/* ============================================================
   DL - 开放即时通讯协议  |  蓝白亮色设计系统
   ============================================================ */

/* ----- CSS 自定义属性（设计令牌）----- */
:root {
  /* 背景色阶 — 蓝白亮色 */
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-deep: #f1f5f9;
  --color-elevated: #ffffff;

  /* 主色 — 蓝色系 */
  --color-primary: #3b82f6;
  --color-primary-bright: #60a5fa;
  --color-primary-dark: #2563eb;
  --color-primary-light: #93c5fd;
  --color-primary-glow: rgba(59, 130, 246, 0.12);
  --color-primary-soft: #eff6ff;

  /* 强调色 — 青色 */
  --color-accent: #06b6d4;
  --color-accent-glow: rgba(6, 182, 212, 0.12);
  --color-accent-soft: #ecfeff;

  /* 暖色点缀 */
  --color-violet: #8b5cf6;
  --color-violet-glow: rgba(139, 92, 246, 0.10);

  /* 文字 */
  --color-text: #0f172a;
  --color-text-secondary: #475569;
  --color-text-muted: #94a3b8;

  /* 边框 */
  --color-border: #e2e8f0;
  --color-border-hover: #93c5fd;
  --color-border-subtle: #f1f5f9;

  /* 面板 */
  --color-panel-bg: #ffffff;
  --color-panel-border: #e2e8f0;

  /* 字体 */
  --font-sans: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;
  --font-display: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;

  /* 圆角 */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.25rem;
  --radius-2xl: 1.5rem;

  /* 阴影 */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 1px 3px rgba(0, 0, 0, 0.06), 0 4px 12px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.06), 0 8px 32px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 0 3px rgba(59, 130, 246, 0.10);
  --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.04), 0 4px 16px rgba(0, 0, 0, 0.04);

  /* 过渡 */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 400ms ease;

  /* 代码块 */
  --color-code-bg: #1e293b;
  --color-code-border: #334155;
}

/* ----- 全局重置 ----- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text-secondary);
  background-color: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* main 撑满剩余空间，消除底部留空 */
main {
  flex: 1;
  position: relative;
  z-index: 1;
}

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

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

ul {
  list-style: none;
}

/* ----- 排版 ----- */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text);
  font-family: var(--font-display);
  line-height: 1.25;
}

.font-display {
  font-family: var(--font-display);
}

.text-gradient {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ----- 背景效果（亮色版 — 极简光晕）----- */
.cosmic-bg {
  position: fixed;
  inset: 0;
  z-index: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 0%, rgba(59, 130, 246, 0.05) 0%, transparent 60%),
    radial-gradient(ellipse 60% 40% at 85% 50%, rgba(6, 182, 212, 0.03) 0%, transparent 55%),
    radial-gradient(ellipse 45% 35% at 15% 70%, rgba(139, 92, 246, 0.03) 0%, transparent 50%),
    var(--color-bg);
  pointer-events: none;
}

/* 细微的网格纹理 */
.cosmic-bg::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(59, 130, 246, 0.04) 1px, transparent 1px);
  background-size: 48px 48px;
  opacity: 0.6;
}

.orbit-rings {
  display: none;
}

.ambient-glow {
  position: fixed;
  border-radius: 50%;
  filter: blur(140px);
  pointer-events: none;
  z-index: 0;
  opacity: 0.5;
}

.glow-blue {
  width: 600px;
  height: 400px;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.12), transparent 70%);
  top: -10%;
  left: 50%;
  transform: translateX(-50%);
}

.glow-cyan {
  width: 450px;
  height: 320px;
  background: radial-gradient(circle, rgba(6, 182, 212, 0.08), transparent 70%);
  bottom: 20%;
  right: 8%;
}

.glow-violet {
  width: 380px;
  height: 300px;
  background: radial-gradient(circle, rgba(139, 92, 246, 0.06), transparent 70%);
  bottom: 30%;
  left: 5%;
}

/* ----- 布局容器 ----- */
.container {
  width: 100%;
  max-width: 1280px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 1rem;
  padding-right: 1rem;
}

