {
  --size: 150vmax;
  --duration: 8s;
  
  content: "";
  grid-area: body;
  width: var(--size);
  height: var(--size);
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

body::before {
  animation-name: rotate;
  animation-duration: var(--duration);
  background: linear-gradient(to left, var(--palette));
}

body::after {
  animation-name: rotate, fade;
  animation-duration: calc(var(--duration) / 2), var(--duration);
  background: linear-gradient(to right, var(--palette));
}

@keyframes rotate {
  to {
    transform: rotate(1turn);
  }
}

@keyframes fade {
  50% {
    opacity: 0;
  }
}

/* Gradients generated at https://learnui.design/tools/gradient-generator.html */
body {
  --rotate: 0deg;
  --palette: #1f005c, #5b0060, #870160, #ac255e, #ca485c, #e16b5c, #f39060,
    #ffb56b;
}

[data-color="1"] {
  --rotate: 90deg;
  --palette: #004466, #006080, #007e90, #009b97, #29b794, #74d18b, #b7e881,
    #fffb80;
}

[data-color="2"] {
  --rotate: 180deg;
  --palette: #f3ff17, #ffde00, #ffb900, #ff8f39, #ff6062, #ff298b, #ff00b5, #ff1fdd;
}

[data-color="3"] {
  --rotate: 270deg;
  --palette: #054ce6, #0072ff, #008fff, #00a5ff, #00b8e4, #00c9bb, #00d890, #36e367;
}

/* Controls */
.controls {
  --offset: 0.5rem;
  position: fixed;
  top: var(--offset);
  left: var(--offset);
  right: var(--offset);
  width: calc(100% - var(--offset) * 2);
  display: flex;
  justify-content: space-between;
  padding-left: min(5vmin, env(safe-area-inset-left));
  padding-right: min(5vmin, env(safe-area-inset-right));
  z-index: 1;
}

button {
  display: flex;
  align-items: center;
  font-family: system-ui;
  font-size: inherit;
  padding: 1rem;
  color: white;
  fill: currentcolor;
  background-color: transparent;
  border: none;
  cursor: pointer;
  touch-action: manipulation;
}

button:active {
  transform: translateY(1px);
}

.btn-colors [data-icon] {
  width: 1.4em;
  transform: rotate(var(--rotate));
}

.btn-fullscreen [data-icon] {
  width: 1.2em;
}

[data-icon="close"] {
  display: none;
}

.is-fullscreen [data-icon="open"] {
  display: none;
}

.is-fullscreen [data-icon="close"] {
  display: block;
}