/* ============================================================
   四季品牌站 — 共享站点样式 /assets/site.css
   纸感手账 × 技术蓝图网格 × 四季色轮转
   ============================================================ */

/* ---------- 1. reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body, h1, h2, h3, h4, h5, p, ul, ol, li, figure, figcaption, blockquote, dl, dd, hr { margin: 0; }
ul, ol { padding: 0; list-style: none; }
button { font: inherit; color: inherit; background: none; border: 0; padding: 0; }
a { color: inherit; }
img, svg { display: block; max-width: 100%; }
hr { border: 0; }
summary { cursor: pointer; }

/* ---------- 2. tokens ---------- */
:root {
  --paper: #F7F1E6;
  --paper-2: #EDE3D0;
  --ink: #241F1C;
  --ink-soft: #5D5349;
  --spring: #7FAE7A;
  --spring-pink: #E7C6CC;
  --summer: #4E8FA8;
  --summer-yellow: #E5B84A;
  --autumn: #BE6338;
  --autumn-gold: #D6B16C;
  --winter: #2D4A5D;
  --frost: #DDE7E7;

  --line: rgba(36, 31, 28, 0.12);
  --line-strong: rgba(36, 31, 28, 0.26);
  --shadow-soft: 0 14px 34px rgba(36, 31, 28, 0.08);

  --radius-lg: 26px;
  --radius: 18px;
  --radius-sm: 12px;
  --pill: 999px;

  --shell: 1240px;
  --gutter: 24px;
  --gap: 24px;
  --stack: 16px;

  --header-offset: 112px;

  --font-serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "SimSun", serif;
  --font-sans: "Noto Sans SC", "Source Han Sans SC", -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

/* 季节语义色：任何元素加 data-season 即可获得 --season */
[data-season="spring"] { --season: var(--spring); }
[data-season="summer"] { --season: var(--summer); }
[data-season="autumn"] { --season: var(--autumn); }
[data-season="winter"] { --season: var(--winter); }

/* ---------- 3. base typography ---------- */
body {
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.75;
  color: var(--ink);
  background-color: var(--paper);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  line-height: 1.28;
  letter-spacing: 0.01em;
  color: var(--ink);
}
h1 { font-size: clamp(34px, 5vw, 56px); }
h2 { font-size: clamp(26px, 3.4vw, 40px); }
h3 { font-size: clamp(20px, 2.2vw, 28px); }
h4 { font-size: 20px; }
strong { font-weight: 600; }
small { font-size: 13px; }
::selection { background: var(--spring-pink); color: var(--ink); }

:focus-visible {
  outline: 2px solid var(--summer);
  outline-offset: 3px;
  box-shadow: 0 0 0 3px var(--paper);
  border-radius: 8px;
}
:focus:not(:focus-visible) { outline: none; }

/* ---------- 4. layout primitives ---------- */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.section { padding-block: clamp(48px, 7vw, 96px); }
.section--tight { padding-block: clamp(32px, 4vw, 56px); }
.overlap-top {
  margin-top: calc(-1 * var(--header-offset));
  padding-top: calc(var(--header-offset) + 24px);
}
.stack { display: flex; flex-direction: column; gap: var(--stack); }
.grid { display: grid; gap: var(--gap); }
.grid--split { grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); }
.grid--halves { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--thirds { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.rule { height: 1px; background: var(--line); border: 0; margin-block: clamp(24px, 4vw, 44px); }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink-soft);
}
.eyebrow::before {
  content: "";
  width: 26px;
  height: 2px;
  border-radius: 2px;
  background: var(--season, var(--autumn));
}
.page-no {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--ink-soft);
}

/* ---------- 5. buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 13px 24px;
  border-radius: var(--pill);
  border: 1px solid transparent;
  font-family: var(--font-sans);
  font-size: 15px;
  font-weight: 500;
  letter-spacing: 0.02em;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.25s ease, color 0.25s ease, border-color 0.25s ease, transform 0.25s ease;
}
.btn:hover { transform: translateY(-1px); }
.btn--primary { background: var(--ink); color: var(--paper); }
.btn--primary:hover { background: #3A322C; color: var(--paper); }
.btn--outline { background: transparent; color: var(--ink); border-color: var(--line-strong); }
.btn--outline:hover { background: var(--paper-2); border-color: var(--ink); }
.btn--quiet {
  padding: 6px 0;
  border-radius: 0;
  color: var(--ink);
  border-bottom: 2px solid var(--season, var(--autumn));
}
.btn--quiet:hover { transform: none; background: transparent; color: var(--autumn); }