@media (min-width: 640px) {
  .container { padding-left: 1.5rem; padding-right: 1.5rem; }
}

@media (min-width: 1024px) {
  .container { padding-left: 2rem; padding-right: 2rem; }
}

.section {
  padding: 4rem 1rem;
}

@media (min-width: 768px) {
  .section { padding: 5.5rem 1rem; }
}

.section-header {
  text-align: center;
  margin-bottom: 3rem;
}

.section-label {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  color: var(--color-primary);
  text-transform: uppercase;
  margin-bottom: 0.75rem;
  padding: 0.3rem 0.9rem;
  background: var(--color-primary-soft);
  border: 1px solid rgba(59, 130, 246, 0.12);
  border-radius: 9999px;
}

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  font-family: var(--font-display);
  margin-bottom: 1rem;
}

@media (min-width: 768px) {
  .section-title { font-size: 2.25rem; }
}

.divider {
  width: 6rem;
  height: 3px;
  margin: 0 auto 1.25rem;
  border-radius: 2px;
  background: linear-gradient(90deg, transparent, var(--color-primary), var(--color-accent), transparent);
}

.section-desc {
  color: var(--color-text-secondary);
  max-width: 36rem;
  margin: 0 auto;
  font-size: 1.05rem;
  line-height: 1.7;
}

/* ----- 头部导航（白色毛玻璃）----- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 4rem;
}

@media (min-width: 768px) {
  .header-inner { height: 5rem; }
}

/* Logo */
.logo-link {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  position: relative;
  z-index: 2;
}

.logo-img-wrap {
  position: relative;
  width: 2.25rem;
  height: 2.25rem;
}

@media (min-width: 768px) {
  .logo-img-wrap { width: 2.5rem; height: 2.5rem; }
}

.logo-img-wrap img {
  width: 100%;
  height: 100%;
  border-radius: var(--radius-md);
  object-fit: cover;
}

.logo-ring {
  position: absolute;
  inset: 0;
  border-radius: var(--radius-md);
  border: 1px solid rgba(59, 130, 246, 0.25);
  transition: border-color var(--transition-normal);
}

.logo-link:hover .logo-ring {
  border-color: rgba(59, 130, 246, 0.55);
}

.logo-text {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: 0.15em;
  font-family: var(--font-display);
}

@media (min-width: 768px) {
  .logo-text { font-size: 1.6rem; }
}

/* 桌面导航 */
.nav-desktop {
  display: none;
}

@media (min-width: 768px) {
  .nav-desktop {
    display: flex;
    align-items: center;
    gap: 0.25rem;
  }
}

.nav-link {
  padding: 0.5rem 1rem;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  letter-spacing: 0.025em;
  border-radius: var(--radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-primary);
  background: var(--color-primary-soft);
}

.nav-link-accent {
  color: var(--color-primary);
  font-weight: 600;
}

/* 桌面 CTA 按钮 */
.header-cta {
  display: none;
}

@media (min-width: 768px) {
  .header-cta { display: block; }
}

/* 移动端菜单复选框（隐藏） */
.menu-toggle-checkbox {
  display: none;
}

/* 移动端菜单按钮（label 伪装） */
.mobile-menu-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.5rem;
  color: var(--color-text-secondary);
  background: none;
  border: none;
  cursor: pointer;
  transition: color var(--transition-fast);
  position: relative;
  z-index: 2;
}

.mobile-menu-btn:hover {
  color: var(--color-primary);
}

.mobile-menu-btn svg {
  width: 1.5rem;
  height: 1.5rem;
}

/* 图标切换：默认显示汉堡，选中后显示 X */
.menu-toggle-checkbox:checked ~ .container .mobile-menu-btn .icon-hamburger { display: none; }
.menu-toggle-checkbox:checked ~ .container .mobile-menu-btn .icon-close { display: block; }
.icon-close { display: none; }

@media (min-width: 768px) {
  .mobile-menu-btn { display: none; }
}

/* 移动端菜单面板（白色） */
.mobile-menu {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255, 255, 255, 0.97);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  z-index: 40;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2rem;
}

