/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body { min-height: 100vh; line-height: 1.6; -webkit-font-smoothing: antialiased; }
img, svg { display: block; max-width: 100%; }
ul, ol { list-style: none; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; border: none; background: none; cursor: pointer; }
:focus-visible { outline: 2px solid #1A5CFF; outline-offset: 2px; border-radius: 4px; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; } }

/* ===== CSS Variables ===== */
:root {
  --color-primary: #1A5CFF;
  --color-primary-hover: #0044DD;
  --color-accent: #FF6B35;
  --color-accent-hover: #E5551F;
  --color-bg: #F5F5F0;
  --color-surface: #FFFFFF;
  --color-dark-bg: #1B1B2F;
  --color-dark-surface: #232340;
  --color-neutral: #4A4A4A;
  --color-neutral-light: #6B6B6B;
  --color-highlight: #00D4AA;
  --color-border: #D1D1D1;
  --color-border-light: #E8E8E3;
  --color-text: #2C2C2C;
  --color-text-inverse: #F0F0F0;
  --color-shadow: rgba(26, 92, 255, 0.08);
  --color-shadow-hover: rgba(26, 92, 255, 0.16);
  --gradient-brand: linear-gradient(135deg, #1A5CFF, #FF6B35);
  --gradient-accent: linear-gradient(135deg, #FF6B35, #FF8F5E);
  --gradient-dark: linear-gradient(135deg, #1B1B2F, #2A2A45);
  --font-heading: 'Inter', 'PingFang SC', system-ui, -apple-system, sans-serif;
  --font-body: 'Inter', 'Noto Sans SC', system-ui, -apple-system, sans-serif;
  --font-data: 'JetBrains Mono', 'Fira Code', monospace;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 24px;
  --radius-xl: 32px;
  --radius-full: 9999px;
  --shadow-card: 0 2px 12px var(--color-shadow);
  --shadow-card-hover: 0 8px 28px var(--color-shadow-hover);
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2.5rem;
  --spacing-xl: 4rem;
  --container-max: 1200px;
  --header-height: 72px;
  --nav-top-offset: 1.5rem;
  --nav-right-offset: 2rem;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ===== Typography ===== */
body { font-family: var(--font-body); font-weight: 500; color: var(--color-text); background: var(--color-bg); font-size: 1rem; }
h1, h2, h3, h4, h5, h6 { font-family: var(--font-heading); font-weight: 700; font-style: italic; line-height: 1.2; }
h1 { font-size: clamp(2.25rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.75rem, 3.5vw, 2.5rem); }
h3 { font-size: clamp(1.25rem, 2.5vw, 1.75rem); }
h4 { font-size: 1.25rem; }
.data-value { font-family: var(--font-data); font-weight: 400; font-variant-numeric: tabular-nums; }
.caption { font-size: 0.75rem; color: var(--color-neutral-light); line-height: 1.4; }

/* ===== Skip Link ===== */
.skip-link { position: absolute; top: -100px; left: 1rem; background: var(--color-primary); color: #fff; padding: 0.75rem 1.5rem; border-radius: var(--radius-md); z-index: 10000; font-weight: 600; transition: top var(--transition); }
.skip-link:focus { top: 1rem; }

/* ===== Progress Bar ===== */
.progress-bar { position: fixed; top: 0; left: 0; width: 0; height: 3px; background: var(--gradient-brand); z-index: 9999; transition: width 0.1s linear; pointer-events: none; }

/* ===== Capsule Navigation ===== */
.capsule-nav { position: fixed; top: var(--nav-top-offset); right: var(--nav-right-offset); z-index: 9000; width: auto; max-width: calc(100vw - 2rem); }
.capsule-nav__inner { display: flex; align-items: center; gap: 0.5rem; background: rgba(255, 255, 255, 0.75); backdrop-filter: blur(18px) saturate(1.4); -webkit-backdrop-filter: blur(18px) saturate(1.4); border: 1px solid rgba(255, 255, 255, 0.3); border-radius: var(--radius-full); padding: 0.5rem 0.75rem 0.5rem 0.5rem; box-shadow: 0 4px 24px rgba(26, 92, 255, 0.10), 0 1px 4px rgba(0, 0, 0, 0.04); transition: box-shadow var(--transition); }
.capsule-nav__inner:hover { box-shadow: 0 8px 32px rgba(26, 92, 255, 0.16); }

