/* ============================================
   电池博士 / Battery Doctor — 全局样式
   ============================================ */

/* --- CSS Variables --- */
:root {
  --bg-primary: #080f1a;
  --bg-secondary: #0d1b2e;
  --bg-card: #111d30;
  --bg-card-hover: #152238;
  --border: #1e3350;
  --border-light: #253d5e;
  --accent: #00a8ff;
  --accent-hover: #33bbff;
  --accent-glow: rgba(0, 168, 255, 0.15);
  --green: #00e676;
  --green-glow: rgba(0, 230, 118, 0.15);
  --text-primary: #e0e6f0;
  --text-secondary: #8899b4;
  --text-muted: #5a6d85;
  --gradient-blue: linear-gradient(135deg, #00a8ff, #0077ff);
  --gradient-green: linear-gradient(135deg, #00e676, #00c853);
  --radius: 8px;
  --radius-lg: 16px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 40px var(--accent-glow);
  --transition: 0.3s ease;
}

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

main { flex: 1; }

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

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

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

/* --- Header --- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(8, 15, 26, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), box-shadow var(--transition);
}

.header.scrolled {
  background: rgba(8, 15, 26, 0.95);
  box-shadow: 0 2px 20px rgba(0, 0, 0, 0.3);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text-primary);
  text-decoration: none;
}

.logo:hover { color: var(--text-primary); }

.logo-icon { flex-shrink: 0; }

.logo-text {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.logo-sub {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  padding-left: 10px;
  border-left: 1px solid var(--border);
}

.nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.nav-link {
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  position: relative;
  transition: color var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--text-primary);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  border-radius: 1px;
  transition: width var(--transition);
}

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

.nav-btn {
  background: var(--gradient-blue);
  color: #fff !important;
  padding: 8px 20px;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 600;
  transition: transform var(--transition), box-shadow var(--transition);
}

.nav-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(0, 168, 255, 0.3);
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 1px;
  transition: transform var(--transition), opacity var(--transition);
}

.menu-toggle.open span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.menu-toggle.open span:nth-child(2) { opacity: 0; }
.menu-toggle.open span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* --- Hero --- */
.hero {
  padding: 160px 0 120px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(ellipse at center, rgba(0, 168, 255, 0.06) 0%, transparent 70%);
  pointer-events: none;
}

.hero-subtitle {
  display: inline-block;
  background: rgba(0, 168, 255, 0.1);
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 6px 16px;
  border-radius: 20px;
  border: 1px solid rgba(0, 168, 255, 0.2);
  margin-bottom: 24px;
  letter-spacing: 0.5px;
}

.hero-title {
  font-size: clamp(2.5rem, 5vw, 3.8rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  letter-spacing: -1px;
}

.hero-title .highlight {
  background: var(--gradient-blue);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 40px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: transform var(--transition), box-shadow var(--transition);
}

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

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0, 168, 255, 0.35);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-light);
}

.btn-outline:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

/* --- Sections --- */
.section {
  padding: 100px 0;
}

.section-label {
  display: inline-block;
  color: var(--accent);
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 12px;
}

.section-title {
  font-size: clamp(1.8rem, 3.5vw, 2.5rem);
  font-weight: 700;
  margin-bottom: 16px;
  letter-spacing: -0.5px;
}

.section-desc {
  color: var(--text-secondary);
  font-size: 1.05rem;
  max-width: 600px;
  margin-bottom: 48px;
}

.text-center { text-align: center; }
.text-center .section-desc { margin-left: auto; margin-right: auto; }

/* --- Cards --- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: transform var(--transition), border-color var(--transition),
              box-shadow var(--transition);
}

.card:hover {
  transform: translateY(-4px);
  border-color: var(--border-light);
  box-shadow: var(--shadow), var(--shadow-glow);
}

.card-icon {
  width: 52px;
  height: 52px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  background: var(--accent-glow);
}

.card-icon.green { background: var(--green-glow); }

.card h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 10px;
}

.card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* --- Stats --- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 24px;
}

.stat-item {
  text-align: center;
  padding: 40px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

.stat-number {
  font-size: 2.8rem;
  font-weight: 800;
  background: var(--gradient-blue);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  margin-bottom: 8px;
}

.stat-label {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.stat-unit {
  font-size: 1.2rem;
  font-weight: 600;
  -webkit-text-fill-color: var(--accent);
}

/* --- CTA Section --- */
.cta-section {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 64px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta-section::before {
  content: '';
  position: absolute;
  top: -100px;
  left: 50%;
  transform: translateX(-50%);
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, var(--accent-glow) 0%, transparent 70%);
  pointer-events: none;
}

.cta-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.cta-desc {
  color: var(--text-secondary);
  margin-bottom: 32px;
}

/* --- Footer --- */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 64px 0 0;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  padding-bottom: 48px;
}

.footer-col h4 {
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.footer-col a {
  display: block;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 10px;
  transition: color var(--transition);
}