.menu-toggle-checkbox:checked ~ .mobile-menu {
  display: flex;
}

.mobile-menu .nav-link {
  font-size: 1.25rem;
  padding: 0.75rem 1.5rem;
}

/* ----- 按钮 ----- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  cursor: pointer;
  border: none;
  font-family: inherit;
  letter-spacing: 0.025em;
  white-space: nowrap;
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  padding: 0.625rem 1.5rem;
  font-size: 0.875rem;
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.25), 0 0 0 1px rgba(59, 130, 246, 0.1);
}

.btn-primary:hover {
  background: linear-gradient(135deg, var(--color-primary-bright), var(--color-primary));
  box-shadow: 0 4px 16px rgba(37, 99, 235, 0.35), 0 0 0 1px rgba(59, 130, 246, 0.2);
  transform: translateY(-2px);
}

.btn-secondary {
  background: var(--color-primary-soft);
  color: var(--color-primary);
  padding: 0.625rem 1.5rem;
  font-size: 0.875rem;
  border: 1px solid rgba(59, 130, 246, 0.18);
}

.btn-secondary:hover {
  background: #dbeafe;
  border-color: rgba(59, 130, 246, 0.40);
  color: var(--color-primary-dark);
  transform: translateY(-2px);
}

.btn-lg {
  padding: 0.875rem 2rem;
  font-size: 1rem;
  border-radius: var(--radius-lg);
}

@media (min-width: 768px) {
  .btn-lg { padding: 1rem 2.5rem; font-size: 1.05rem; }
}

/* ============================================================
   1. Hero — 左右分栏
   ============================================================ */
.hero {
  position: relative;
  padding: 6rem 1rem 2rem;
  overflow: hidden;
  background: linear-gradient(180deg, #eff6ff 0%, var(--color-bg) 100%);
}

@media (min-width: 768px) {
  .hero { padding: 8rem 1rem 4rem; }
}

.hero-grid {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3rem;
  max-width: 1200px;
  margin: 0 auto;
}

@media (min-width: 1024px) {
  .hero-grid {
    flex-direction: row;
    gap: 4rem;
  }
}

/* 左侧文案 */
.hero-text {
  flex: 0 0 55%;
  text-align: center;
}

@media (min-width: 1024px) {
  .hero-text { text-align: left; }
}

@media (min-width: 768px) {
  .hero-text { flex: 0 0 52%; }
}

/* 双徽章 */
.hero-badges {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 2rem;
  justify-content: center;
  flex-wrap: wrap;
}

@media (min-width: 1024px) {
  .hero-badges { justify-content: flex-start; }
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.4rem 1rem;
  border-radius: 9999px;
  background: rgba(59, 130, 246, 0.06);
  border: 1px solid rgba(59, 130, 246, 0.12);
  font-size: 0.82rem;
  color: var(--color-primary);
  font-weight: 500;
}

.badge-dot {
  width: 0.4rem;
  height: 0.4rem;
  border-radius: 50%;
  background: var(--color-primary);
  box-shadow: 0 0 6px rgba(59, 130, 246, 0.3);
  animation: pulse-dot 2s ease-in-out infinite;
}

.hero-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-text);
  font-family: var(--font-display);
  margin-bottom: 1.25rem;
  line-height: 1.2;
}

@media (min-width: 640px) {
  .hero-title { font-size: 2.75rem; }
}

@media (min-width: 768px) {
  .hero-title { font-size: 3.5rem; }
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  max-width: 32rem;
  margin: 0 auto 2rem;
  line-height: 1.75;
}

@media (min-width: 1024px) {
  .hero-desc { margin: 0 0 2rem 0; }
}

/* Hero 按钮组 */
.hero-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  margin-bottom: 2.5rem;
  flex-wrap: wrap;
}

@media (min-width: 1024px) {
  .hero-actions { justify-content: flex-start; }
}

/* 横排统计条 */
.stat-strip {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  justify-content: center;
  flex-wrap: wrap;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-lg);
  background: rgba(59, 130, 246, 0.04);
  border: 1px solid rgba(59, 130, 246, 0.08);
}

