/* ==========================================================================
   贝贝云 (Beibeiyun) - Luxury 经典建筑美学纯原生样式表
   零重型外部框架依赖 | 100% 原生 CSS | 秒开级性能 | 无障碍合规
   ========================================================================== */

/* --------------------------------------------------------------------------
   设计系统权威 Token 声明 (Luxury Design System)
   -------------------------------------------------------------------------- */
:root {
  /* 色彩与表面 (Color and surfaces) */
  --dp-color-ground: #f3eee4;           /* 温暖雪花石膏白 (Alabaster) */
  --dp-color-ground-2: #e4dbcc;         /* 灰褐过渡色 (Pale Taupe) */
  --dp-color-ink: #262321;              /* 炭黑主文本 (Charcoal Ink) */
  --dp-color-ink-2: #5f5750;            /* 次级辅助文本 (Supporting Text) */
  --dp-color-field: #262321;            /* 炭黑大区块背景 (Charcoal Field) */
  --dp-color-field-deep: #302c29;       /* 交互悬浮加深炭黑 */
  --dp-color-field-line: #46403a;       /* 炭黑背景上的细分割线 */
  --dp-color-on-field: #f3eee4;         /* 炭黑背景上的主文本色 */
  --dp-color-on-field-2: #c6bdb0;       /* 炭黑背景上的辅助文本色 */
  --dp-color-panel: #e4dbcc;            /* 浅灰褐面板色 (Taupe Panel) */
  --dp-color-panel-line: #c6b89f;       /* 面板分割细线 */
  --dp-color-accent: #b69355;           /* 雅致古董金 (Gold Spine & Accents) */
  --dp-color-accent-text: #76591f;      /* 浅底背景上的暗金色文字 */
  --dp-color-accent-light: #d2b071;     /* 炭黑背景上的亮金色文字 */
  --dp-color-rule: #d5cab8;             /* 浅底标准分割线 */

  /* 字体排印体系 (Typography) */
  --dp-typography-serif: "Luxury Garamond", "EB Garamond", Garamond, Georgia, "Songti SC", "SimSun", serif;
  --dp-typography-sans: "Luxury Sans", "Instrument Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --dp-typography-body: 1rem;
  --dp-typography-leading: 1.55;
  --dp-typography-serif-fallback: Georgia, "Times New Roman", serif;
  --dp-typography-label: 0.75rem;
  --dp-typography-label-tracking: 0.16em;
  --dp-typography-reading-small: 0.9375rem;
  --dp-typography-caption: 0.875rem;
  --dp-typography-attribution: 0.8125rem;
  --dp-typography-item-title: 1.375rem;
  --dp-typography-item-leading: 1.15;
  --dp-typography-item-tracking: -0.01em;

  /* 间距与网格尺度 (Spacing & Grid) */
  --dp-spacing-pad: 3rem;
  --dp-spacing-gap: 1.5rem;
  --dp-spacing-pad-mid: 2rem;
  --dp-spacing-pad-narrow: 1.25rem;
  --dp-spacing-gap-compact: 1rem;
  --dp-spacing-section-block: 6rem;
  --dp-spacing-section-roomy: 7rem;

  /* 控件与边框 (Controls & Borders) */
  --dp-radius-control: 0;                /* 恪守建筑美学：直角设计，拒绝圆角药丸 */
  --dp-border-focus-width: 2px;
  --dp-border-hairline: 1px;

  /* 动效 (Motion) */
  --dp-motion-interaction: 150ms;
  --dp-motion-door-content: 600ms;
  --dp-motion-door-delay: 450ms;
  --dp-motion-door-easing: cubic-bezier(0.2, 0.7, 0.2, 1);

  /* 全局容器最大宽度与页眉高度 */
  --content-max-width: 1240px;
  --header-height: 76px;
}

/* --------------------------------------------------------------------------
   全局重置与标准基础
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--dp-typography-sans);
  font-size: 16px;
  line-height: var(--dp-typography-leading);
  scroll-behavior: smooth;
  background-color: var(--dp-color-ground);
  color: var(--dp-color-ink);
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  position: relative;
  background-color: var(--dp-color-ground);
}