/* ---------- 6. tags / chips / cards ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  border-radius: var(--pill);
  border: 1px solid var(--line-strong);
  background: var(--paper);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--ink-soft);
}
.season-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 14px 4px 10px;
  border-radius: var(--pill);
  background: var(--paper-2);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--ink);
}
.season-chip::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--chip, var(--ink-soft));
}
.season-chip--spring { --chip: var(--spring); background: #E7C6CC55; }
.season-chip--summer { --chip: var(--summer); background: #4E8FA822; }
.season-chip--autumn { --chip: var(--autumn); background: #D6B16C44; }
.season-chip--winter { --chip: var(--winter); background: #DDE7E799; }

.card {
  position: relative;
  overflow: hidden;
  padding: clamp(20px, 2.4vw, 28px);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--paper);
}
.card[data-season]::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 3px;
  background: var(--season);
}
.card--tint { background: var(--paper-2); }

/* ---------- 7. fold panels ---------- */
.panel {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  overflow: hidden;
}
.panel + .panel { margin-top: 10px; }
.panel > summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 20px;
  font-family: var(--font-serif);
  font-size: 18px;
  font-weight: 600;
  list-style: none;
  transition: background-color 0.3s ease;
}
.panel > summary::-webkit-details-marker { display: none; }
.panel > summary:hover { background: var(--paper-2); }
.panel > summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 16px;
  color: var(--ink-soft);
}
.panel[open] > summary { background: var(--paper-2); }
.panel[open] > summary::after { content: "–"; color: var(--autumn); }
.panel-body {
  padding: 4px 20px 20px;
  color: var(--ink-soft);
  animation: panel-in 0.3s ease both;
}
@keyframes panel-in {
  from { opacity: 0; transform: translateY(-6px); }
  to { opacity: 1; transform: none; }
}

/* ---------- 8. breadcrumbs & prose ---------- */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
}
.crumbs li { display: inline-flex; align-items: center; gap: 8px; }
.crumbs li + li::before { content: "/"; color: var(--line-strong); }
.crumbs a { text-decoration: none; border-bottom: 1px solid var(--line-strong); }
.crumbs a:hover { border-bottom-color: var(--autumn); color: var(--ink); }

.prose { max-width: 68ch; color: var(--ink); }
.prose > * + * { margin-top: 1em; }
.prose h2, .prose h3 { margin-top: 1.6em; }
.prose ul, .prose ol { padding-left: 1.3em; list-style: disc; }
.prose ol { list-style: decimal; }
.prose li + li { margin-top: 0.4em; }
.prose a {
  color: var(--ink);
  text-decoration: none;
  border-bottom: 2px solid var(--spring);
}
.prose a:hover { color: var(--autumn); border-bottom-color: var(--autumn); }
.prose blockquote {
  padding-left: 18px;
  border-left: 3px solid var(--autumn-gold);
  color: var(--ink-soft);
}

/* ---------- 9. image frames ---------- */
.media-frame {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background:
    repeating-linear-gradient(135deg, rgba(36, 31, 28, 0.045) 0 1px, transparent 1px 12px),
    var(--paper-2);
}
.media-frame > img { width: 100%; height: 100%; object-fit: cover; }
.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 4 / 5; }
.media-caption {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
}

/* ---------- 10. header ---------- */
.skip-link {
  position: absolute;
  left: 12px;
  top: -80px;
  z-index: 200;
  padding: 10px 18px;
  border-radius: var(--pill);
  background: var(--ink);
  color: var(--paper);
  font-size: 14px;
  text-decoration: none;
  transition: top 0.25s ease;
}
.skip-link:focus-visible { top: 10px; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  color: var(--ink);
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background-color 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
}
.site-header[data-scrolled="true"],
.site-header--solid {
  background: var(--paper);
  border-bottom-color: var(--line);
  box-shadow: 0 8px 22px rgba(36, 31, 28, 0.06);
}

.header-index {
  display: flex;
  align-items: center;
  gap: 14px;
  padding-block: 12px 0;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--ink-soft);
}
.index-mark { color: var(--ink); letter-spacing: 0.2em; }
.index-line { flex: 1; height: 1px; background: var(--line-strong); }
.index-note { white-space: nowrap; }
.index-note--right { color: var(--autumn); }