@media (min-width: 1024px) {
  .stat-strip { justify-content: flex-start; }
}

.stat-strip-item {
  font-size: 0.85rem;
  color: var(--color-primary);
  letter-spacing: 0.03em;
  font-weight: 500;
}

.stat-strip-divider {
  width: 1px;
  height: 1rem;
  background: rgba(59, 130, 246, 0.15);
}

/* 右侧图形 */
.hero-visual {
  flex: 0 0 45%;
  display: none;
}

@media (min-width: 1024px) {
  .hero-visual {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 320px;
  }
}

/* 纯 CSS 抽象网络图 */
.network-graphic {
  position: relative;
  width: 280px;
  height: 280px;
}

.network-node {
  position: absolute;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--color-primary);
  box-shadow: 0 0 12px rgba(59, 130, 246, 0.25);
}

.network-node.n1 { top: 20%; left: 50%; }
.network-node.n2 { top: 50%; left: 20%; }
.network-node.n3 { top: 50%; right: 20%; }
.network-node.n4 { bottom: 20%; left: 50%; }
.network-node.n5 { top: 10%; left: 30%; background: var(--color-accent); box-shadow: 0 0 12px rgba(6, 182, 212, 0.25); }
.network-node.n6 { bottom: 10%; left: 70%; background: var(--color-violet); box-shadow: 0 0 12px rgba(139, 92, 246, 0.25); }

/* 大圆心 */
.network-center {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 80px;
  height: 80px;
  border-radius: 50%;
  border: 2px dashed rgba(59, 130, 246, 0.18);
  display: flex;
  align-items: center;
  justify-content: center;
}

.network-center-inner {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: var(--color-primary);
  box-shadow: 0 0 20px rgba(59, 130, 246, 0.3);
  animation: pulse-dot 3s ease-in-out infinite;
}

/* 连接环 */
.network-ring {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 200px;
  height: 200px;
  border-radius: 50%;
  border: 1px solid rgba(59, 130, 246, 0.10);
}

.network-ring.r2 {
  width: 260px;
  height: 260px;
  border-color: rgba(6, 182, 212, 0.06);
}

/* ============================================================
   2. Problem — 交替左右行
   ============================================================ */
.problem-section {
  position: relative;
  background: var(--color-surface);
}

.problem-row {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
  margin-bottom: 3rem;
  padding: 2rem;
  border-radius: var(--radius-2xl);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  transition: border-color var(--transition-normal), box-shadow var(--transition-normal);
}

.problem-row:hover {
  border-color: var(--color-border-hover);
  box-shadow: var(--shadow-md);
}

.problem-row:last-child {
  margin-bottom: 0;
}

@media (min-width: 768px) {
  .problem-row {
    flex-direction: row;
    gap: 3rem;
    margin-bottom: 2.5rem;
  }
  .problem-row.reverse {
    flex-direction: row-reverse;
  }
}

/* 水印编号 + 图标 */
.problem-visual {
  position: relative;
  flex-shrink: 0;
  width: 160px;
  height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.watermark-num {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 7rem;
  font-weight: 800;
  color: rgba(59, 130, 246, 0.04);
  font-family: var(--font-display);
  line-height: 1;
  user-select: none;
  pointer-events: none;
}

.problem-icon {
  position: relative;
  z-index: 1;
  width: 68px;
  height: 68px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-xl);
  background: linear-gradient(135deg, var(--color-primary-soft), #dbeafe);
  border: 1px solid rgba(59, 130, 246, 0.15);
}

.problem-icon svg {
  width: 30px;
  height: 30px;
  color: var(--color-primary);
}

/* 右侧/左侧文字 */
.problem-text {
  flex: 1;
  text-align: center;
}

@media (min-width: 768px) {
  .problem-text { text-align: left; }
}

.problem-text h3 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

@media (min-width: 768px) {
  .problem-text h3 { font-size: 1.5rem; }
}

.problem-text p {
  color: var(--color-text-secondary);
  line-height: 1.7;
  font-size: 0.95rem;
}

@media (min-width: 768px) {
  .problem-text p { font-size: 1.05rem; }
}

/* ============================================================
   3. How It Works — 横向 4 步流程
   ============================================================ */
.pipeline {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
}

