/* ========== 设计系统 ========== */
:root {
  --color-bg: #000;
  --color-bg-secondary: #111;
  --color-bg-card: rgba(255, 255, 255, 0.04);
  --color-text: #f5f5f7;
  --color-text-secondary: #86868b;
  --color-text-tertiary: #6e6e73;
  --color-accent: #2997ff;
  --color-accent-hover: #0077ed;
  --color-border: rgba(255, 255, 255, 0.08);
  --color-glass: rgba(255, 255, 255, 0.06);
  --font-sans: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'SF Pro Text', 'Helvetica Neue', sans-serif;
  --font-mono: 'SF Mono', SFMono-Regular, ui-monospace, monospace;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --transition-base: 0.3s cubic-bezier(0.25, 0.1, 0.25, 1);
  --transition-spring: 0.6s cubic-bezier(0.16, 1, 0.3, 1);
  --max-width: 980px;
  --max-width-wide: 1200px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
  overflow-x: hidden;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition-base);
}

a:hover {
  color: var(--color-accent-hover);
}

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

/* ========== 导航 ========== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(0, 0, 0, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--color-border);
  height: 48px;
  transition: background var(--transition-base);
}

.nav-inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-logo-icon {
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--color-accent), #5856d6);
  border-radius: 7px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}

.nav-links {
  display: flex;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  color: var(--color-text-secondary);
  font-size: 14px;
  font-weight: 400;
  transition: color var(--transition-base);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-text);
}

.nav-cta {
  background: var(--color-accent);
  color: #fff !important;
  padding: 6px 16px;
  border-radius: 980px;
  font-size: 13px;
  font-weight: 500;
  transition: background var(--transition-base);
}

.nav-cta:hover {
  background: var(--color-accent-hover);
  color: #fff !important;
}

/* 语言切换 */
.lang-switcher {
  position: relative;
  margin-left: 8px;
}

.lang-switcher-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 12px;
  border-radius: 980px;
  font-size: 13px;
  font-weight: 500;
  border: 1px solid var(--color-border);
  background: transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
  line-height: 1.4;
}

.lang-switcher-btn:hover,
.lang-switcher.open .lang-switcher-btn {
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-text);
  border-color: rgba(255, 255, 255, 0.2);
}

.lang-switcher-icon {
  font-size: 14px;
}

.lang-switcher-arrow {
  font-size: 10px;
  transition: transform var(--transition-base);
}

.lang-switcher.open .lang-switcher-arrow {
  transform: rotate(180deg);
}

.lang-dropdown {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 160px;
  background: rgba(28, 28, 30, 0.98);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 6px;
  z-index: 200;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
}

.lang-switcher.open .lang-dropdown {
  display: block;
}

.lang-dropdown a {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  color: var(--color-text-secondary);
  transition: all var(--transition-base);
  text-decoration: none;
}

.lang-dropdown a:hover {
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-text);
}

.lang-dropdown a.active {
  color: var(--color-accent);
}

.lang-dropdown a.active::after {
  content: '✓';
  margin-left: auto;
  font-size: 12px;
}

/* 移动端菜单 */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--color-text);
  font-size: 24px;
  cursor: pointer;
  padding: 4px;
}

/* ========== 通用区块 ========== */
.section {
  padding: 100px 24px;
}

.section-compact {
  padding: 60px 24px;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
}

.container-wide {
  max-width: var(--max-width-wide);
  margin: 0 auto;
}

/* ========== 排版 ========== */
.headline-xl {
  font-size: clamp(40px, 7vw, 80px);
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1.05;
}

.headline-lg {
  font-size: clamp(32px, 5vw, 56px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.headline-md {
  font-size: clamp(24px, 3.5vw, 40px);
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.15;
}

.headline-sm {
  font-size: clamp(20px, 2.5vw, 28px);
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.2;
}

.body-lg {
  font-size: 21px;
  line-height: 1.5;
  color: var(--color-text-secondary);
}

.body-md {
  font-size: 17px;
  line-height: 1.6;
  color: var(--color-text-secondary);
}

.body-sm {
  font-size: 14px;
  line-height: 1.5;
  color: var(--color-text-tertiary);
}

