:root {
  --bg-start: #e6f7ff;
  --bg-mid: #f3fbff;
  --bg-end: #fff5eb;
  --ink: #23354d;
  --muted: #63778f;
  --paper: rgba(255, 255, 255, 0.94);
  --paper-soft: rgba(255, 255, 255, 0.84);
  --paper-border: rgba(112, 205, 255, 0.14);
  --paper-shadow: 0 22px 56px rgba(69, 96, 130, 0.12);
  --paper-shadow-soft: 0 12px 28px rgba(69, 96, 130, 0.08);
  --sky: #61cfff;
  --sky-deep: #3397ff;
  --sea: #44e3cf;
  --lime: #d8ff57;
  --lime-deep: #ace600;
  --amber: #ffcf5a;
  --label: #c9b94a;
  --line: rgba(84, 117, 151, 0.12);
  --control-bg: rgba(255, 255, 255, 0.9);
  --control-active: linear-gradient(135deg, var(--sky), var(--lime));
  --control-text: #667b92;
  --toc-bg: rgba(255, 255, 255, 0.86);
  --toc-active: rgba(97, 207, 255, 0.12);
  --radius-xl: 30px;
  --radius-lg: 22px;
  --width: 1200px;
  --toc-width: 248px;
  --sans: "Avenir Next", "PingFang TC", "PingFang SC", "Microsoft JhengHei", "Microsoft YaHei", "Noto Sans TC", "Noto Sans SC", sans-serif;
  --serif: "Iowan Old Style", "Palatino Linotype", "Noto Serif TC", "Noto Serif SC", serif;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --bg-start: #081424;
  --bg-mid: #0f1b31;
  --bg-end: #17253f;
  --ink: #eef6ff;
  --muted: #aab9cf;
  --paper: rgba(17, 29, 47, 0.94);
  --paper-soft: rgba(18, 30, 49, 0.84);
  --paper-border: rgba(255, 255, 255, 0.08);
  --paper-shadow: 0 26px 68px rgba(5, 10, 18, 0.42);
  --paper-shadow-soft: 0 16px 36px rgba(5, 10, 18, 0.24);
  --sky: #67d5ff;
  --sky-deep: #43a3ff;
  --sea: #4ae7d4;
  --lime: #dbff63;
  --lime-deep: #bdf20c;
  --amber: #ffd96a;
  --label: #efe27b;
  --line: rgba(223, 236, 255, 0.12);
  --control-bg: rgba(20, 32, 52, 0.92);
  --control-text: #b4c6dc;
  --toc-bg: rgba(18, 30, 49, 0.92);
  --toc-active: rgba(103, 213, 255, 0.12);
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(circle at 14% 16%, rgba(97, 207, 255, 0.2), transparent 24%),
    radial-gradient(circle at 86% 12%, rgba(216, 255, 87, 0.12), transparent 18%),
    linear-gradient(140deg, var(--bg-start) 0%, var(--bg-mid) 48%, var(--bg-end) 100%);
  font-family: var(--sans);
  text-rendering: optimizeLegibility;
  transition: background 0.35s ease, color 0.35s ease;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.14) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.06) 1px, transparent 1px);
  background-size: 100% 40px, 40px 100%;
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.16), transparent 80%);
  opacity: 0.18;
}

a,
button {
  -webkit-tap-highlight-color: transparent;
}

a {
  color: inherit;
  text-decoration: none;
}

button {
  appearance: none;
}

.page-shell {
  position: relative;
  z-index: 1;
  width: min(calc(100% - 32px), var(--width));
  margin: 0 auto;
  padding: 24px 0 46px;
}

.site-header,
.doc-hero,
.toc-panel,
.doc-paper {
  animation: riseIn 0.78s ease both;
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}

.brand,
.control-panel,
.doc-hero,
.toc-panel,
.doc-paper {
  border: 1px solid var(--paper-border);
  background: var(--paper-soft);
  box-shadow: var(--paper-shadow);
  backdrop-filter: blur(14px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  padding: 12px 18px 12px 12px;
  border-radius: 999px;
}

.brand-badge {
  display: inline-grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--sky), var(--lime));
  color: #0e203d;
  font-size: 1rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  box-shadow: 0 14px 28px rgba(97, 207, 255, 0.2);
}

.brand-copy {
  display: grid;
  gap: 2px;
}

.brand-copy strong {
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.brand-copy small {
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.control-panel {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  justify-content: flex-end;
  padding: 10px;
  border-radius: 26px;
}

.control-group {
  display: grid;
  gap: 8px;
}

.control-label {
  padding-left: 10px;
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.segmented {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 8px;
  padding: 6px;
  border-radius: 999px;
  background: var(--control-bg);
}

.segmented a,
.theme-button {
  border: 0;
  background: transparent;
  color: var(--control-text);
  padding: 10px 15px;
  border-radius: 999px;
  font: inherit;
  font-size: 0.92rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.22s ease, background-color 0.22s ease, color 0.22s ease, box-shadow 0.22s ease;
}

