App.css

:root {
  --square-size-units: 3.5;
  --square-size: calc(var(--square-size-units) * 1vh);
  --board-size: 8;
}

.app {
  height: 100vh;
  width: 100vw;
  overflow: hidden;
}

.app-wrapper {
  height: 100vh;
  width: 100vw;
  max-width: 600px;
  margin: auto;
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 16px 0;
  justify-items: center;
}

.undo {
  grid-column-start: 1;
  grid-column-end: 3;
}

.header {
  text-align: center;
  margin: 0;
}

.options {
  display: grid;
  place-items: center;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 1fr 1fr;
  gap: 8px;
}

.game {
  width: 100%;
  display: grid;
  grid-template-rows: 1fr 1fr;
  touch-action: none;
  place-items: center;
  align-items: stretch;
  gap: 2vh 0;
}

.board-wrapper {
  display: grid;
  place-items: center;
  width: 100%;
}

.board {
  aspect-ratio: 1;
  height: 100%;
  width: auto;
  height: calc(8 * var(--square-size));
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);

  outline: 2px grey solid;
  touch-action: none;
}

@keyframes blink {
  0% {
    opacity: 1;
  }
  50% {
    opacity: 0.25;
  }
  100% {
    opacity: 1;
  }
}

.board .square {
  outline: 1px grey solid;
}

.square.transition {
  transition: all 200ms;
}

.square {
  --color: hsla(var(--hue, 0) var(--sat, 100%) var(--lig, 40%) / var(--opa, 1));
  color: var(--color);
  background-color: var(--color);
  border: 0.8vh var(--color) solid;
  border-color:
    hsla(var(--hue) 100% var(--lig, 65%) / var(--opa, 1))
    hsla(var(--hue) 100% var(--lig, 25%) / var(--opa, 1))
    hsla(var(--hue) 100% var(--lig, 25%) / var(--opa, 1))
    hsla(var(--hue) 100% var(--lig, 65%) / var(--opa, 1));
}

.user-pieces {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(3, auto);
  gap: 2vh 1vh;
  flex-direction: row;
  place-items: center;
}

.piece {
  height: 100%;
  width: 100%;
}

.piece-grid {
  width: min-content;
  margin: auto;
  display: grid;
  place-items: center;
  place-content: center;
}
.piece-grid.selected {
  position: absolute;
  top: 0;
  left: 0;
  transform: translate(var(--xt), var(--yt)) scale(1);
  pointer-events: none;
  touch-action: none;
}

.piece-grid .square {
  height: var(--square-size);
  width: var(--square-size);
  border-width: calc(var(--square-size) / 5)
}