/* ── Light theme (default) ── */
:root {
  --bg-page: #f5f2ec;
  --bg-gradient-a: rgba(29, 79, 145, 0.07);
  --bg-gradient-b: rgba(190, 168, 122, 0.09);
  --bg-content: rgba(255, 255, 255, 0.96);
  --bg-sidenav: rgba(255, 255, 255, 0.9);
  --border-color: #e6e0d6;
  --border-light: #d8d8d8;
  --divider-color: #cfc7bc;
  --heading-color: #143a67;
  --text-color: #4a4a4a;
  --text-secondary: #5e5e5e;
  --text-muted: #777777;
  --link-color: #1d4f91;
  --sidenav-text: #5d6570;
  --shadow-sidenav: 0 16px 36px rgba(31, 44, 62, 0.08);
  --shadow-content: 0 20px 56px rgba(31, 44, 62, 0.09);
  --shadow-photo: 0 10px 24px rgba(20, 58, 103, 0.08);
  --focus-ring: rgba(29, 79, 145, 0.25);
  --counter-color: #143a67;
}

/* ── Dark theme (manual toggle) ── */
[data-theme="dark"] {
  --bg-page: #111827;
  --bg-gradient-a: rgba(59, 130, 246, 0.06);
  --bg-gradient-b: rgba(168, 140, 90, 0.04);
  --bg-content: rgba(30, 41, 59, 0.97);
  --bg-sidenav: rgba(30, 41, 59, 0.92);
  --border-color: #2d3a4d;
  --border-light: #334155;
  --divider-color: #374151;
  --heading-color: #93c5fd;
  --text-color: #d1d5db;
  --text-secondary: #9ca3af;
  --text-muted: #6b7280;
  --link-color: #60a5fa;
  --sidenav-text: #9ca3af;
  --shadow-sidenav: 0 16px 36px rgba(0, 0, 0, 0.3);
  --shadow-content: 0 20px 56px rgba(0, 0, 0, 0.35);
  --shadow-photo: 0 10px 24px rgba(0, 0, 0, 0.25);
  --focus-ring: rgba(96, 165, 250, 0.3);
  --counter-color: #93c5fd;
}

/* ── Base ── */
body {
  margin: 0;
  padding: 0;
  background:
    radial-gradient(circle at top left, var(--bg-gradient-a), transparent 26%),
    radial-gradient(circle at bottom right, var(--bg-gradient-b), transparent 24%),
    var(--bg-page);
  background-color: var(--bg-page);
  color: var(--text-color);
  font: 18px/1.58 "Crimson Pro", Georgia, serif;
}

html {
  scroll-behavior: smooth;
}

a {
  color: var(--link-color);
  text-decoration: none;
}

a:hover,
a:focus-visible {
  text-decoration: underline;
}

img {
  max-width: 100%;
  display: block;
}

p,
ul {
  margin: 0 0 18px;
}

ul {
  padding-left: 24px;
}

li {
  margin-bottom: 8px;
}

h1,
h2 {
  margin: 0;
  color: var(--heading-color);
  font-weight: 600;
}

h1 {
  font-size: 2.1rem;
  line-height: 1.1;
  margin-bottom: 14px;
}

h2 {
  font-size: 1.5rem;
  line-height: 1.2;
  margin-top: 30px;
  margin-bottom: 14px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border-light);
}

.zh-song {
  font-family: "SimSun", "Songti SC", "STSong", serif;
}

.page {
  width: 100%;
  min-height: 100vh;
  padding: 32px 0 48px;
}

.layout {
  width: min(1280px, calc(100% - 32px));
  margin: 0 auto;
  display: grid;
  grid-template-columns: 180px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}

.side-nav {
  position: sticky;
  top: 32px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 18px 16px;
  background: var(--bg-sidenav);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sidenav);
  border-radius: 16px;
}

.side-nav-title {
  margin-bottom: 8px;
  color: var(--heading-color);
  font-size: 0.98rem;
  font-weight: 600;
  letter-spacing: 0.03em;
}

.side-nav a {
  display: block;
  padding: 6px 0;
  color: var(--sidenav-text);
  font-size: 1rem;
  line-height: 1.35;
}

.side-nav a:hover,
.side-nav a:focus-visible {
  color: var(--heading-color);
  text-decoration: none;
}

.content {
  width: 100%;
  margin: 0;
  padding: 34px 24px 56px;
  background: var(--bg-content);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-content);
  border-radius: 18px;
}