.capsule-nav__brand { display: flex; align-items: center; gap: 0.4rem; padding: 0.3rem 0.8rem 0.3rem 0.3rem; border-radius: var(--radius-full); font-family: var(--font-heading); font-weight: 700; font-style: italic; font-size: 1rem; color: var(--color-primary); transition: background var(--transition); white-space: nowrap; }
.capsule-nav__brand:hover { background: rgba(26, 92, 255, 0.06); }
.capsule-nav__brand-icon { display: flex; align-items: center; color: var(--color-primary); }
.capsule-nav__brand-text { letter-spacing: 0.02em; }

.capsule-nav__toggle { display: none; flex-direction: column; justify-content: center; align-items: center; width: 40px; height: 40px; border-radius: 50%; background: transparent; transition: background var(--transition); }
.capsule-nav__toggle-bar { display: block; width: 20px; height: 2px; background: var(--color-neutral); border-radius: 2px; transition: all var(--transition); transform-origin: center; }
.capsule-nav__toggle-bar + .capsule-nav__toggle-bar { margin-top: 5px; }

.capsule-nav__menu { display: flex; align-items: center; }
.capsule-nav__list { display: flex; align-items: center; gap: 0.25rem; }
.capsule-nav__link { display: block; padding: 0.4rem 0.9rem; border-radius: var(--radius-full); font-size: 0.875rem; font-weight: 600; color: var(--color-neutral); transition: all var(--transition); white-space: nowrap; }
.capsule-nav__link:hover { background: rgba(26, 92, 255, 0.06); color: var(--color-primary); }
.capsule-nav__link[aria-current="page"] { background: var(--color-primary); color: #fff; box-shadow: 0 2px 8px rgba(26, 92, 255, 0.25); }

.capsule-nav__actions { display: flex; align-items: center; gap: 0.5rem; margin-left: 0.5rem; }

/* ===== Buttons ===== */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem; padding: 0.6rem 1.4rem; border-radius: var(--radius-md); font-family: var(--font-heading); font-weight: 700; font-style: italic; font-size: 0.875rem; transition: all var(--transition); white-space: nowrap; line-height: 1.2; }
.btn:active { transform: scale(0.97); }
.btn-primary { background: var(--color-primary); color: #fff; box-shadow: 0 2px 8px rgba(26, 92, 255, 0.2); }
.btn-primary:hover { background: var(--color-primary-hover); box-shadow: 0 4px 16px rgba(26, 92, 255, 0.3); transform: translateY(-1px); }
.btn-accent { background: var(--color-accent); color: #fff; box-shadow: 0 2px 8px rgba(255, 107, 53, 0.2); }
.btn-accent:hover { background: var(--color-accent-hover); box-shadow: 0 4px 16px rgba(255, 107, 53, 0.3); transform: translateY(-1px); }
.btn-capsule { border-radius: var(--radius-full); padding: 0.4rem 1.2rem; font-size: 0.8rem; font-style: normal; }

/* ===== Container ===== */
.container { max-width: var(--container-max); margin: 0 auto; padding: 0 var(--spacing-md); width: 100%; }

/* ===== Framed Hero (框景首屏) ===== */
.framed-hero { position: relative; background: var(--color-dark-bg); border-radius: var(--radius-lg); padding: 2.5rem; margin: 2rem 0; overflow: hidden; min-height: 320px; display: flex; align-items: center; justify-content: center; }
.framed-hero::before { content: ''; position: absolute; inset: 0; border: 2px solid rgba(26, 92, 255, 0.15); border-radius: var(--radius-lg); pointer-events: none; }
.framed-hero::after { content: ''; position: absolute; inset: 8px; border: 1px dashed rgba(255, 107, 53, 0.12); border-radius: calc(var(--radius-lg) - 4px); pointer-events: none; }
.framed-hero__scale { position: absolute; top: 12px; left: 12px; right: 12px; height: 4px; background: repeating-linear-gradient(90deg, rgba(26,92,255,0.25) 0px, rgba(26,92,255,0.25) 4px, transparent 4px, transparent 12px); border-radius: 2px; pointer-events: none; }
.framed-hero__scale--bottom { top: auto; bottom: 12px; }
.framed-hero__corner { position: absolute; width: 16px; height: 16px; border-color: var(--color-primary); border-style: solid; pointer-events: none; opacity: 0.5; }
.framed-hero__corner--tl { top: 12px; left: 12px; border-width: 2px 0 0 2px; border-radius: 4px 0 0 0; }
.framed-hero__corner--tr { top: 12px; right: 12px; border-width: 2px 2px 0 0; border-radius: 0 4px 0 0; }
.framed-hero__corner--bl { bottom: 12px; left: 12px; border-width: 0 0 2px 2px; border-radius: 0 0 0 4px; }
.framed-hero__corner--br { bottom: 12px; right: 12px; border-width: 0 2px 2px 0; border-radius: 0 0 4px 0; }
.framed-hero__content { position: relative; z-index: 1; width: 100%; }

