:root {
  --teal-950: #123f43;
  --teal-800: #185b5c;
  --teal-700: #257572;
  --teal-200: #c9e1dc;
  --teal-100: #eaf5f2;
  --ink-soft: #627879;
  --line: rgba(25, 91, 92, 0.14);
  --page-gutter: clamp(20px, 4.5vw, 72px);
  --ui-font: "DM Sans", "Avenir Next", "Helvetica Neue", sans-serif;
  --editorial-font: "Newsreader", Georgia, serif;
  --chinese-font: "Noto Sans SC", "PingFang SC", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  position: relative;
  min-width: 320px;
  margin: 0;
  color: var(--teal-950);
  background:
    radial-gradient(circle at 12% 0, rgba(190, 224, 215, 0.32), transparent 31rem),
    linear-gradient(180deg, #fbfdfc, #f2f8f6 52rem);
  font-family: var(--ui-font);
  font-size: 16px;
  line-height: 1.5;
}

body::before {
  position: absolute;
  z-index: -1;
  top: 0;
  right: 0;
  left: 0;
  height: 315px;
  content: "";
  pointer-events: none;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.18), rgba(255, 255, 255, 0.72)),
    url("assets/brand/homepage-landscape-west-lake-full-v1.webp") center bottom / cover no-repeat;
  opacity: 0.72;
}

button,
a {
  font: inherit;
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 3px solid rgba(37, 117, 114, 0.28);
  outline-offset: 3px;
}

.learn-shell,
.site-footer {
  width: auto;
  margin-inline: var(--page-gutter);
}

.learn-shell {
  min-height: calc(100vh - 180px);
  padding: 16px 0 48px;
}

.learn-intro {
  display: flex;
  max-width: 1580px;
  margin: 0 auto 16px;
  align-items: end;
  justify-content: space-between;
  gap: 28px;
}

.learn-intro h1 {
  margin: 0;
  font-family: var(--editorial-font);
  font-size: clamp(2.15rem, 3.2vw, 3.25rem);
  font-weight: 600;
  letter-spacing: -0.035em;
  line-height: 1;
}

.learn-intro > div > p {
  margin: 8px 0 0;
  color: var(--ink-soft);
  font-size: 1rem;
}

.learning-categories {
  display: grid;
  max-width: 1580px;
  margin: 0 auto;
  grid-template-columns: repeat(8, minmax(0, 1fr));
  gap: 10px;
}

.category-button {
  position: relative;
  display: grid;
  min-width: 0;
  min-height: 190px;
  padding: 17px 10px 18px;
  place-items: center;
  align-content: center;
  gap: 5px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 11px;
  color: var(--teal-950);
  background: rgba(255, 255, 255, 0.9);
  cursor: pointer;
  text-align: center;
  transition: border-color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
}

.category-button::after {
  position: absolute;
  right: 0;
  bottom: 0;
  left: 0;
  height: 4px;
  content: "";
  background: var(--category-accent);
  opacity: 0;
}

.category-button:hover,
.category-button[aria-pressed="true"] {
  border-color: color-mix(in srgb, var(--category-accent) 64%, white);
  box-shadow: 0 14px 30px rgba(19, 66, 67, 0.09);
  transform: translateY(-3px);
}

.category-button[aria-pressed="true"]::after {
  opacity: 1;
}

.category-icon {
  display: grid;
  width: 78px;
  height: 78px;
  margin-bottom: 4px;
  place-items: center;
}

.category-icon img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.category-emoji {
  font-size: 3.2rem;
  line-height: 1;
}

.category-button strong {
  font-family: var(--chinese-font);
  font-size: 1rem;
  line-height: 1.25;
}

.category-button > span:last-child {
  color: color-mix(in srgb, var(--category-accent) 76%, var(--teal-950));
  font-family: var(--editorial-font);
  font-size: 0.98rem;
  font-weight: 600;
  line-height: 1.15;
}

.category-browser {
  max-width: 1580px;
  margin: 28px auto 0;
  padding-top: 26px;
  border-top: 1px solid var(--line);
  scroll-margin-top: 96px;
}

.selected-category {
  display: flex;
  align-items: center;
  gap: 14px;
}

.selected-icon {
  display: grid;
  width: 62px;
  height: 62px;
  flex: 0 0 auto;
  place-items: center;
}

.selected-icon img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.selected-icon .category-emoji {
  font-size: 2.7rem;
}

.selected-category h2 {
  display: flex;
  margin: 0;
  align-items: baseline;
  gap: 12px;
}

.selected-zh {
  font-family: var(--chinese-font);
  font-size: clamp(1.7rem, 2.6vw, 2.25rem);
  font-weight: 700;
  line-height: 1.15;
}

.selected-en {
  color: var(--teal-700);
  font-family: var(--editorial-font);
  font-size: clamp(1.45rem, 2vw, 1.9rem);
  font-weight: 600;
  line-height: 1.15;
}

.topic-prompt {
  margin: 22px 0 13px;
  color: var(--teal-700);
  font-size: 0.95rem;
  font-weight: 700;
}

.subcatalogs {
  display: grid;
  grid-template-columns: repeat(var(--selection-count, 1), minmax(0, 1fr));
  gap: 11px;
}