.intro {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: 24px;
  align-items: start;
  margin-bottom: 22px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border-color);
}

.intro-photo img {
  width: 180px;
  height: 240px;
  object-fit: cover;
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-photo);
}

.intro-text {
  min-width: 0;
}

.name-divider {
  width: 92px;
  height: 1px;
  margin: 0 0 18px;
  background: var(--divider-color);
}

.title-line {
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.title-line a {
  color: var(--link-color);
}

.section-block {
  scroll-margin-top: 28px;
}

.section-block + .section-block {
  margin-top: 4px;
}

.footer-note {
  margin-top: 34px;
  padding-top: 10px;
  border-top: 1px solid var(--border-light);
  color: var(--text-muted);
  font-size: 0.95rem;
}

a:focus-visible {
  outline: 2px solid var(--focus-ring);
  outline-offset: 3px;
}

/* ── Paper cards ── */
.paper-box {
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
  padding: 2em 0 2em 0;
}

.paper-box .paper-box-image {
  flex: 0 0 40%;
  display: flex;
  justify-content: center;
}

.paper-box .paper-box-image > div {
  position: relative;
}

.paper-box .paper-box-image .badge {
  padding-left: 1rem;
  padding-right: 1rem;
  position: absolute;
  margin-top: 0.5em;
  margin-left: -0.5em;
  color: #fff;
  background-color: #00369f;
  font-size: 0.8em;
}

.paper-box .paper-box-image img {
  max-width: 400px;
  box-shadow: 3px 3px 6px #888;
  object-fit: cover;
}

.paper-box .paper-box-text {
  flex: 1;
  padding-left: 2em;
}

.paper-box .paper-box-text p {
  margin: 0 0 8px;
}

.paper-box .paper-box-text a {
  color: var(--link-color);
}

.paper-box .paper-box-text ul {
  margin: 4px 0 0;
  padding-left: 18px;
}

.paper-box .paper-box-text ul li {
  color: var(--text-secondary);
  font-size: 0.93rem;
  line-height: 1.55;
}

@media (max-width: 559px) {
  .paper-box {
    flex-direction: column;
  }

  .paper-box .paper-box-image {
    flex: none;
    width: 100%;
    order: 2;
  }

  .paper-box .paper-box-text {
    flex: none;
    width: 100%;
    padding-left: 0;
    order: 1;
  }
}

/* ── Dark mode toggle ── */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--border-color);
}

.theme-toggle-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  width: 100%;
  padding: 6px 8px;
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--sidenav-text);
  font-family: "Crimson Pro", Georgia, serif;
  font-size: 0.9rem;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, border-color 0.2s;
}

.theme-toggle-btn:hover {
  background: rgba(128, 128, 128, 0.08);
  color: var(--heading-color);
  border-color: var(--heading-color);
}

.theme-toggle-btn .icon {
  font-size: 1rem;
  line-height: 1;
}

/* ── Visitor counter ── */
.visitor-counter {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-top: 6px;
  padding-top: 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.counter-icon {
  font-size: 1rem;
}

#visitor-count {
  font-weight: 500;
  color: var(--counter-color);
  font-family: "IBM Plex Mono", monospace;
  min-width: 40px;
}

/* ── Responsive: tablet ── */
@media print, screen and (max-width: 960px) {
  .layout {
    width: auto;
    grid-template-columns: 1fr;
    gap: 14px;
    margin: 0 14px;
  }

  .side-nav {
    position: static;
    flex-direction: row;
    flex-wrap: wrap;
    align-items: center;
    gap: 10px 16px;
  }

  .side-nav-title {
    width: 100%;
    margin-bottom: 0;
  }

  .content {
    width: auto;
    padding: 28px 18px 44px;
    margin: 0;
  }

  .theme-toggle {
    width: auto;
    margin-top: 0;
    padding-top: 0;
    border-top: none;
  }
}

/* ── Responsive: mobile ── */
@media print, screen and (max-width: 640px) {
  body {
    font-size: 17px;
  }

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

  .intro-photo img {
    width: 170px;
    height: 226px;
  }

  .page {
    padding-top: 18px;
  }

  .content {
    border-radius: 14px;
  }

  .side-nav {
    padding: 14px 14px 10px;
  }

  .visitor-counter {
    width: 100%;
    justify-content: center;
  }
}