/* 键盘无障碍跳跃链接 */
.skip-link {
  position: absolute;
  top: -80px;
  left: 1.5rem;
  background: var(--dp-color-field);
  color: var(--dp-color-accent-light);
  border: 1px solid var(--dp-color-accent);
  padding: 0.85rem 1.5rem;
  z-index: 10000;
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  text-decoration: none;
  transition: top var(--dp-motion-interaction) ease;
}
.skip-link:focus {
  top: 1.5rem;
  outline: var(--dp-border-focus-width) solid var(--dp-color-accent);
  outline-offset: 4px;
}

/* 锚点滚动留白 (避免固定页眉遮挡) */
section[id], h2[id], h3[id], article[id] {
  scroll-margin-top: calc(var(--header-height) + 2rem);
}

/* --------------------------------------------------------------------------
   顶部页眉与导航系统 (Header & Navigation)
   -------------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 999;
  height: var(--header-height);
  background-color: rgba(243, 238, 228, 0.94);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: var(--dp-border-hairline) solid var(--dp-color-rule);
  transition: background-color var(--dp-motion-interaction) ease;
}

.header-container {
  max-width: var(--content-max-width);
  height: 100%;
  margin: 0 auto;
  padding: 0 var(--dp-spacing-pad);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--dp-spacing-gap);
}

.brand-wrap {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--dp-color-ink);
}

.brand-mark {
  display: inline-block;
  width: 28px;
  height: 28px;
  border: 1px solid var(--dp-color-accent);
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--dp-typography-serif);
  font-size: 0.9rem;
  color: var(--dp-color-accent-text);
  font-style: italic;
  font-weight: bold;
}

.brand-text {
  font-family: var(--dp-typography-serif);
  font-size: 1.45rem;
  font-weight: 500;
  letter-spacing: -0.02em;
  color: var(--dp-color-ink);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 2rem;
}

.nav-link {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  color: var(--dp-color-ink-2);
  text-decoration: none;
  position: relative;
  padding: 0.5rem 0;
  transition: color var(--dp-motion-interaction) ease;
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--dp-color-ink);
}

.nav-link::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0%;
  height: 1px;
  background-color: var(--dp-color-accent);
  transition: width var(--dp-motion-interaction) ease;
}

.nav-link:hover::after,
.nav-link:focus-visible::after,
.nav-link.active::after {
  width: 100%;
}

.nav-tag {
  display: inline-block;
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  padding: 1px 5px;
  margin-left: 4px;
  border: 1px solid var(--dp-color-accent);
  color: var(--dp-color-accent-text);
  vertical-align: middle;
}

/* 按钮通用样式 (Buttons) */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 3rem; /* 48px 满足无障碍触控目标 */
  padding: 0 1.75rem;
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  font-weight: 600;
  border-radius: var(--dp-radius-control);
  text-decoration: none;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color var(--dp-motion-interaction) ease,
              color var(--dp-motion-interaction) ease,
              border-color var(--dp-motion-interaction) ease,
              transform var(--dp-motion-interaction) ease;
}

.btn:active {
  transform: translateY(1px);
}

.btn:focus-visible {
  outline: var(--dp-border-focus-width) solid var(--dp-color-accent);
  outline-offset: 3px;
}

.btn-primary {
  background-color: var(--dp-color-field);
  color: var(--dp-color-on-field);
  border-color: var(--dp-color-field);
}

.btn-primary:hover {
  background-color: var(--dp-color-field-deep);
  border-color: var(--dp-color-accent);
  color: var(--dp-color-accent-light);
}

.btn-secondary {
  background-color: transparent;
  color: var(--dp-color-ink);
  border-color: var(--dp-color-ink-2);
}

.btn-secondary:hover {
  border-color: var(--dp-color-accent);
  color: var(--dp-color-accent-text);
  background-color: rgba(182, 147, 85, 0.06);
}

.btn-on-charcoal {
  background-color: var(--dp-color-ground);
  color: var(--dp-color-field);
  border-color: var(--dp-color-ground);
}

.btn-on-charcoal:hover {
  background-color: var(--dp-color-accent-light);
  color: var(--dp-color-field);
  border-color: var(--dp-color-accent);
}

/* --------------------------------------------------------------------------
   建筑网格与金色中轴线 (Twelve-Column Grid & Gold Spine)
   -------------------------------------------------------------------------- */
.luxury-container {
  max-width: var(--content-max-width);
  margin: 0 auto;
  padding: 0 var(--dp-spacing-pad);
  position: relative;
}

/* 核心布局网格：12 列体系 */
.luxury-grid {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--dp-spacing-gap);
  position: relative;
}

