/* ============================================================
   Chengdu Siwangyuan Technology Co., Ltd.
   Dark Theme Stylesheet
   ============================================================ */

/* --- CSS Variables --- */
:root {
  --bg-primary: #0a0e17;
  --bg-secondary: #111827;
  --bg-tertiary: #1a2235;
  --bg-card: #131c2e;
  --bg-card-hover: #1a2640;
  --text-primary: #e8edf5;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --accent-primary: #00d4ff;
  --accent-secondary: #0099cc;
  --accent-gradient: linear-gradient(135deg, #00d4ff, #0099cc);
  --accent-glow: rgba(0, 212, 255, 0.15);
  --border-color: #1e293b;
  --border-accent: rgba(0, 212, 255, 0.3);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.5);
  --shadow-accent: 0 4px 20px rgba(0, 212, 255, 0.15);
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
  --font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', Arial, sans-serif;
  --max-width: 1200px;
  --header-height: 72px;
}

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

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

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

ul {
  list-style: none;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 100px 0;
}

.section-dark {
  background-color: var(--bg-secondary);
}

.section-title {
  font-size: 2.4rem;
  font-weight: 700;
  margin-bottom: 16px;
  color: var(--text-primary);
  text-align: center;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
  text-align: center;
  max-width: 600px;
  margin: 0 auto 60px;
  line-height: 1.6;
}

/* --- Ambient Grid Background --- */
.ambient-grid {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-image:
    linear-gradient(rgba(0, 212, 255, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 212, 255, 0.03) 1px, transparent 1px);
  background-size: 60px 60px;
  pointer-events: none;
  z-index: 0;
}

/* --- Header / Navigation --- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(10, 14, 23, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition-normal);
}

.header.scrolled {
  background: rgba(10, 14, 23, 0.95);
  border-bottom-color: var(--border-color);
  box-shadow: var(--shadow-md);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
}

.logo-icon {
  width: 40px;
  height: 40px;
  background: var(--accent-gradient);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  font-weight: 800;
  color: #fff;
  flex-shrink: 0;
}

.logo span {
  color: var(--accent-primary);
}

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

.nav-link {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  position: relative;
  padding: 4px 0;
  transition: color var(--transition-fast);
}

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

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

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

.lang-toggle {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 8px 18px;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-family);
}

.lang-toggle:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: var(--accent-glow);
}

/* --- Mobile Menu --- */
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  z-index: 1001;
}

.mobile-menu-btn span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  margin: 5px 0;
  transition: all var(--transition-normal);
  border-radius: 2px;
}

.mobile-menu-btn.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.mobile-menu-btn.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-btn.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* --- Hero Section --- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--header-height);
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(0, 212, 255, 0.08) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -30%;
  left: -10%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(0, 153, 204, 0.06) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 20px;
  background: rgba(0, 212, 255, 0.1);
  border: 1px solid rgba(0, 212, 255, 0.2);
  border-radius: 50px;
  font-size: 0.85rem;
  color: var(--accent-primary);
  margin-bottom: 28px;
}

.hero-badge-dot {
  width: 8px;
  height: 8px;
  background: var(--accent-primary);
  border-radius: 50%;
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.3; }
}

.hero h1 {
  font-size: 3.6rem;
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 24px;
  background: linear-gradient(135deg, #ffffff 0%, #94a3b8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero h1 .highlight {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.2rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 40px;
  max-width: 600px;
}

.hero-buttons {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 32px;
  border-radius: 50px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-normal);
  font-family: var(--font-family);
  border: none;
  text-decoration: none;
}

.btn-primary {
  background: var(--accent-gradient);
  color: #fff;
  box-shadow: 0 4px 15px rgba(0, 212, 255, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 25px rgba(0, 212, 255, 0.4);
  color: #fff;
}

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

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

.btn-light {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-light:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: translateY(-2px);
}

/* --- Stats Section --- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.stat-card {
  text-align: center;
  padding: 40px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: all var(--transition-normal);
}

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

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

.stat-label {
  color: var(--text-secondary);
  font-size: 1rem;
}

/* --- Services Section --- */
.services-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.service-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 40px 32px;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.service-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: var(--accent-gradient);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-slow);
}