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

.footer-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  color: var(--text-primary);
  font-size: 1.1rem;
  font-weight: 700;
  text-decoration: none;
}

.footer-desc {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 0;
  border-top: 1px solid var(--border);
  font-size: 0.85rem;
  color: var(--text-muted);
  flex-wrap: wrap;
  gap: 8px;
}

.footer-icp { color: var(--text-muted); }

/* --- Page Header (inner pages) --- */
.page-header {
  padding: 140px 0 60px;
  text-align: center;
  position: relative;
}

.page-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 500px;
  height: 300px;
  background: radial-gradient(ellipse at center, var(--accent-glow) 0%, transparent 70%);
  pointer-events: none;
}

.page-title {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 800;
  letter-spacing: -1px;
  margin-bottom: 12px;
}

.page-subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
}

/* --- Feature List --- */
.feature-list {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 16px;
}

.feature-list li {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.feature-list .check-icon {
  flex-shrink: 0;
  margin-top: 2px;
}

.feature-list h4 {
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.feature-list p {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

/* --- Contact Form --- */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: start;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-secondary);
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 12px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text-primary);
  font-size: 0.95rem;
  font-family: inherit;
  transition: border-color var(--transition), box-shadow var(--transition);
  outline: none;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.form-group textarea { resize: vertical; min-height: 120px; }

.form-group select { cursor: pointer; appearance: none; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' fill='%238899b4'%3E%3Cpath d='M1 1l5 5 5-5'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 16px center; padding-right: 40px; }

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.contact-info-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.contact-info-item h4 {
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.contact-info-item p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* --- Blog --- */
.blog-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 28px;
}

.blog-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition), border-color var(--transition),
              box-shadow var(--transition);
}

.blog-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-light);
  box-shadow: var(--shadow);
}

.blog-card-image {
  height: 200px;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  border-bottom: 1px solid var(--border);
}

.blog-card-body {
  padding: 24px;
}

.blog-card-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-glow);
  padding: 4px 12px;
  border-radius: 12px;
  margin-bottom: 12px;
}

.blog-card h3 {
  font-size: 1.1rem;
  margin-bottom: 8px;
  line-height: 1.4;
}

.blog-card p {
  color: var(--text-secondary);
  font-size: 0.88rem;
  margin-bottom: 16px;
  line-height: 1.6;
}

.blog-card-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* --- Product Tabs --- */
.tabs {
  display: flex;
  gap: 4px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 4px;
  margin-bottom: 40px;
  width: fit-content;
  flex-wrap: wrap;
}

.tab-btn {
  padding: 10px 24px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  border-radius: 6px;
  transition: all var(--transition);
  font-family: inherit;
}

.tab-btn:hover { color: var(--text-primary); }

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

.tab-panel { display: none; }
.tab-panel.active { display: block; animation: fadeIn 0.4s ease; }

/* --- Solution Cards --- */
.solution-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 40px;
  display: flex;
  gap: 32px;
  align-items: center;
  margin-bottom: 24px;
  transition: transform var(--transition), border-color var(--transition);
}

.solution-card:hover {
  transform: translateX(6px);
  border-color: var(--border-light);
}

.solution-card-icon {
  width: 80px;
  height: 80px;
  flex-shrink: 0;
  border-radius: 16px;
  background: var(--accent-glow);
  display: flex;
  align-items: center;
  justify-content: center;
}

.solution-card-content h3 {
  font-size: 1.2rem;
  margin-bottom: 8px;
}

.solution-card-content p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* --- About page --- */
.timeline {
  position: relative;
  padding-left: 32px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 8px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--border);
}

.timeline-item {
  position: relative;
  margin-bottom: 32px;
  padding-left: 24px;
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: -28px;
  top: 6px;
  width: 12px;
  height: 12px;
  background: var(--accent);
  border-radius: 50%;
  border: 3px solid var(--bg-primary);
}

.timeline-year {
  font-size: 0.8rem;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 4px;
}

.timeline-item h4 {
  font-size: 1rem;
  margin-bottom: 4px;
}

.timeline-item p {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

/* --- Animations --- */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes fadeInLeft {
  from { opacity: 0; transform: translateX(-20px); }
  to   { opacity: 1; transform: translateX(0); }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.animate-on-scroll {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.animate-on-scroll.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }

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

@media (max-width: 768px) {
  .menu-toggle { display: flex; }

  .nav {
    position: absolute;
    top: 68px;
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(8, 15, 26, 0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 24px;
    gap: 20px;
    border-bottom: 1px solid var(--border);
    display: none;
  }

  .nav.open { display: flex; }

  .hero { padding: 120px 0 80px; }

  .section { padding: 64px 0; }

  .cta-section { padding: 40px 24px; }

  .solution-card {
    flex-direction: column;
    padding: 28px;
  }

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

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .footer-bottom {
    flex-direction: column;
    text-align: center;
  }

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

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