/* 金色脊柱竖线 (Gold Spine)：置于前两列边缘 */
.spine-wrapper {
  position: relative;
}

.spine-wrapper::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: calc(var(--dp-spacing-pad) + ( (100% - var(--dp-spacing-pad) * 2 - var(--dp-spacing-gap) * 11) / 12 * 2 + var(--dp-spacing-gap) ));
  width: 1px;
  background-color: var(--dp-color-accent);
  opacity: 0.55;
  pointer-events: none;
  z-index: 10;
}

/* 罗马数字标头 (Roman Numerals) */
.numeral-tag {
  font-family: var(--dp-typography-serif);
  font-size: 1.15rem;
  letter-spacing: 0.12em;
  color: var(--dp-color-accent-text);
  font-style: italic;
  display: block;
  margin-bottom: 0.75rem;
}

.on-field .numeral-tag {
  color: var(--dp-color-accent-light);
}

/* --------------------------------------------------------------------------
   区段基调系统 (Tonal Surfaces)
   -------------------------------------------------------------------------- */
.surface-ground {
  background-color: var(--dp-color-ground);
  color: var(--dp-color-ink);
  padding: var(--dp-spacing-section-block) 0;
}

.surface-panel {
  background-color: var(--dp-color-panel);
  color: var(--dp-color-ink);
  padding: var(--dp-spacing-section-block) 0;
  border-top: var(--dp-border-hairline) solid var(--dp-color-panel-line);
  border-bottom: var(--dp-border-hairline) solid var(--dp-color-panel-line);
}

.surface-field {
  background-color: var(--dp-color-field);
  color: var(--dp-color-on-field);
  padding: var(--dp-spacing-section-roomy) 0;
}

/* --------------------------------------------------------------------------
   主视觉区 (Hero Section - Numeral I)
   -------------------------------------------------------------------------- */
.hero-section {
  padding-top: 5rem;
  padding-bottom: 6rem;
  position: relative;
}

.hero-content {
  grid-column: 3 / 8;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.hero-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.hero-status {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  color: var(--dp-color-accent-text);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.hero-status-dot {
  width: 6px;
  height: 6px;
  background-color: var(--dp-color-accent);
  display: inline-block;
}

.hero-title {
  font-family: var(--dp-typography-serif);
  font-size: clamp(2.75rem, 5.5vw, 4.5rem);
  line-height: 1.05;
  font-weight: 400;
  letter-spacing: -0.02em;
  color: var(--dp-color-ink);
  margin-bottom: 1.5rem;
}

.hero-title em {
  font-style: italic;
  color: var(--dp-color-accent-text);
}

.hero-subtitle {
  font-family: var(--dp-typography-serif);
  font-size: 1.45rem;
  line-height: 1.4;
  color: var(--dp-color-ink);
  margin-bottom: 1.25rem;
  font-weight: 400;
}

.hero-desc {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  line-height: 1.65;
  color: var(--dp-color-ink-2);
  margin-bottom: 2.5rem;
  max-width: 36em;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  flex-wrap: wrap;
}

.hero-visual {
  grid-column: 9 / 13;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.hero-portrait-card {
  border: 1px solid var(--dp-color-accent);
  padding: 1.75rem;
  background-color: #f8f4ec;
  position: relative;
  box-shadow: 0 1px 2px rgba(0,0,0,0.03);
}

.hero-stat-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 1rem 0;
  border-bottom: 1px solid var(--dp-color-rule);
}

.hero-stat-row:last-child {
  border-bottom: none;
}

.hero-stat-val {
  font-family: var(--dp-typography-serif);
  font-size: 2.25rem;
  font-weight: 400;
  color: var(--dp-color-ink);
}

.hero-stat-label {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  color: var(--dp-color-ink-2);
}

/* --------------------------------------------------------------------------
   产品核心优势卡片 (Core Advantages - Numeral II)
   -------------------------------------------------------------------------- */
.section-header-wrap {
  grid-column: 3 / 13;
  margin-bottom: 3.5rem;
}

.section-head-title {
  font-family: var(--dp-typography-serif);
  font-size: clamp(2rem, 3.5vw, 2.75rem);
  font-weight: 400;
  line-height: 1.15;
  color: var(--dp-color-ink);
  margin-bottom: 0.75rem;
}

.section-head-desc {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-body);
  color: var(--dp-color-ink-2);
  max-width: 42em;
}

.advantages-grid {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--dp-spacing-gap);
}