/* ===== Chapter (编号章节) ===== */
.chapter { position: relative; padding: var(--spacing-lg) 0; }
.chapter__number { font-family: var(--font-heading); font-weight: 900; font-style: italic; font-size: clamp(3.5rem, 8vw, 6rem); line-height: 1; color: rgba(26, 92, 255, 0.08); user-select: none; position: absolute; top: 0; left: 0; pointer-events: none; }
.chapter__title { font-family: var(--font-heading); font-weight: 700; font-style: italic; font-size: clamp(1.5rem, 3vw, 2.25rem); color: var(--color-primary); margin-bottom: var(--spacing-sm); position: relative; z-index: 1; }
.chapter__body { position: relative; z-index: 1; margin-top: var(--spacing-sm); }

/* ===== Split Layout (左右分屏) ===== */
.split-layout { display: grid; grid-template-columns: 40% 60%; gap: var(--spacing-lg); align-items: start; }
.split-layout__panel { min-width: 0; }
.split-layout__panel--left { position: sticky; top: calc(var(--header-height) + 2rem); }
@media (max-width: 768px) {
  .split-layout { grid-template-columns: 1fr; gap: var(--spacing-md); }
  .split-layout__panel--left { position: static; }
}

/* ===== Card ===== */
.card { background: var(--color-surface); border-radius: var(--radius-md); padding: var(--spacing-md); box-shadow: var(--shadow-card); transition: all var(--transition); }
.card:hover { box-shadow: var(--shadow-card-hover); transform: translateY(-2px); }
.card--accent { border-left: 4px solid var(--color-accent); }
.card--data { border-top: 3px solid var(--color-primary); font-family: var(--font-data); }

/* ===== Breadcrumb ===== */
.breadcrumb { display: flex; flex-wrap: wrap; align-items: center; gap: 0.4rem; padding: var(--spacing-sm) 0; font-size: 0.8rem; color: var(--color-neutral-light); }
.breadcrumb a { color: var(--color-primary); transition: color var(--transition); }
.breadcrumb a:hover { color: var(--color-primary-hover); text-decoration: underline; }
.breadcrumb [aria-current="page"] { color: var(--color-neutral); font-weight: 600; }

/* ===== Section Divider ===== */
.section-divider { height: 2px; background: var(--gradient-brand); border-radius: 2px; margin: var(--spacing-lg) 0; opacity: 0.3; }

/* ===== Scroll Top ===== */
.scroll-top { position: fixed; bottom: 2rem; right: 2rem; width: 44px; height: 44px; border-radius: 50%; background: var(--gradient-brand); color: #fff; display: flex; align-items: center; justify-content: center; box-shadow: 0 4px 16px rgba(26, 92, 255, 0.25); z-index: 8000; opacity: 0; visibility: hidden; transform: translateY(12px); transition: all var(--transition); cursor: pointer; }
.scroll-top[data-visible] { opacity: 1; visibility: visible; transform: translateY(0); }
.scroll-top:hover { box-shadow: 0 6px 24px rgba(26, 92, 255, 0.35); transform: translateY(-2px); }
.scroll-top:active { transform: scale(0.92); }