.header-main {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  align-items: center;
  gap: 28px;
  padding-block: 14px 16px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--ink);
  min-width: 0;
}
.brand-seal {
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  flex: 0 0 auto;
  border: 1px solid var(--line-strong);
  border-radius: 14px;
  background: linear-gradient(150deg, var(--spring-pink), var(--frost));
  font-family: var(--font-serif);
  font-size: 19px;
  font-weight: 600;
  color: var(--ink);
}
.brand-text { display: flex; flex-direction: column; gap: 2px; min-width: 0; }
.brand-name {
  font-family: var(--font-serif);
  font-size: 21px;
  font-weight: 600;
  letter-spacing: 0.12em;
  line-height: 1.2;
}
.brand-sign {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--ink-soft);
}

.primary-nav {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 18px;
  min-width: 0;
}
.nav-list { display: flex; align-items: center; gap: 2px; flex-wrap: wrap; }
.nav-link {
  position: relative;
  display: inline-block;
  padding: 9px 14px;
  border-radius: var(--pill);
  font-size: 15px;
  line-height: 1.3;
  color: var(--ink-soft);
  text-decoration: none;
  transition: color 0.2s ease, background-color 0.2s ease;
}
.nav-link::after {
  content: "";
  position: absolute;
  left: 14px;
  right: 14px;
  bottom: 4px;
  height: 3px;
  border-radius: 3px;
  background: var(--season, var(--autumn));
  opacity: 0;
  transform: scaleX(0.4);
  transform-origin: left center;
  transition: opacity 0.25s ease, transform 0.25s ease;
}
.nav-link:hover { color: var(--ink); background: rgba(237, 227, 208, 0.7); }
.nav-link:hover::after { opacity: 0.45; transform: scaleX(1); }
.nav-link[aria-current="page"] { color: var(--ink); font-weight: 500; }
.nav-link[aria-current="page"]::after { opacity: 1; transform: scaleX(1); }

.nav-utility {
  display: flex;
  align-items: center;
  gap: 14px;
  padding-left: 18px;
  border-left: 1px solid var(--line);
}
.utility-link {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
  white-space: nowrap;
  transition: color 0.2s ease, border-color 0.2s ease;
}
.utility-link:hover { color: var(--ink); border-bottom-color: var(--summer); }

.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 9px 16px;
  border: 1px solid var(--line-strong);
  border-radius: var(--pill);
  background: var(--paper);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--ink);
  cursor: pointer;
}
.nav-toggle-bars { display: inline-flex; flex-direction: column; gap: 4px; width: 16px; }
.nav-toggle-bars span { display: block; height: 1.5px; background: var(--ink); border-radius: 2px; transition: transform 0.25s ease; }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars span:first-child { transform: translateY(3px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars span:last-child { transform: translateY(-2.5px) rotate(-45deg); }
.nav-toggle-label { line-height: 1; }

/* 侧边翻阅标签 */
.season-rail {
  position: fixed;
  right: 0;
  top: 40%;
  z-index: 80;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.rail-tab {
  display: block;
  writing-mode: vertical-rl;
  padding: 16px 9px;
  border: 1px solid var(--line-strong);
  border-right: 0;
  border-left: 4px solid var(--rail, var(--line-strong));
  border-radius: 14px 0 0 14px;
  background: var(--paper);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.24em;
  color: var(--ink);
  text-decoration: none;
  transition: background-color 0.25s ease, transform 0.25s ease;
}
.rail-tab:hover { background: var(--paper-2); transform: translateX(-3px); }
.rail-tab--spring { --rail: var(--spring); }
.rail-tab--summer { --rail: var(--summer); }
.rail-tab--autumn { --rail: var(--autumn); }
.rail-tab--winter { --rail: var(--winter); }

/* ---------- 11. footer ---------- */
.site-footer {
  margin-top: clamp(40px, 6vw, 80px);
  padding-top: 8px;
  background: var(--paper);
  border-top: 1px solid var(--line);
}
.footer-swatches {
  display: flex;
  gap: 6px;
  max-width: var(--shell);
  margin-inline: auto;
  padding: 22px var(--gutter) 0;
}
.footer-swatch { flex: 1; height: 6px; border-radius: var(--pill); }
.footer-swatch--spring { background: var(--spring); }
.footer-swatch--summer { background: var(--summer); }
.footer-swatch--autumn { background: var(--autumn); }
.footer-swatch--winter { background: var(--winter); }

.footer-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) repeat(3, minmax(0, 0.6fr));
  gap: 32px;
  padding-block: clamp(28px, 4vw, 48px);
}
.footer-wordmark {
  font-family: var(--font-serif);
  font-size: clamp(22px, 2.4vw, 28px);
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--ink);
}
.footer-line {
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
  line-height: 1.9;
}
.footer-quick { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 18px; }

