chess/assets/css/_board.scss

:root {
  --board-size: 90vmin;
}

@media (min-aspect-ratio: 10/11) {
  :root {
    --board-size: 80vmin;
  }
}

@mixin move-indicator {
  border-radius: 50%;
  content: "";
  display: block;
  height: 2%;
  position: absolute;
  right: 2%;
  width: 2%;
}

.board {
  background: lighten($black-square-color, 7%);
  border-collapse: unset;
  border-radius: 2.8%;
  border-spacing: 1px;
  box-shadow: 0 (var(--board-size) / 200) (var(--board-size) / 40) $board-shadow-color;
  color: $white-square-color;
  height: var(--board-size);
  padding: calc(var(--board-size) / 20);
  position: relative;
  width: var(--board-size);

  &.white-to-move::before {
    @include move-indicator;
    background: $white;
  }

  &.black-to-move::before {
    @include move-indicator;
    background: $black;
  }

  &.player-is-white.white-to-move::before,
  &.player-is-black.black-to-move::before {
    bottom: 2%;
  }

  &.player-is-white.black-to-move::before,
  &.player-is-black.white-to-move::before {
    top: 2%;
  }

  .board-rank-labels,
  .board-file-labels {
    display: none;
  }

  &.player-is-white {
    .board-rank-labels {
      display: flex;
      flex-direction: column-reverse;
    }

    .board-file-labels {
      display: flex;
      flex-direction: row;
    }
  }

  &.player-is-black {
    .board-rank-labels {
      display: flex;
      flex-direction: column;
    }

    .board-file-labels {
      display: flex;
      flex-direction: row-reverse;
    }
  }
}

.board-rank-labels {
  display: flex;
  height: 90%;
  left: 0;
  position: absolute;
  width: 5%;
}

.board-file-labels {
  display: flex;
  height: 5%;
  position: absolute;
  top: 0;
  width: 90%;
}

.board-game-state {
  bottom: 0;
  color: white;
  height: 5%;
  position: absolute;
  width: 90%;
}

.board-label {
  align-items: center;
  display: flex;
  flex-grow: 1;
  font-size: calc(var(--board-size) / 40);
  justify-content: center;
}

.board-body {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);

  height: 100%;
  width: 100%;
}

%black-square {
  background-color: $black-square-color;

  &.selected {
    background-color: mix($black-square-color, $selected-square-color, 60%);
    box-shadow: inset 0 0 0 calc(var(--board-size) / 400) $selected-outline-color;
  }

  &.available {
    background-color: mix($black-square-color, $available-square-color, 80%);
    box-shadow: inset 0 0 0 calc(var(--board-size) / 400) $available-outline-color;
  }
}

%white-square {
  background-color: $white-square-color;

  &.selected {
    background-color: mix($white-square-color, $selected-square-color, 60%);
    box-shadow: inset 0 0 0 calc(var(--board-size) / 400) $selected-outline-color;
  }

  &.available {
    background-color: mix($white-square-color, $available-square-color, 80%);
    box-shadow: inset 0 0 0 calc(var(--board-size) / 400) $available-outline-color;
  }
}

.board-square {
  background-position: center;
  background-repeat: no-repeat;
  background-size: 100%;
  border-radius: 2%;
  margin: 0.5px;

  // This is to ensure the squares can be clicked on in PhantomJS
  // TODO: Figure out why we need this

  min-height: 20px;
  min-width: 20px;

  @include odd-between(1, 8) { @extend %white-square; }
  @include even-between(1, 8) { @extend %black-square; }

  @include odd-between(9, 16) { @extend %black-square; }
  @include even-between(9, 16) { @extend %white-square; }

  @include odd-between(17, 24) { @extend %white-square; }
  @include even-between(17, 24) { @extend %black-square; }

  @include odd-between(25, 32) { @extend %black-square; }
  @include even-between(25, 32) { @extend %white-square; }

  @include odd-between(33, 40) { @extend %white-square; }
  @include even-between(33, 40) { @extend %black-square; }

  @include odd-between(41, 48) { @extend %black-square; }
  @include even-between(41, 48) { @extend %white-square; }

  @include odd-between(49, 56) { @extend %white-square; }
  @include even-between(49, 56) { @extend %black-square; }

  @include odd-between(57, 64) { @extend %black-square; }
  @include even-between(57, 64) { @extend %white-square; }

  @each $colour in $colours {
    @each $piece in $pieces {
      &.#{$colour}.#{$piece} {
        background-image: url(/images/#{$piece}_#{$colour}.svg);
      }
    }
  }
}

@media (min-width: 480px) {
  .board-body {
    grid-gap: 1px;
  }
}

@media (min-width: 768px) {
  .board-body {
    grid-gap: 2px;
  }
}