.advantage-card {
  background-color: var(--dp-color-ground);
  border: 1px solid var(--dp-color-panel-line);
  padding: 2.25rem 1.75rem;
  display: flex;
  flex-direction: column;
  transition: border-color var(--dp-motion-interaction) ease;
}

.advantage-card:hover {
  border-color: var(--dp-color-accent);
}

.advantage-num {
  font-family: var(--dp-typography-serif);
  font-size: 1.5rem;
  color: var(--dp-color-accent-text);
  font-style: italic;
  margin-bottom: 1.5rem;
  display: block;
}

.advantage-icon-box {
  width: 48px;
  height: 48px;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--dp-color-rule);
  color: var(--dp-color-accent-text);
}

.advantage-card h3 {
  font-family: var(--dp-typography-serif);
  font-size: var(--dp-typography-item-title);
  line-height: var(--dp-typography-item-leading);
  margin-bottom: 1rem;
  color: var(--dp-color-ink);
}

.advantage-card p {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  line-height: 1.6;
  color: var(--dp-color-ink-2);
}

/* --------------------------------------------------------------------------
   流媒体与 AI 支持图卡 (Streaming & AI Support - Numeral III)
   -------------------------------------------------------------------------- */
.support-duo {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--dp-spacing-gap);
}

.support-card {
  background-color: #fbf8f2;
  border: 1px solid var(--dp-color-rule);
  padding: 2.5rem 2rem;
  display: flex;
  flex-direction: column;
}

.support-card h3 {
  font-family: var(--dp-typography-serif);
  font-size: 1.75rem;
  line-height: 1.2;
  margin-bottom: 1rem;
  color: var(--dp-color-ink);
}

.support-card p {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  line-height: 1.6;
  color: var(--dp-color-ink-2);
  margin-bottom: 2rem;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin-top: auto;
}

.tag-item {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  border: 1px solid var(--dp-color-rule);
  padding: 0.4rem 0.85rem;
  color: var(--dp-color-ink);
  background-color: var(--dp-color-ground);
}

/* --------------------------------------------------------------------------
   套餐价格对比表 (Pricing Comparison - Numeral IV)
   -------------------------------------------------------------------------- */
.pricing-section {
  position: relative;
}

.pricing-grid {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--dp-spacing-gap);
  align-items: stretch;
}

.pricing-card {
  background-color: #ffffff;
  border: 1px solid var(--dp-color-rule);
  padding: 2.75rem 2rem;
  display: flex;
  flex-direction: column;
  position: relative;
}

/* 核心推荐列：炭黑专属特色背景 (Charcoal Featured Column) */
.pricing-card.featured {
  background-color: var(--dp-color-field);
  color: var(--dp-color-on-field);
  border: 1px solid var(--dp-color-accent);
  box-shadow: 0 4px 20px rgba(0,0,0,0.12);
}

.featured-spine-flag {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background-color: var(--dp-color-accent);
}

.pricing-tier-name {
  font-family: var(--dp-typography-serif);
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

.pricing-tier-desc {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-caption);
  color: var(--dp-color-ink-2);
  margin-bottom: 1.75rem;
}

.pricing-card.featured .pricing-tier-desc {
  color: var(--dp-color-on-field-2);
}

.pricing-price-wrap {
  display: flex;
  align-items: baseline;
  gap: 0.35rem;
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--dp-color-rule);
}

.pricing-card.featured .pricing-price-wrap {
  border-bottom-color: var(--dp-color-field-line);
}

.pricing-currency {
  font-family: var(--dp-typography-serif);
  font-size: 1.5rem;
  color: var(--dp-color-accent-text);
}

.pricing-card.featured .pricing-currency {
  color: var(--dp-color-accent-light);
}

.pricing-amount {
  font-family: var(--dp-typography-serif);
  font-size: 3.25rem;
  font-weight: 400;
  line-height: 1;
}

.pricing-cycle {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-caption);
  color: var(--dp-color-ink-2);
}

.pricing-card.featured .pricing-cycle {
  color: var(--dp-color-on-field-2);
}

.pricing-features-list {
  list-style: none;
  margin-bottom: 2.5rem;
  flex-grow: 1;
}

.pricing-feature-item {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  padding: 0.65rem 0;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  border-bottom: 1px dashed var(--dp-color-rule);
}

.pricing-card.featured .pricing-feature-item {
  border-bottom-color: var(--dp-color-field-line);
}