.footer-col-title {
  display: flex;
  align-items: center;
  gap: 8px;
  padding-bottom: 10px;
  margin-bottom: 10px;
  border-bottom: 1px solid var(--line);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--ink-soft);
}
.footer-col-title::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--season, var(--ink-soft));
}
.footer-list { display: flex; flex-direction: column; gap: 6px; }
.footer-link {
  display: inline-block;
  font-size: 15px;
  color: var(--ink);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  padding-bottom: 1px;
  transition: color 0.2s ease, border-color 0.2s ease;
}
.footer-link:hover { color: var(--autumn); border-bottom-color: var(--autumn); }

.footer-base {
  background: var(--winter);
  color: var(--frost);
  border-radius: 28px 28px 0 0;
  padding-block: clamp(28px, 4vw, 44px) 22px;
}
.footer-base-inner {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 28px;
}
.footer-contact { min-width: 0; }
.footer-label {
  margin-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: rgba(221, 231, 231, 0.66);
}
.contact-value {
  font-size: 15px;
  line-height: 1.9;
  color: var(--frost);
  overflow-wrap: anywhere;
}
.contact-value--wide { font-size: 14px; color: rgba(221, 231, 231, 0.82); }
.footer-note {
  font-size: 13.5px;
  line-height: 1.85;
  color: rgba(221, 231, 231, 0.78);
}
.footer-legal-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px;
  margin-top: 26px;
  padding-top: 16px;
  border-top: 1px solid rgba(221, 231, 231, 0.22);
}
.footer-legal {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: rgba(221, 231, 231, 0.72);
}
.footer-legal--right { color: rgba(221, 231, 231, 0.5); }

/* ---------- 12. reveal ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.5s ease, transform 0.5s ease;
  will-change: opacity, transform;
}
[data-reveal].is-in { opacity: 1; transform: none; }

/* ---------- 13. responsive ---------- */
@media (max-width: 1100px) {
  .nav-utility { display: none; }
  .season-rail { display: none; }
  .primary-nav { gap: 4px; }
}

@media (max-width: 960px) {
  :root { --header-offset: 84px; --gap: 18px; }
  body { font-size: 16px; }
  .header-main { grid-template-columns: minmax(0, 1fr) auto; gap: 12px; padding-block: 12px; }
  .brand-sign { display: none; }
  .nav-toggle { display: inline-flex; }

  .primary-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    max-height: calc(100vh - 96px);
    overflow-y: auto;
    padding: 10px var(--gutter) 22px;
    background: var(--paper);
    border-top: 1px solid var(--line);
    border-bottom: 1px solid var(--line);
    box-shadow: 0 18px 30px rgba(36, 31, 28, 0.1);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s ease;
  }
  .primary-nav[data-open="true"] { opacity: 1; visibility: visible; transform: none; }

  .nav-list { flex-direction: column; align-items: stretch; gap: 0; }
  .nav-link {
    display: block;
    padding: 13px 8px;
    border-radius: var(--radius-sm);
    border-bottom: 1px dashed var(--line);
    font-size: 17px;
    color: var(--ink);
  }
  .nav-link::after { display: none; }
  .nav-link:hover { background: var(--paper-2); }
  .nav-link[aria-current="page"] { background: var(--paper-2); box-shadow: inset 3px 0 0 var(--season, var(--autumn)); }

  .nav-utility {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    margin-top: 16px;
    padding: 16px 0 0;
    border-left: 0;
    border-top: 1px solid var(--line);
  }
  .utility-link { font-size: 12px; letter-spacing: 0.12em; }

  .header-index { font-size: 10px; letter-spacing: 0.1em; padding-block: 8px 0; }
  .index-note--right { display: none; }

  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-brand { grid-column: 1 / -1; }
  .footer-base-inner { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-contact--note { grid-column: 1 / -1; }
  .grid--split, .grid--halves { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 560px) {
  :root { --gutter: 18px; }
  .brand-seal { width: 34px; height: 34px; border-radius: 12px; font-size: 17px; }
  .brand-name { font-size: 18px; letter-spacing: 0.08em; }
  .footer-grid { grid-template-columns: minmax(0, 1fr); gap: 22px; }
  .footer-base-inner { grid-template-columns: minmax(0, 1fr); gap: 20px; }
  .footer-legal-bar { flex-direction: column; }
  .media-frame--tall { aspect-ratio: 3 / 4; }
}

/* ---------- 14. reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  [data-reveal] { opacity: 1; transform: none; }
  .btn:hover, .rail-tab:hover { transform: none; }
}