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

.text-gradient {
  background: linear-gradient(90deg, #2997ff, #5856d6, #af52de);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ========== 按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: 980px;
  font-size: 17px;
  font-weight: 500;
  border: none;
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  color: #fff;
  transform: scale(1.02);
}

.btn-secondary {
  background: transparent;
  color: var(--color-accent);
  border: 1px solid rgba(41, 151, 255, 0.3);
}

.btn-secondary:hover {
  background: rgba(41, 151, 255, 0.08);
  color: var(--color-accent);
}

.btn-icon {
  font-size: 20px;
}

/* ========== 卡片 ========== */
.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 40px;
  transition: all var(--transition-base);
}

.card:hover {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(255, 255, 255, 0.12);
}

.card-glass {
  background: var(--color-glass);
  backdrop-filter: blur(40px);
  -webkit-backdrop-filter: blur(40px);
}

/* ========== 网格 ========== */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

/* ========== 动画 ========== */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1),
              transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.fade-in-up {
  opacity: 0;
  transform: translateY(50px);
  transition: opacity 1s cubic-bezier(0.16, 1, 0.3, 1),
              transform 1s cubic-bezier(0.16, 1, 0.3, 1);
}

.fade-in-up.visible {
  opacity: 1;
  transform: translateY(0);
}

.scale-in {
  opacity: 0;
  transform: scale(0.92);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1),
              transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.scale-in.visible {
  opacity: 1;
  transform: scale(1);
}

.stagger-1 { transition-delay: 0.1s; }
.stagger-2 { transition-delay: 0.2s; }
.stagger-3 { transition-delay: 0.3s; }
.stagger-4 { transition-delay: 0.4s; }
.stagger-5 { transition-delay: 0.5s; }

/* ========== 分隔线 ========== */
.divider {
  height: 1px;
  background: var(--color-border);
  border: none;
  margin: 0;
}

/* ========== 页脚 ========== */
.footer {
  padding: 40px 24px;
  border-top: 1px solid var(--color-border);
}

.footer-inner {
  max-width: var(--max-width-wide);
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-links {
  display: flex;
  gap: 24px;
  list-style: none;
}

.footer-links a {
  color: var(--color-text-tertiary);
  font-size: 13px;
}

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

.footer-copy {
  font-size: 13px;
  color: var(--color-text-tertiary);
}

/* ========== 布局演示组件 ========== */
.layout-demo {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 12px;
  aspect-ratio: 16 / 10;
  display: grid;
  gap: 6px;
}

.layout-demo .tile {
  background: rgba(41, 151, 255, 0.12);
  border: 1px solid rgba(41, 151, 255, 0.2);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  color: var(--color-accent);
  font-weight: 500;
  transition: all var(--transition-base);
}

.layout-demo:hover .tile {
  background: rgba(41, 151, 255, 0.18);
  border-color: rgba(41, 151, 255, 0.35);
}

/* 布局变体 */
.layout-h2 { grid-template-columns: 1fr 1fr; }
.layout-v2 { grid-template-rows: 1fr 1fr; }
.layout-7030 { grid-template-columns: 7fr 3fr; }
.layout-3070 { grid-template-columns: 3fr 7fr; }
.layout-3col { grid-template-columns: 1fr 1fr 1fr; }
.layout-grid { grid-template-columns: 1fr 1fr; grid-template-rows: 1fr 1fr; }

/* ========== 快捷键标签 ========== */
.kbd {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: 6px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--color-text-secondary);
  white-space: nowrap;
}

/* ========== 步骤指示器 ========== */
.step-number {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--color-accent);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  font-weight: 600;
  flex-shrink: 0;
}

/* ========== 响应式 ========== */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 48px;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    padding: 20px 24px;
    gap: 16px;
    border-bottom: 1px solid var(--color-border);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-toggle {
    display: block;
  }

  .lang-dropdown {
    right: auto;
    left: 0;
  }

  .section {
    padding: 60px 20px;
  }

  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }

  .card {
    padding: 24px;
  }

  .footer-inner {
    flex-direction: column;
    gap: 16px;
    text-align: center;
  }

  .footer-links {
    flex-wrap: wrap;
    justify-content: center;
  }
}

@media (max-width: 480px) {
  .grid-2 {
    grid-template-columns: 1fr;
  }

  .btn {
    padding: 10px 24px;
    font-size: 15px;
  }
}