.pricing-feature-item:last-child {
  border-bottom: none;
}

.pricing-feature-mark {
  color: var(--dp-color-accent-text);
  font-weight: bold;
}

.pricing-card.featured .pricing-feature-mark {
  color: var(--dp-color-accent-light);
}

/* --------------------------------------------------------------------------
   用户评价 (User Reviews - Numeral V)
   -------------------------------------------------------------------------- */
.reviews-grid {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--dp-spacing-gap);
}

.review-card {
  background-color: #ffffff;
  border: 1px solid var(--dp-color-rule);
  padding: 2rem 1.75rem;
  display: flex;
  flex-direction: column;
}

.review-stars {
  color: var(--dp-color-accent);
  letter-spacing: 0.2em;
  margin-bottom: 1rem;
  font-size: 0.9rem;
}

.review-quote {
  font-family: var(--dp-typography-serif);
  font-size: 1.15rem;
  line-height: 1.5;
  font-style: italic;
  color: var(--dp-color-ink);
  margin-bottom: 1.75rem;
  flex-grow: 1;
}

.review-author {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding-top: 1rem;
  border-top: 1px solid var(--dp-color-rule);
}

.review-avatar {
  width: 38px;
  height: 38px;
  background-color: var(--dp-color-ground-2);
  border: 1px solid var(--dp-color-accent);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--dp-typography-serif);
  font-weight: bold;
  font-size: 1rem;
  color: var(--dp-color-accent-text);
}

.review-info h4 {
  font-family: var(--dp-typography-sans);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--dp-color-ink);
}

.review-info p {
  font-family: var(--dp-typography-sans);
  font-size: 0.75rem;
  color: var(--dp-color-ink-2);
}

/* --------------------------------------------------------------------------
   常见问题解答 (FAQ Disclosures - Numeral VI)
   -------------------------------------------------------------------------- */
.faq-wrap {
  grid-column: 3 / 13;
}

.faq-list {
  display: flex;
  flex-direction: column;
  border-top: 1px solid var(--dp-color-rule);
}

.faq-item {
  border-bottom: 1px solid var(--dp-color-rule);
  transition: background-color var(--dp-motion-interaction) ease;
}

.faq-item[open] {
  background-color: rgba(228, 219, 204, 0.25);
}

.faq-summary {
  list-style: none;
  padding: 1.5rem 0.5rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--dp-typography-serif);
  font-size: 1.35rem;
  color: var(--dp-color-ink);
  font-weight: 400;
  user-select: none;
}

.faq-summary::-webkit-details-marker {
  display: none;
}

.faq-summary:focus-visible {
  outline: var(--dp-border-focus-width) solid var(--dp-color-accent);
  outline-offset: 2px;
}

.faq-icon-indicator {
  font-family: var(--dp-typography-serif);
  font-size: 1.4rem;
  color: var(--dp-color-accent-text);
  margin-left: 1rem;
  display: inline-block;
  transition: transform var(--dp-motion-interaction) ease;
}

.faq-item[open] .faq-icon-indicator {
  transform: rotate(45deg);
}

.faq-body {
  padding: 0 0.5rem 1.75rem 0.5rem;
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  line-height: 1.7;
  color: var(--dp-color-ink-2);
}

.faq-body a {
  color: var(--dp-color-accent-text);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* --------------------------------------------------------------------------
   炭黑收尾呼吁区 (Charcoal Callout Field)
   -------------------------------------------------------------------------- */
.closing-field {
  background-color: var(--dp-color-field);
  color: var(--dp-color-on-field);
  padding: 6rem 0;
  border-top: 1px solid var(--dp-color-accent);
}

.closing-grid {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: var(--dp-spacing-gap);
  align-items: center;
}

.closing-title {
  font-family: var(--dp-typography-serif);
  font-size: clamp(2.25rem, 4.5vw, 3.5rem);
  font-weight: 400;
  line-height: 1.1;
  color: var(--dp-color-on-field);
  margin-bottom: 1.25rem;
}

.closing-desc {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-reading-small);
  line-height: 1.65;
  color: var(--dp-color-on-field-2);
  margin-bottom: 2rem;
  max-width: 32em;
}

.closing-actions {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

/* --------------------------------------------------------------------------
   页脚规范 (Footer - 只保留4个链接，打开新页面)
   -------------------------------------------------------------------------- */
.site-footer {
  background-color: var(--dp-color-field);
  color: var(--dp-color-on-field-2);
  border-top: 1px solid var(--dp-color-field-line);
  padding: 4rem 0 3rem 0;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

