:root {
  --letter-a-color: red;
  --letter-b-color: #3f97f6;
  --letter-c-color: #fbff00;
  --letter-d-color: #fbff00;
  --letter-e-color: #fbff00;
  --letter-f-color: #2ac427;
  --letter-g-color: #3f97f6;
  --letter-h-color: #0d31c2;
  --letter-i-color: #dd0bd9;
  --letter-j-color: #b766f1;
  --letter-k-color: #dd0bd9;
  --letter-l-color: #000;
  --letter-m-color: #b766f1;
  --letter-n-color: #0d31c2;
  --letter-o-color: #000;
  --letter-p-color: #fff;
  --letter-q-color: red;
  --letter-r-color: #2ac427;
  --letter-s-color: #ff9100;
  --letter-t-color: #3f97f6;
  --letter-u-color: #b766f1;
  --letter-v-color: #2ac427;
  --letter-w-color: #ff9100;
  --letter-x-color: #ff9100;
  --letter-y-color: #0d31c2;
  --letter-z-color: red;
}

@keyframes box-flash {
  0% {
    background: #fff;
    transform: scale(1.15);
  }

  100% {
    background: #e8cdcd;
    transform: scale(1);
  }
}

#game-container {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  background: gray;
  font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Arial, sans-serif;
  color: #e8f0ff;
  overflow: hidden;

  &:has(.overlay-start.hidden):before {
    content: "";
    position: absolute;
    top: 175px;
    left: 0;
    width: 100%;
    height: 135px;
    background-color: #4a4a4a;
    background-image: repeating-linear-gradient(-45deg, #0000, #0000 20px, #ffffff14 20px 30px);
    background-size: 60px 60px;
    background-position: var(--belt-offset, 0px) 0;
  }

  &:has(.overlay-start.hidden) .lives {
    display: flex;
  }

  &:has(.overlay-start.hidden) .speed-display {
    display: block;
  }

  &:has(.overlay-start.hidden):not(:has(.overlay-game-over:not(.hidden))) .boxes-row {
    display: flex;
  }

  & .overlay {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;

    &.hidden {
      display: none;
    }
  }

  & .overlay-start {
    background: #0d1520;
    top: 0;
    left: 0;
    transform: none;
    width: 100%;
    height: 100%;
    justify-content: center;
    z-index: 50;
  }

  & .overlay-game-over {
    z-index: 50;
  }

  & .conveyor-letters {
    position: absolute;
    top: 175px;
    left: 0;
    width: 100%;
    height: 135px;
    overflow: hidden;
    pointer-events: none;
  }

  & .conveyor-letter {
    position: absolute;
    top: 50%;
    left: 0;
    font-size: 100px;
    font-weight: bold;
  }

  & .lives {
    display: none;
    position: absolute;
    top: 80px;
    left: 50%;
    transform: translateX(-50%);
    gap: 8px;
  }

  & .heart {
    font-size: 36px;
    color: #e03030;
  }

  & .heart-lost {
    color: #555;
  }

  & .speed-display {
    display: none;
    position: absolute;
    top: 128px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 14px;
    color: #c8d6e8;
    letter-spacing: .05em;
  }

  & .boxes-row {
    display: none;
    position: absolute;
    left: 0;
    width: 100%;
    justify-content: center;
    align-items: center;
    gap: 6px;
  }

  & .boxes-row-1 {
    top: 520px;
  }

  & .boxes-row-2 {
    top: 630px;
  }

  & .boxes-row-3 {
    top: 740px;
  }

  & .box {
    width: 100px;
    height: 100px;
    background: #e8cdcd;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 60px;
    font-weight: bold;

    &.box-lit {
      animation: .3s ease-out forwards box-flash;
    }

    &[data-letter="A"] {
      color: var(--letter-a-color);
    }

    &[data-letter="B"] {
      color: var(--letter-b-color);
    }

    &[data-letter="C"] {
      color: var(--letter-c-color);
    }

    &[data-letter="D"] {
      color: var(--letter-d-color);
    }

    &[data-letter="E"] {
      color: var(--letter-e-color);
    }

    &[data-letter="F"] {
      color: var(--letter-f-color);
    }

    &[data-letter="G"] {
      color: var(--letter-g-color);
    }

    &[data-letter="H"] {
      color: var(--letter-h-color);
    }

    &[data-letter="I"] {
      color: var(--letter-i-color);
    }

    &[data-letter="J"] {
      color: var(--letter-j-color);
    }

    &[data-letter="K"] {
      color: var(--letter-k-color);
    }

    &[data-letter="L"] {
      color: var(--letter-l-color);
    }

    &[data-letter="M"] {
      color: var(--letter-m-color);
    }

    &[data-letter="N"] {
      color: var(--letter-n-color);
    }

    &[data-letter="O"] {
      color: var(--letter-o-color);
    }

    &[data-letter="P"] {
      color: var(--letter-p-color);
    }

    &[data-letter="Q"] {
      color: var(--letter-q-color);
    }

    &[data-letter="R"] {
      color: var(--letter-r-color);
    }

    &[data-letter="S"] {
      color: var(--letter-s-color);
    }

    &[data-letter="T"] {
      color: var(--letter-t-color);
    }

    &[data-letter="U"] {
      color: var(--letter-u-color);
    }

    &[data-letter="V"] {
      color: var(--letter-v-color);
    }

    &[data-letter="W"] {
      color: var(--letter-w-color);
    }

    &[data-letter="X"] {
      color: var(--letter-x-color);
    }

    &[data-letter="Y"] {
      color: var(--letter-y-color);
    }

    &[data-letter="Z"] {
      color: var(--letter-z-color);
    }
  }

  & .title {
    font-size: 64px;
    font-weight: bold;
    color: #e8f0ff;
    text-shadow: 0 2px 8px #4a6fa599;
  }

  & .instructions {
    font-size: 20px;
    color: #c8d6e8;
    text-align: center;
    line-height: 1.6;
  }

  & .btn {
    cursor: pointer;
    border: none;
    border-radius: 8px;
    color: #fff;
    font-weight: 600;
    transition: all .2s;
  }

  & .btn-start {
    padding: 14px 28px;
    font-size: 20px;
    background: #4a6fa5;

    &:hover {
      background: #5a7fb5;
      transform: translateY(-2px);
    }

    &:active {
      background: #3a5f95;
      transform: translateY(0);
    }
  }

  & .difficulty-row {
    display: flex;
    gap: 16px;
  }

  & .btn-difficulty {
    padding: 12px 28px;
    font-size: 18px;
    background: #2a3a52;
    border: 2px solid #0000;

    &:hover {
      background: #344d6e;
    }
  }

  & .btn-difficulty-selected {
    border-color: #5a9af0;
    background: #1e3560;
  }

  & .difficulty-description {
    font-size: 14px;
    color: #8aafd4;
    height: 20px;
    opacity: 0;
    transition: opacity .15s;
  }

  & .difficulty-description-visible {
    opacity: 1;
  }
}