@media (min-width: 768px) {
  .pipeline {
    flex-direction: row;
    align-items: flex-start;
    gap: 0;
  }
}

.pipeline-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  flex: 1;
  position: relative;
  padding: 0 1rem;
}

/* 桌面：横向连线 */
@media (min-width: 768px) {
  .pipeline-step::after {
    content: '';
    position: absolute;
    top: 28px;
    left: calc(50% + 28px);
    width: calc(100% - 56px);
    height: 1px;
    background: linear-gradient(90deg, rgba(59, 130, 246, 0.20), rgba(59, 130, 246, 0.04));
  }
  .pipeline-step:last-child::after {
    display: none;
  }
}

/* 手机：纵向连线 */
@media (max-width: 767px) {
  .pipeline-step::after {
    content: '';
    position: absolute;
    top: 56px;
    left: 50%;
    width: 1px;
    height: 2rem;
    background: linear-gradient(180deg, rgba(59, 130, 246, 0.20), rgba(59, 130, 246, 0.04));
  }
  .pipeline-step:last-child::after {
    display: none;
  }
}

.step-circle {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-primary);
  background: linear-gradient(135deg, var(--color-primary-soft), #dbeafe);
  border: 2px solid rgba(59, 130, 246, 0.20);
  box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.04);
  margin-bottom: 1rem;
  position: relative;
  z-index: 1;
  flex-shrink: 0;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.pipeline-step:hover .step-circle {
  transform: scale(1.08);
  box-shadow: 0 0 0 8px rgba(59, 130, 246, 0.08);
}

.pipeline-step h4 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
}

@media (min-width: 768px) {
  .pipeline-step h4 { font-size: 1.15rem; }
}

.pipeline-step p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  max-width: 200px;
}

@media (min-width: 768px) {
  .pipeline-step p { font-size: 0.9rem; }
}

/* ============================================================
   4. Features — 非对称 Bento 网格
   ============================================================ */
.bento-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 768px) {
  .bento-grid {
    grid-template-columns: repeat(4, 1fr);
    grid-auto-rows: 1fr;
    gap: 1.25rem;
  }
}

.bento-card {
  background: var(--color-panel-bg);
  border: 1px solid var(--color-panel-border);
  border-radius: var(--radius-2xl);
  padding: 1.75rem;
  box-shadow: var(--shadow-card);
  transition: border-color var(--transition-normal), transform var(--transition-normal), box-shadow var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.bento-card::after {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 4rem;
  height: 4rem;
  background: linear-gradient(135deg, transparent 50%, rgba(59, 130, 246, 0.03) 50%);
  border-radius: 0 var(--radius-2xl) 0 0;
}

.bento-card:hover {
  border-color: var(--color-border-hover);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg), var(--shadow-glow);
}

@media (min-width: 768px) {
  .bento-card.span-2 { grid-column: span 2; }
  .bento-card.span-2-row { grid-column: span 2; grid-row: span 2; }
  .bento-card.span-4 { grid-column: span 4; }
}

.bento-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 3rem;
  height: 3rem;
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, var(--color-primary-soft), #dbeafe);
  border: 1px solid rgba(59, 130, 246, 0.12);
  margin-bottom: 1.25rem;
}

.bento-icon svg {
  width: 1.4rem;
  height: 1.4rem;
  color: var(--color-primary);
}

.bento-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

@media (min-width: 768px) {
  .bento-card h3 { font-size: 1.2rem; }
}

.bento-card p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.65;
}

/* 特色大卡片渐变背景 */
.bento-featured {
  background: linear-gradient(135deg, #ffffff, #eff6ff, #ecfeff);
  border-color: rgba(59, 130, 246, 0.15);
}

/* ============================================================
   5. Protocol — 代码展示区
   ============================================================ */
.protocol-section {
  position: relative;
  background: var(--color-surface);
}

.protocol-content {
  max-width: 720px;
  margin: 0 auto;
}

.code-block {
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-xl);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.code-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  background: rgba(0, 0, 0, 0.15);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.code-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.code-dot.red { background: #ef4444; }
.code-dot.yellow { background: #eab308; }
.code-dot.green { background: #22c55e; }