.footer-nav-bar {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 3.5rem;
  flex-wrap: wrap;
  padding-bottom: 2.5rem;
  border-bottom: 1px solid var(--dp-color-field-line);
}

.footer-title-link {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  font-weight: 600;
  color: var(--dp-color-on-field);
  text-decoration: none;
  position: relative;
  padding: 0.5rem 0;
  transition: color var(--dp-motion-interaction) ease;
}

.footer-title-link:hover,
.footer-title-link:focus-visible {
  color: var(--dp-color-accent-light);
}

.footer-title-link::after {
  content: " ↗";
  font-size: 0.85em;
  color: var(--dp-color-accent-light);
}

.footer-bottom-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-caption);
  color: var(--dp-color-on-field-2);
  flex-wrap: wrap;
  gap: 1rem;
}

.footer-brand {
  font-family: var(--dp-typography-serif);
  font-size: 1.1rem;
  color: var(--dp-color-on-field);
}

/* --------------------------------------------------------------------------
   知识科普专栏与单篇文章排版 (Article & Knowledge Specific)
   -------------------------------------------------------------------------- */
.article-header {
  padding: 4rem 0 3rem 0;
  border-bottom: 1px solid var(--dp-color-rule);
  margin-bottom: 3rem;
}

.article-header h1 {
  font-family: var(--dp-typography-serif);
  font-size: clamp(2rem, 3.5vw, 2.75rem);
  line-height: 1.2;
  font-weight: 400;
  color: var(--dp-color-ink);
  margin-bottom: 1.25rem;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-caption);
  color: var(--dp-color-ink-2);
  flex-wrap: wrap;
}

.article-body-content {
  grid-column: 3 / 11;
  font-family: var(--dp-typography-sans);
  font-size: 1.05rem;
  line-height: 1.8;
  color: var(--dp-color-ink);
}

.article-body-content h2 {
  font-family: var(--dp-typography-serif);
  font-size: 1.85rem;
  font-weight: 400;
  margin: 2.5rem 0 1rem 0;
  color: var(--dp-color-ink);
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--dp-color-rule);
}

.article-body-content h3 {
  font-family: var(--dp-typography-serif);
  font-size: 1.35rem;
  font-weight: 500;
  margin: 1.75rem 0 0.75rem 0;
  color: var(--dp-color-ink);
}

.article-body-content p {
  margin-bottom: 1.5rem;
  color: #383431;
}

.article-body-content ul,
.article-body-content ol {
  margin: 0 0 1.5rem 1.5rem;
  color: #383431;
}

.article-body-content li {
  margin-bottom: 0.5rem;
}

.article-body-content a {
  color: var(--dp-color-accent-text);
  font-weight: 600;
  text-decoration: underline;
  text-underline-offset: 3px;
}

.article-highlight-box {
  background-color: var(--dp-color-panel);
  border-left: 3px solid var(--dp-color-accent);
  padding: 1.5rem;
  margin: 2rem 0;
}

.article-highlight-box p:last-child {
  margin-bottom: 0;
}

.article-faq-section {
  margin-top: 4rem;
  padding-top: 2.5rem;
  border-top: 2px solid var(--dp-color-accent);
}

.article-faq-section h2 {
  font-family: var(--dp-typography-serif);
  font-size: 1.75rem;
  margin-bottom: 1.5rem;
}

.article-nav-foot {
  margin-top: 3.5rem;
  padding-top: 2rem;
  border-top: 1px solid var(--dp-color-rule);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

/* 知识科普目录卡片 (Knowledge Index Grid) */
.knowledge-grid {
  grid-column: 3 / 13;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--dp-spacing-gap);
}

.knowledge-card {
  background-color: #ffffff;
  border: 1px solid var(--dp-color-rule);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  transition: border-color var(--dp-motion-interaction) ease,
              transform var(--dp-motion-interaction) ease;
}

.knowledge-card:hover {
  border-color: var(--dp-color-accent);
  transform: translateY(-2px);
}

.knowledge-card-tag {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-label);
  letter-spacing: var(--dp-typography-label-tracking);
  text-transform: uppercase;
  color: var(--dp-color-accent-text);
  margin-bottom: 0.75rem;
  display: block;
}