.subcatalog-button {
  display: grid;
  min-width: 0;
  min-height: 78px;
  padding: 13px 16px;
  place-content: center;
  gap: 2px;
  border: 1px solid var(--line);
  border-radius: 9px;
  color: var(--teal-950);
  background: rgba(255, 255, 255, 0.92);
  cursor: pointer;
  text-align: center;
  transition: border-color 160ms ease, box-shadow 160ms ease, color 160ms ease,
    background 160ms ease, transform 160ms ease;
}

.subcatalog-button strong {
  font-family: var(--chinese-font);
  font-size: 1rem;
  line-height: 1.25;
}

.subcatalog-button span {
  color: var(--ink-soft);
  font-family: var(--editorial-font);
  font-size: 0.96rem;
  font-weight: 600;
  line-height: 1.2;
}

.subcatalog-button:hover,
.subcatalog-button[aria-pressed="true"] {
  border-color: var(--teal-700);
  color: #fff;
  background: var(--teal-700);
  box-shadow: 0 10px 24px rgba(19, 66, 67, 0.12);
  transform: translateY(-2px);
}

.subcatalog-button:hover span,
.subcatalog-button[aria-pressed="true"] span {
  color: rgba(255, 255, 255, 0.88);
}

.topic-results-heading {
  display: flex;
  margin: 27px 0 13px;
  align-items: baseline;
  gap: 12px;
}

.topic-results-heading > span {
  color: var(--teal-700);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.15em;
}

.topic-results-heading h3 {
  margin: 0;
  font-family: var(--editorial-font);
  font-size: clamp(1.3rem, 2vw, 1.7rem);
  font-weight: 600;
  line-height: 1.15;
}

.topic-results-heading h3:empty {
  display: none;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 13px;
}

.topic-card {
  position: relative;
  display: flex;
  min-height: 142px;
  padding: 20px 54px 19px 20px;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: 10px;
  color: var(--teal-950);
  background: rgba(255, 255, 255, 0.92);
  box-shadow: 0 8px 22px rgba(19, 66, 67, 0.05);
  text-decoration: none;
  transition: border-color 160ms ease, box-shadow 160ms ease, transform 160ms ease;
}

.topic-card:hover {
  border-color: color-mix(in srgb, var(--category-accent) 48%, white);
  box-shadow: 0 14px 30px rgba(19, 66, 67, 0.1);
  transform: translateY(-3px);
}

.topic-copy {
  display: grid;
  min-width: 0;
  gap: 3px;
}

.topic-copy strong {
  font-family: var(--chinese-font);
  font-size: 1.16rem;
  line-height: 1.25;
}

.topic-copy > span {
  color: color-mix(in srgb, var(--category-accent) 78%, var(--teal-950));
  font-family: var(--editorial-font);
  font-size: 1.16rem;
  font-weight: 600;
  line-height: 1.2;
}

.topic-copy small {
  margin-top: 5px;
  color: var(--ink-soft);
  font-size: 0.83rem;
  line-height: 1.35;
}

.topic-arrow {
  position: absolute;
  top: 50%;
  right: 17px;
  display: grid;
  width: 30px;
  height: 30px;
  place-items: center;
  border-radius: 50%;
  color: #fff;
  background: var(--category-accent);
  font-size: 1rem;
  transform: translateY(-50%);
}

.site-footer {
  display: flex;
  padding: 20px 4px 28px;
  align-items: center;
  justify-content: center;
  gap: 12px;
  border-top: 1px solid var(--line);
}

.site-footer img {
  width: 44px;
  height: 44px;
  flex: 0 0 auto;
  object-fit: contain;
}

.site-footer div {
  display: grid;
  justify-items: start;
  color: var(--ink-soft);
  font-size: 0.78rem;
  text-align: left;
}

.site-footer strong {
  color: #456566;
  font-size: 0.86rem;
}

@media (max-width: 1340px) {
  .learning-categories {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .category-button {
    min-height: 150px;
    padding: 12px 10px 13px;
  }

  .category-icon {
    width: 68px;
    height: 68px;
    margin-bottom: 2px;
  }

  .topic-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 920px) {
  .learn-shell {
    padding-top: 16px;
  }

  .subcatalogs[data-selection-count="4"],
  .subcatalogs[data-selection-count="5"] {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .topic-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 680px) {
  body::before {
    height: 360px;
  }

  .learn-intro {
    align-items: start;
    flex-direction: column;
    gap: 16px;
  }

  .learn-intro h1 {
    font-size: clamp(2.1rem, 10vw, 2.85rem);
  }

  .learning-categories {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .category-button {
    min-height: 148px;
  }

  .category-icon {
    width: 60px;
    height: 60px;
  }

  .selected-category {
    align-items: flex-start;
  }

  .selected-category h2 {
    display: grid;
    gap: 1px;
  }

  .selected-icon {
    width: 54px;
    height: 54px;
  }

  .subcatalogs[data-selection-count="3"],
  .subcatalogs[data-selection-count="4"],
  .subcatalogs[data-selection-count="5"] {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .topic-grid {
    grid-template-columns: 1fr;
  }

  .topic-card {
    min-height: 124px;
  }
}

@media (max-width: 460px) {
  .subcatalogs {
    grid-template-columns: 1fr;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}