.service-card:hover::before {
  transform: scaleX(1);
}

.service-card:hover {
  border-color: var(--border-accent);
  transform: translateY(-6px);
  box-shadow: var(--shadow-accent);
}

.service-icon {
  width: 56px;
  height: 56px;
  background: var(--accent-glow);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  margin-bottom: 20px;
  color: var(--accent-primary);
}

.service-card h3 {
  font-size: 1.3rem;
  font-weight: 600;
  margin-bottom: 12px;
}

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

/* --- About Section --- */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.about-text h2 {
  font-size: 2.2rem;
  font-weight: 700;
  margin-bottom: 20px;
}

.about-text p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  font-size: 1rem;
  line-height: 1.8;
}

.about-features {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 24px;
}

.about-feature {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.about-feature-icon {
  color: var(--accent-primary);
  font-size: 1.1rem;
  flex-shrink: 0;
}

.about-visual {
  position: relative;
}

.about-image-placeholder {
  width: 100%;
  aspect-ratio: 4/3;
  background: var(--bg-tertiary);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  color: var(--accent-primary);
  position: relative;
  overflow: hidden;
}

.about-image-placeholder::before {
  content: '';
  position: absolute;
  width: 200px;
  height: 200px;
  background: radial-gradient(circle, rgba(0, 212, 255, 0.1) 0%, transparent 70%);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

/* --- Tech Stack --- */
.tech-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 20px;
}

.tech-item {
  padding: 16px 28px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.tech-item:hover {
  border-color: var(--border-accent);
  color: var(--accent-primary);
  box-shadow: var(--shadow-accent);
}

/* --- Process Section --- */
.process-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  position: relative;
}

.process-step {
  text-align: center;
  padding: 32px 20px;
  position: relative;
}

.process-step-number {
  width: 48px;
  height: 48px;
  background: var(--accent-gradient);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  font-weight: 700;
  color: #fff;
  margin: 0 auto 16px;
}

.process-step h4 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 8px;
}

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

/* --- Contact Section --- */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

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

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

.contact-item-icon {
  width: 44px;
  height: 44px;
  background: var(--accent-glow);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  color: var(--accent-primary);
  flex-shrink: 0;
}

.contact-item h4 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.contact-item p,
.contact-item a {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.contact-form {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 36px;
}

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

.form-group label {
  display: block;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 8px;
  color: var(--text-secondary);
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: 12px 16px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 0.95rem;
  font-family: var(--font-family);
  transition: border-color var(--transition-fast);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

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

.form-group select {
  cursor: pointer;
}

.form-group select option {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

.form-submit {
  width: 100%;
}

.form-success {
  display: none;
  text-align: center;
  padding: 40px 20px;
}

.form-success.show {
  display: block;
}

.form-success-icon {
  font-size: 3rem;
  margin-bottom: 16px;
}

.form-success h3 {
  font-size: 1.4rem;
  margin-bottom: 8px;
}

.form-success p {
  color: var(--text-secondary);
}

/* --- Footer --- */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 60px 0 0;
}

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

.footer-brand p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
  margin-top: 16px;
  max-width: 300px;
}

.footer h4 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.footer-links li {
  margin-bottom: 12px;
}

.footer-links a {
  color: var(--text-secondary);
  font-size: 0.9rem;
  transition: color var(--transition-fast);
}

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

.footer-bottom {
  border-top: 1px solid var(--border-color);
  padding: 24px 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-bottom p {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.footer-bottom-links {
  display: flex;
  gap: 20px;
}

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

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

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

.page-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: radial-gradient(ellipse at center, rgba(0, 212, 255, 0.05) 0%, transparent 60%);
  pointer-events: none;
}

.page-header h1 {
  font-size: 2.8rem;
  font-weight: 800;
  margin-bottom: 16px;
}

.page-header p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  max-width: 600px;
  margin: 0 auto;
}

/* --- About Page --- */
.mission-vision-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.mission-card,
.vision-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 40px 32px;
  transition: all var(--transition-normal);
}

.mission-card:hover,
.vision-card:hover {
  border-color: var(--border-accent);
  box-shadow: var(--shadow-accent);
}

.mission-card h3,
.vision-card h3 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.mission-card p,
.vision-card p {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.8;
}

.values-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.value-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 32px 24px;
  text-align: center;
  transition: all var(--transition-normal);
}

