style.css

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  overflow: hidden;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

.view {
  overflow: hidden;
  background-color: #808080;
  touch-action: none;
  user-select: none;
  width: 100vw;
  height: 100vh;
}

.world {
  position: absolute;
  left: 50%;
  top: 50%;
  transform-origin: 0 0;
  translate: 0 0;
  scale: 1;
}

.world.animate {
  transition: scale 200ms;
}

.cube {
  --x: 0;
  --y: 0;
  --z: 0;
  position: absolute;
  width: 100px;
  height: 100px;
  background-color: #f00;
  background-image: conic-gradient(
    from -1.0636978224025597rad at center,
    #fff4 0deg 2.1273956448051194rad,
    #0004 2.1273956448051194rad 4.205290475992353rad,
    #0000 4.205290475992353rad 360deg
  );
  left: calc((var(--x) - var(--z)) * 45px);
  top: calc((var(--x) + var(--z)) * 25px - var(--y) * 50px);
  margin-left: -50px;
  margin-top: -50px;
  z-index: calc(var(--x) + var(--y) + var(--z));
  clip-path: polygon(50% 0%, 95% 25%, 95% 75%, 50% 100%, 5% 75%, 5% 25%);
  transition: filter 200ms, scale 100ms, left 200ms ease-in-out, top 200ms ease-in-out, z-index 200ms;
}

.cube:hover {
  filter: brightness(0.75);
  scale: 1.1;
}

.cube:active {
  filter: brightness(0.5);
  scale: 0.9;
}

.cube.placing {
  animation: cube-place 100ms ease-in-out;
}

.cube.breaking {
  animation: cube-break 150ms ease-out forwards;
  pointer-events: none;
}

.world.rot-0 .cube {
  left: calc((var(--x) - var(--z)) * 45px);
  top: calc((var(--x) + var(--z)) * 25px - var(--y) * 50px);
  z-index: calc(var(--x) + var(--y) + var(--z));
}

.world.rot-90 .cube {
  left: calc((var(--z) * -1 - var(--x)) * 45px);
  top: calc((var(--z) * -1 + var(--x)) * 25px - var(--y) * 50px);
  z-index: calc(var(--x) + var(--y) + var(--z) * -1);
}

.world.rot-180 .cube {
  left: calc((var(--x) * -1 - var(--z) * -1) * 45px);
  top: calc((var(--x) * -1 + var(--z) * -1) * 25px - var(--y) * 50px);
  z-index: calc(var(--x) * -1 + var(--y) + var(--z) * -1);
}

.world.rot-270 .cube {
  left: calc((var(--z) - var(--x) * -1) * 45px);
  top: calc((var(--z) + var(--x) * -1) * 25px - var(--y) * 50px);
  z-index: calc(var(--x) * -1 + var(--y) + var(--z));
}

@keyframes cube-place {
  from {
    scale: 0;
    opacity: 0;
  }
}

@keyframes cube-break {
  to {
    scale: 1.5;
    opacity: 0;
  }
}

.hud {
  position: fixed;
  padding: 1em;
  width: 100%;
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;
  justify-content: space-between;
  align-items: center;
  align-content: flex-start;
}

.rotator-wrapper {
  display: flex;
  flex-direction: row;
  flex-wrap: nowrap;
  align-items: center;
  justify-content: center;
}

button {
  font-size: 1em;
}

.author {
  position: fixed;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  text-align: center;
  width: fit-content;
  font-size: 16pt;
  color: white;
}

.btn-help {
  position: fixed;
  bottom: 1em;
  left: 1em;
  font-size: 16pt;
}

dialog {
  text-align: center;
  border: none;
  outline: none;
  background-color: white;
  box-shadow: 0 0 14px #0004;
  padding-top: 0;
  padding-bottom: 0;
  overflow: visible;
  width: 512px;
}

dialog::before,
dialog::after {
  content: "";
  position: absolute;
  transform: translate(-50%);
  border-left: 256px solid transparent;
  border-right: 256px solid transparent;
  box-sizing: content-box;
}

dialog::before {
  bottom: 100%;
  border-bottom: 64px solid white;
}

dialog::after {
  top: 100%;
  border-top: 64px solid white;
}

.btn-close {
  appearance: none;
  background-color: #888;
  color: white;
  position: absolute;
  transform: translate(-50%, -50%);
  left: 50%;
  width: 32pt;
  height: 32pt;
  font-size: 24pt;
  font-family: monospace;
  border: none;
  outline: none;
  margin-top: -32px;
  clip-path: polygon(50% 0%, 95% 25%, 95% 75%, 50% 100%, 5% 75%, 5% 25%);
  transition: background-color 100ms;
}

.btn-close::before {
  content: var(--icon, "?");
}

.btn-close:is(:hover, :focus-visible) {
  background-color: #f00;
}

.btn-close:is(:hover, :focus-visible):before {
  content: "X";
}

.btn-close:active {
  background-color: #800;
}

.content {
  text-align: left;
  max-height: 512px;
  overflow: auto;
  scrollbar-width: thin;
  animation: open 250ms ease-in-out;
}

@keyframes open {
  from {
    max-height: 0;
  }
}

@keyframes close {
  to {
    max-height: 0;
  }
}