/* ===== Footer ===== */
.site-footer { background: var(--color-dark-bg); color: var(--color-text-inverse); padding: var(--spacing-xl) 0 var(--spacing-lg); margin-top: var(--spacing-xl); }
.site-footer__columns { display: grid; grid-template-columns: 1.5fr 1fr 1fr 1fr; gap: var(--spacing-lg); margin-bottom: var(--spacing-lg); }
.site-footer__column--brand { grid-column: 1; }
.site-footer__brand { display: flex; align-items: center; gap: 0.5rem; font-family: var(--font-heading); font-weight: 700; font-style: italic; font-size: 1.3rem; color: var(--color-primary); margin-bottom: var(--spacing-xs); }
.site-footer__brand-icon { display: flex; align-items: center; color: var(--color-primary); }
.site-footer__tagline { font-size: 0.85rem; color: var(--color-highlight); margin-bottom: var(--spacing-sm); letter-spacing: 0.02em; }
.site-footer__trust { font-size: 0.75rem; color: var(--color-neutral-light); line-height: 1.5; max-width: 280px; }
.site-footer__column-title { font-family: var(--font-heading); font-weight: 700; font-style: italic; font-size: 0.9rem; color: var(--color-primary); margin-bottom: var(--spacing-sm); letter-spacing: 0.04em; text-transform: uppercase; }
.site-footer__links { display: flex; flex-direction: column; gap: 0.6rem; }
.site-footer__link { font-size: 0.85rem; color: rgba(240, 240, 240, 0.65); transition: all var(--transition); padding: 0.1rem 0; }
.site-footer__link:hover { color: var(--color-accent); padding-left: 4px; }
.site-footer__bottom { border-top: 1px solid rgba(255, 255, 255, 0.06); padding-top: var(--spacing-md); margin-top: var(--spacing-md); }
.site-footer__info { display: flex; flex-wrap: wrap; gap: var(--spacing-sm) var(--spacing-md); font-size: 0.75rem; color: rgba(240, 240, 240, 0.4); margin-bottom: var(--spacing-sm); }
.site-footer__contact-link { color: var(--color-primary); transition: color var(--transition); }
.site-footer__contact-link:hover { color: var(--color-accent); text-decoration: underline; }
.site-footer__disclaimer { font-size: 0.7rem; color: rgba(240, 240, 240, 0.3); margin-bottom: var(--spacing-xs); line-height: 1.5; }
.site-footer__copyright { font-size: 0.7rem; color: rgba(240, 240, 240, 0.25); }

/* ===== Responsive ===== */
@media (max-width: 900px) {
  .site-footer__columns { grid-template-columns: 1fr 1fr; gap: var(--spacing-md); }
  .site-footer__column--brand { grid-column: 1 / -1; }
}

@media (max-width: 768px) {
  :root { --nav-right-offset: 0.75rem; --nav-top-offset: 0.75rem; }
  .capsule-nav { right: var(--nav-right-offset); top: var(--nav-top-offset); width: auto; }
  .capsule-nav__inner { padding: 0.3rem 0.3rem 0.3rem 0.75rem; gap: 0.25rem; }
  .capsule-nav__brand-text { display: none; }
  .capsule-nav__actions { display: none; }
  .capsule-nav__toggle { display: flex; }
  .capsule-nav__menu { position: fixed; top: 0; left: 0; right: 0; bottom: 0; background: rgba(27, 27, 47, 0.97); backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px); border-radius: 0; flex-direction: column; justify-content: center; align-items: center; opacity: 0; visibility: hidden; transition: all var(--transition); pointer-events: none; }
  .capsule-nav__menu[data-open] { opacity: 1; visibility: visible; pointer-events: all; }
  .capsule-nav__list { flex-direction: column; gap: 0.75rem; text-align: center; }
  .capsule-nav__link { font-size: 1.3rem; padding: 0.6rem 1.6rem; color: rgba(240,240,240,0.7); }
  .capsule-nav__link:hover { color: #fff; background: rgba(255,255,255,0.06); }
  .capsule-nav__link[aria-current="page"] { background: var(--color-primary); color: #fff; }
  .capsule-nav__toggle[aria-expanded="true"] .capsule-nav__toggle-bar:nth-child(1) { transform: rotate(45deg) translate(3px, 3px); }
  .capsule-nav__toggle[aria-expanded="true"] .capsule-nav__toggle-bar:nth-child(2) { opacity: 0; transform: scaleX(0); }
  .capsule-nav__toggle[aria-expanded="true"] .capsule-nav__toggle-bar:nth-child(3) { transform: rotate(-45deg) translate(3px, -3px); }
  .framed-hero { padding: 1.5rem; min-height: 240px; border-radius: var(--radius-md); }
  .framed-hero__scale { display: none; }
  .framed-hero__corner { width: 12px; height: 12px; }
  .site-footer__columns { grid-template-columns: 1fr; gap: var(--spacing-md); }
  .site-footer__info { flex-direction: column; gap: 0.3rem; }
}

@media (max-width: 480px) {
  .capsule-nav__inner { padding: 0.25rem 0.25rem 0.25rem 0.5rem; }
  .capsule-nav__brand-icon svg { width: 24px; height: 24px; }
  .framed-hero { padding: 1rem; min-height: 180px; }
  .framed-hero__corner { display: none; }
}