.code-filename {
  margin-left: 0.5rem;
  font-size: 0.75rem;
  color: #94a3b8;
  font-family: 'SF Mono', 'Cascadia Code', 'Consolas', monospace;
}

.code-body {
  padding: 1.25rem;
  overflow-x: auto;
}

.code-body pre {
  font-family: 'SF Mono', 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.84rem;
  line-height: 1.8;
  color: #e2e8f0;
  white-space: pre;
}

.code-key { color: #93c5fd; }
.code-str  { color: #6ee7b7; }
.code-num  { color: #fcd34d; }
.code-comment { color: #7c8da6; }

.protocol-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-top: 1.5rem;
  color: var(--color-primary);
  font-weight: 500;
  font-size: 0.95rem;
  transition: color var(--transition-fast);
}

.protocol-link:hover { color: var(--color-primary-dark); }

.protocol-link svg {
  width: 1rem;
  height: 1rem;
}

/* 协议区统计 */
.protocol-stats {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-top: 2.5rem;
  flex-wrap: wrap;
}

.protocol-stat {
  text-align: center;
}

.protocol-stat-num {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  font-family: var(--font-display);
}

.protocol-stat-label {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: 0.2rem;
}

/* ============================================================
   6. Download — 纯 CSS 手机模型
   ============================================================ */
.download-grid {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2.5rem;
}

@media (min-width: 768px) {
  .download-grid {
    flex-direction: row;
    justify-content: center;
    gap: 4rem;
  }
}

.download-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
}

/* CSS 手机模型 */
.device-mockup {
  position: relative;
  width: 160px;
  height: 310px;
  border-radius: 1.8rem;
  background: #f1f5f9;
  border: 3px solid #e2e8f0;
  padding: 12px 8px;
  box-shadow: var(--shadow-md);
}

@media (min-width: 768px) {
  .device-mockup {
    width: 180px;
    height: 350px;
    border-radius: 2rem;
    padding: 14px 8px;
  }
}

.device-mockup::before {
  content: '';
  position: absolute;
  top: 9px;
  left: 50%;
  transform: translateX(-50%);
  width: 50px;
  height: 5px;
  border-radius: 3px;
  background: #cbd5e1;
}

.device-screen {
  width: 100%;
  height: 100%;
  border-radius: 1.2rem;
  background: linear-gradient(180deg, #dbeafe 0%, #eff6ff 100%);
  padding: 1rem 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 8px;
  overflow: hidden;
}

/* 模拟消息条 */
.msg-bar {
  height: 8px;
  border-radius: 4px;
  background: rgba(59, 130, 246, 0.18);
}

.msg-bar.w60 { width: 60%; }
.msg-bar.w80 { width: 80%; }
.msg-bar.w45 { width: 45%; }
.msg-bar.w70 { width: 70%; }
.msg-bar.accent { background: rgba(6, 182, 212, 0.25); }

.msg-avatar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 4px 0;
}

.msg-avatar-circle {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: rgba(59, 130, 246, 0.35);
  flex-shrink: 0;
}

.msg-avatar-circle.accent {
  background: rgba(6, 182, 212, 0.35);
}

/* 手机光晕 */
.device-glow {
  position: absolute;
  border-radius: 50%;
  filter: blur(50px);
  z-index: -1;
  pointer-events: none;
}

.device-glow.blue {
  width: 140px;
  height: 110px;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.10), transparent 60%);
  top: 40%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.device-glow.cyan {
  width: 140px;
  height: 110px;
  background: radial-gradient(circle, rgba(6, 182, 212, 0.08), transparent 60%);
  top: 40%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.download-label {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-text);
}

.download-note {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: 1.5rem;
  text-align: center;
}

/* ============================================================
   7. FAQ — 原生 details 手风琴
   ============================================================ */
.faq-list {
  max-width: 680px;
  margin: 0 auto;
}