.knowledge-card h3 {
  font-family: var(--dp-typography-serif);
  font-size: 1.35rem;
  line-height: 1.3;
  margin-bottom: 1rem;
  color: var(--dp-color-ink);
}

.knowledge-card p {
  font-family: var(--dp-typography-sans);
  font-size: var(--dp-typography-caption);
  line-height: 1.6;
  color: var(--dp-color-ink-2);
  margin-bottom: 1.5rem;
  flex-grow: 1;
}

.knowledge-card-foot {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--dp-typography-sans);
  font-size: 0.75rem;
  color: var(--dp-color-accent-text);
  font-weight: 600;
  padding-top: 0.75rem;
  border-top: 1px solid var(--dp-color-ground-2);
}

/* 网站地图列表卡片 (Sitemap Page) */
.sitemap-group {
  grid-column: 3 / 13;
  margin-bottom: 3rem;
}

.sitemap-group h2 {
  font-family: var(--dp-typography-serif);
  font-size: 1.75rem;
  margin-bottom: 1.25rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--dp-color-rule);
}

.sitemap-links-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.sitemap-link-card {
  padding: 1rem 1.25rem;
  background-color: #ffffff;
  border: 1px solid var(--dp-color-rule);
  text-decoration: none;
  color: var(--dp-color-ink);
  transition: border-color var(--dp-motion-interaction) ease;
}

.sitemap-link-card:hover {
  border-color: var(--dp-color-accent);
}

.sitemap-link-card strong {
  display: block;
  font-family: var(--dp-typography-serif);
  font-size: 1.05rem;
  margin-bottom: 0.25rem;
}

.sitemap-link-card span {
  font-size: 0.75rem;
  color: var(--dp-color-ink-2);
}

/* --------------------------------------------------------------------------
   响应式媒体查询 (Responsive Breakpoints: 1100px, 720px, 480px)
   -------------------------------------------------------------------------- */

/* 中屏适配 (721px - 1100px) */
@media (max-width: 1100px) {
  :root {
    --dp-spacing-pad: var(--dp-spacing-pad-mid);
    --dp-spacing-gap: var(--dp-spacing-gap-compact);
  }

  .spine-wrapper::before {
    left: calc(var(--dp-spacing-pad) + 40px);
  }

  .hero-content {
    grid-column: 3 / 8;
  }
  .hero-visual {
    grid-column: 8 / 13;
  }

  .advantages-grid,
  .pricing-grid,
  .reviews-grid,
  .knowledge-grid,
  .sitemap-links-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .article-body-content {
    grid-column: 3 / 13;
  }
}

/* 窄屏与手机端完美单栏适配 (<= 720px) */
@media (max-width: 720px) {
  :root {
    --dp-spacing-pad: var(--dp-spacing-pad-narrow);
    --header-height: 64px;
    --dp-spacing-section-block: 4rem;
    --dp-spacing-section-roomy: 4.5rem;
  }

  /* 移动端金色脊柱线靠最左侧边缘 */
  .spine-wrapper::before {
    left: 1.25rem;
    opacity: 0.35;
  }

  .header-container {
    padding: 0 var(--dp-spacing-pad);
  }

  .main-nav {
    display: none; /* 简化移动端，保留主 CTA */
  }

  /* 12 列在手机端转为全宽单栏堆叠 */
  .luxury-grid {
    display: flex;
    flex-direction: column;
    gap: 2rem;
  }

  .hero-section {
    padding-top: 2.5rem;
    padding-bottom: 3.5rem;
  }

  .hero-content,
  .hero-visual,
  .section-header-wrap,
  .advantages-grid,
  .support-duo,
  .pricing-grid,
  .reviews-grid,
  .faq-wrap,
  .closing-grid,
  .article-body-content,
  .knowledge-grid,
  .sitemap-group {
    grid-column: 1 / -1;
    width: 100%;
  }

  .hero-title {
    font-size: 2.35rem;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .advantages-grid,
  .support-duo,
  .pricing-grid,
  .reviews-grid,
  .knowledge-grid,
  .sitemap-links-grid {
    grid-template-columns: 1fr;
  }

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

  .closing-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .closing-actions .btn {
    width: 100%;
  }

  .footer-nav-bar {
    gap: 1.5rem;
    flex-direction: column;
    align-items: center;
  }

  .footer-bottom-row {
    flex-direction: column;
    text-align: center;
    gap: 0.75rem;
  }
}

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