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

.value-icon {
  font-size: 2rem;
  margin-bottom: 16px;
  color: var(--accent-primary);
}

.value-card h4 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 8px;
}

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

/* --- Services Page --- */
.service-detail-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 40px 36px;
  margin-bottom: 24px;
  transition: all var(--transition-normal);
}

.service-detail-card:hover {
  border-color: var(--border-accent);
  box-shadow: var(--shadow-accent);
}

.service-detail-card h3 {
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.service-detail-card p {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.8;
  margin-bottom: 16px;
}

.service-detail-card ul {
  list-style: disc;
  padding-left: 20px;
}

.service-detail-card ul li {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 8px;
  line-height: 1.6;
}

.service-detail-card ul li::marker {
  color: var(--accent-primary);
}

/* --- Contact Page --- */
.contact-methods {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  margin-bottom: 48px;
}

.contact-method-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 36px 24px;
  text-align: center;
  transition: all var(--transition-normal);
}

.contact-method-card:hover {
  border-color: var(--border-accent);
  transform: translateY(-4px);
  box-shadow: var(--shadow-accent);
}

.contact-method-icon {
  font-size: 2.2rem;
  margin-bottom: 16px;
  color: var(--accent-primary);
}

.contact-method-card h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.contact-method-card p,
.contact-method-card a {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.contact-form-wide {
  max-width: 700px;
  margin: 0 auto;
}

/* --- Privacy & Terms Pages --- */
.legal-content {
  max-width: 850px;
  margin: 0 auto;
}

.legal-content .last-updated {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 40px;
  text-align: center;
}

.legal-section {
  margin-bottom: 36px;
}

.legal-section h2 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--accent-primary);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.legal-section h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 10px;
  margin-top: 20px;
  color: var(--text-primary);
}

.legal-section p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.8;
  margin-bottom: 12px;
}

.legal-section ul {
  list-style: disc;
  padding-left: 24px;
  margin-bottom: 12px;
}

.legal-section ul li {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
  margin-bottom: 6px;
}

.legal-section ul li::marker {
  color: var(--accent-primary);
}

/* --- Scroll Animations --- */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

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

.fade-in-left {
  opacity: 0;
  transform: translateX(-40px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

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

.fade-in-right {
  opacity: 0;
  transform: translateX(40px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

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

/* --- Back to Top --- */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 44px;
  height: 44px;
  background: var(--accent-gradient);
  border: none;
  border-radius: 50%;
  color: #fff;
  font-size: 1.2rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all var(--transition-normal);
  z-index: 999;
  box-shadow: 0 4px 15px rgba(0, 212, 255, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: 0 6px 25px rgba(0, 212, 255, 0.4);
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .hero h1 { font-size: 2.8rem; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .services-grid { grid-template-columns: repeat(2, 1fr); }
  .process-steps { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: repeat(2, 1fr); }
  .contact-methods { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .nav {
    position: fixed;
    top: 0;
    right: -100%;
    width: 280px;
    height: 100vh;
    background: var(--bg-secondary);
    border-left: 1px solid var(--border-color);
    flex-direction: column;
    padding: 100px 32px 32px;
    gap: 24px;
    transition: right var(--transition-normal);
    align-items: flex-start;
  }

  .nav.open {
    right: 0;
  }

  .mobile-menu-btn {
    display: block;
  }

  .hero h1 { font-size: 2.2rem; }
  .hero p { font-size: 1rem; }
  .section { padding: 60px 0; }
  .section-title { font-size: 1.8rem; }

  .about-grid { grid-template-columns: 1fr; gap: 40px; }
  .services-grid { grid-template-columns: 1fr; }
  .process-steps { grid-template-columns: 1fr 1fr; }
  .contact-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .mission-vision-grid { grid-template-columns: 1fr; }
  .values-grid { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .contact-methods { grid-template-columns: 1fr; }
  .tech-grid { gap: 12px; }

  .page-header h1 { font-size: 2rem; }
  .footer-bottom { flex-direction: column; text-align: center; }
}

@media (max-width: 480px) {
  .container { padding: 0 16px; }
  .hero h1 { font-size: 1.8rem; }
  .stats-grid { grid-template-columns: 1fr; }
  .process-steps { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .hero-buttons { flex-direction: column; }
  .hero-buttons .btn { width: 100%; justify-content: center; }
}