.faq-item {
  border-bottom: 1px solid var(--color-border);
}

.faq-item:first-child {
  border-top: 1px solid var(--color-border);
}

.faq-item summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 0;
  cursor: pointer;
  color: var(--color-text);
  font-weight: 600;
  font-size: 1.05rem;
  list-style: none;
  transition: color var(--transition-fast);
}

.faq-item summary:hover {
  color: var(--color-primary);
}

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

.faq-item summary::after {
  content: '+';
  flex-shrink: 0;
  width: 24px;
  height: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 300;
  color: var(--color-text-muted);
  transition: transform var(--transition-fast);
  margin-left: 1rem;
}

.faq-item[open] summary::after {
  content: '−';
  color: var(--color-primary);
}

.faq-item[open] summary {
  color: var(--color-primary);
}

.faq-answer {
  padding: 0 0 1.5rem;
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* ============================================================
   8. CTA Banner — 底部转化（蓝色渐变醒目区域）
   ============================================================ */
.cta-banner {
  position: relative;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark), #1d4ed8);
  padding: 4rem 1rem;
  text-align: center;
  color: #fff;
}

.cta-banner h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  color: #fff;
}

@media (min-width: 768px) {
  .cta-banner h2 { font-size: 2rem; }
}

.cta-banner p {
  color: rgba(255, 255, 255, 0.8);
  margin-bottom: 2rem;
  font-size: 1.05rem;
}

.cta-banner .hero-actions {
  margin-bottom: 0;
  justify-content: center;
}

/* CTA 区域内的按钮覆盖 */
.cta-banner .btn-primary {
  background: #fff;
  color: var(--color-primary);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.cta-banner .btn-primary:hover {
  background: #f1f5f9;
  color: var(--color-primary-dark);
  box-shadow: 0 6px 24px rgba(0, 0, 0, 0.2);
}

.cta-banner .btn-secondary {
  border-color: rgba(255, 255, 255, 0.5);
  color: #fff;
  background: rgba(255, 255, 255, 0.08);
}

.cta-banner .btn-secondary:hover {
  border-color: rgba(255, 255, 255, 0.8);
  color: #fff;
  background: rgba(255, 255, 255, 0.15);
}

/* ============================================================
   9. Footer — 极简
   ============================================================ */
.footer-simple {
  padding: 2.5rem 1rem;
  text-align: center;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
}

.footer-simple-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
}

@media (min-width: 768px) {
  .footer-simple-inner {
    flex-direction: row;
    justify-content: space-between;
  }
}

.footer-brand-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.footer-brand-row img {
  width: 1.5rem;
  height: 1.5rem;
  border-radius: var(--radius-md);
}

.footer-brand-row span {
  color: var(--color-text);
  font-weight: 600;
  font-family: var(--font-display);
  letter-spacing: 0.1em;
}

.footer-tagline {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.footer-links-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-links-row a {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.footer-links-row a:hover {
  color: var(--color-primary);
}

.footer-dot {
  color: var(--color-text-muted);
  font-size: 0.7rem;
  opacity: 0.5;
}

.footer-copy-simple {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

/* ----- 动画 ----- */
@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* 减少动画偏好 */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  html { scroll-behavior: auto; }
}

/* ----- 错误页面（404 / 502）----- */
.error-page {
  height: 100%;
  min-height: 100vh;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  font-family: var(--font-sans);
}

.error-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  padding-top: 12%;
  text-align: center;
}

.error-logo img {
  display: block;
  width: 100px;
  margin: 0 auto;
}

.error-logo img + img {
  margin-top: 12px;
}

.error-code {
  margin-top: 24px;
  font-size: 110px;
  color: var(--color-primary);
  letter-spacing: 10px;
  font-weight: 700;
  font-family: var(--font-display);
  text-shadow: 0 0 40px rgba(59, 130, 246, 0.15);
}

.error-msg {
  margin-top: 8px;
  font-size: 18px;
  color: var(--color-text-muted);
}

.error-link {
  margin-top: 24px;
  font-size: 16px;
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.error-link:hover {
  color: var(--color-primary-dark);
}

/* ----- 工具类 ----- */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.text-center { text-align: center; }
.relative { position: relative; }
.z-10 { z-index: 10; }