.segmented a:hover,
.segmented a:focus-visible,
.theme-button:hover,
.theme-button:focus-visible {
  color: var(--ink);
  transform: translateY(-1px);
  outline: none;
}

.segmented .is-active,
.theme-button.is-active {
  background: var(--control-active);
  color: #10213d;
  box-shadow: 0 12px 24px rgba(97, 207, 255, 0.18);
}

.site-main {
  margin-top: 26px;
}

.doc-hero {
  display: grid;
  grid-template-columns: minmax(0, 1.16fr) minmax(250px, 0.84fr);
  gap: 24px;
  padding: clamp(24px, 4vw, 40px);
  border-radius: 34px;
  background:
    radial-gradient(circle at 16% 14%, rgba(255, 255, 255, 0.34), transparent 34%),
    linear-gradient(135deg, var(--paper), var(--paper-soft));
}

.hero-kicker,
.panel-kicker,
.meta-label,
.section-index {
  color: var(--label);
}

.hero-kicker,
.panel-kicker {
  margin: 0 0 10px;
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.doc-hero h1,
.section-head h2 {
  margin: 0;
}

.doc-hero h1 {
  font-family: var(--serif);
  font-size: clamp(2.4rem, 4vw, 4rem);
  line-height: 0.98;
  letter-spacing: -0.04em;
}

.hero-lead,
.meta-value,
.doc-intro,
.section-intro,
.doc-list li,
.site-footer p,
.footer-links a {
  color: var(--muted);
  line-height: 1.88;
}

.hero-lead {
  margin: 18px 0 0;
  font-size: 1.03rem;
}

.meta-grid {
  display: grid;
  gap: 12px;
  align-self: end;
}

.meta-card {
  padding: 18px 18px 16px;
  border-radius: 18px;
  border: 1px solid var(--paper-border);
  background: var(--paper);
  box-shadow: var(--paper-shadow-soft);
}

.meta-label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.meta-value {
  display: block;
  font-size: 1rem;
  font-weight: 700;
}

.doc-layout {
  display: grid;
  grid-template-columns: minmax(0, var(--toc-width)) minmax(0, 1fr);
  gap: 24px;
  margin-top: 24px;
  align-items: start;
}

.toc-panel {
  position: sticky;
  top: 84px;
  padding: 20px 18px;
  border-radius: 24px;
  background: var(--toc-bg);
}

.toc-links {
  display: grid;
  gap: 6px;
  margin-top: 14px;
}

.toc-links a {
  display: block;
  padding: 10px 12px;
  border-radius: 14px;
  color: var(--muted);
  font-size: 0.92rem;
  line-height: 1.45;
  transition: background-color 0.22s ease, color 0.22s ease, transform 0.22s ease;
}

.toc-links a:hover,
.toc-links a:focus-visible {
  color: var(--ink);
  background: var(--toc-active);
  transform: translateX(3px);
  outline: none;
}

.doc-paper {
  padding: clamp(24px, 4vw, 42px);
  border-radius: 30px;
  background: var(--paper);
}

.doc-intro {
  margin: 0;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--line);
  font-size: 1rem;
}

.doc-section {
  padding-top: 28px;
  border-top: 1px solid var(--line);
}

.doc-section + .doc-section {
  margin-top: 28px;
}

.section-head {
  display: flex;
  align-items: baseline;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 18px;
}

.section-index {
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.section-head h2 {
  font-family: var(--serif);
  font-size: clamp(1.48rem, 2.2vw, 2rem);
  line-height: 1.16;
  letter-spacing: -0.03em;
}

.section-intro {
  margin: 0 0 16px;
  font-size: 1rem;
}

.doc-list {
  margin: 0;
  padding-left: 1.4rem;
}

.doc-list > li {
  margin: 0 0 13px;
  color: var(--ink);
  font-size: 1rem;
}

.doc-list ul {
  margin-top: 10px;
  padding-left: 1.15rem;
  list-style: disc;
}

.site-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 22px;
  padding: 18px 2px 0;
}

.site-footer p {
  margin: 0;
  color: var(--muted);
  font-size: 0.94rem;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
}

.footer-links a {
  color: var(--muted);
  font-size: 0.94rem;
  font-weight: 700;
}

@keyframes riseIn {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 1040px) {
  .doc-hero,
  .doc-layout {
    grid-template-columns: 1fr;
  }

  .toc-panel {
    position: static;
  }
}

@media (max-width: 760px) {
  .page-shell {
    width: min(calc(100% - 20px), var(--width));
    padding-top: 16px;
  }

  .site-header,
  .site-footer {
    flex-direction: column;
    align-items: flex-start;
  }

  .control-panel {
    width: 100%;
    justify-content: flex-start;
  }

  .doc-hero,
  .toc-panel,
  .doc-paper {
    border-radius: 24px;
  }

  .doc-hero,
  .doc-paper {
    padding: 22px 18px;
  }
}

@media print {
  body { background: #fff; }
  body::before { display: none; }
  .page-shell { width: 100%; }
  .brand,
  .control-panel,
  .doc-hero,
  .toc-panel,
  .doc-paper {
    background: #fff;
    box-shadow: none;
    border: 1px solid #dddddd;
  }
}