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

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

body {
  font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI',
    'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  line-height: 1.8;
  color: #1a1a2e;
  background-color: #ffffff;
}

/* ===== Utils ===== */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 28px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ===== Links ===== */
a {
  color: #0d9488;
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: #0f766e;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  background: #f9fafb;
  border-bottom: 1px solid #e5e7eb;
  padding: 10px 0;
  font-size: 13px;
}

.breadcrumb ol {
  list-style: none;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
}

.breadcrumb li {
  color: #9ca3af;
  display: flex;
  align-items: center;
  gap: 6px;
}

.breadcrumb li:not(:last-child)::after {
  content: '\203A';
  color: #d1d5db;
  font-size: 16px;
}

.breadcrumb li a {
  color: #0d9488;
}

.breadcrumb li a:hover {
  color: #0f766e;
  text-decoration: underline;
}

.breadcrumb li[aria-current='page'] {
  color: #6b7280;
  font-weight: 500;
}

/* ===== Header ===== */
header {
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid #f3f4f6;
  position: sticky;
  top: 0;
  z-index: 100;
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 0;
  gap: 16px;
}

.logo {
  font-size: 22px;
  font-weight: 700;
  color: #0d9488;
  letter-spacing: -0.3px;
  white-space: nowrap;
  transition: opacity 0.2s ease;
}

.logo:hover {
  opacity: 0.8;
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 2px;
  list-style: none;
}

.nav-links a {
  display: inline-block;
  font-size: 14px;
  font-weight: 500;
  color: #6b7280;
  padding: 6px 12px;
  border-radius: 6px;
  transition: all 0.2s ease;
}

.nav-links a:hover {
  color: #0d9488;
  background: #f0fdfa;
  text-decoration: none;
}

/* ===== Hero ===== */
.hero {
  background: linear-gradient(180deg, #f0fdfa 0%, #ffffff 100%);
  padding: 80px 0 72px;
  text-align: center;
}

.hero h1 {
  font-size: 44px;
  font-weight: 800;
  margin-bottom: 16px;
  line-height: 1.3;
  letter-spacing: -0.5px;
  color: #111827;
}

.hero h1 span {
  color: #0d9488;
}

.hero-subtitle {
  font-size: 17px;
  margin-bottom: 36px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.75;
  color: #6b7280;
}

.hero-cta {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  padding: 13px 32px;
  font-size: 15px;
  font-weight: 600;
  border-radius: 8px;
  border: none;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.25s ease;
  letter-spacing: 0.2px;
}

.btn-primary {
  background: #0d9488;
  color: #ffffff;
  box-shadow: 0 2px 8px rgba(13, 148, 136, 0.25);
}

.btn-primary:hover {
  background: #0f766e;
  box-shadow: 0 4px 16px rgba(13, 148, 136, 0.35);
  transform: translateY(-1px);
  text-decoration: none;
  color: #ffffff;
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: #ffffff;
  color: #0d9488;
  border: 2px solid #ccfbf1;
}

.btn-secondary:hover {
  background: #f0fdfa;
  border-color: #0d9488;
  transform: translateY(-1px);
  text-decoration: none;
  color: #0f766e;
}

.btn-secondary:active {
  transform: translateY(0);
}

/* ===== Quick Nav ===== */
.quick-nav-section {
  padding: 64px 0;
  background: #ffffff;
}

.quick-nav {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 20px;
}

.nav-card {
  background: #ffffff;
  padding: 32px 26px;
  border-radius: 12px;
  text-align: center;
  transition: all 0.3s ease;
  border: 1px solid #f3f4f6;
  cursor: default;
}

.nav-card:hover {
  border-color: #ccfbf1;
  box-shadow: 0 4px 24px rgba(13, 148, 136, 0.08);
  transform: translateY(-3px);
}

.nav-card-icon {
  font-size: 32px;
  display: block;
  margin-bottom: 12px;
}

.nav-card h3 {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 6px;
  color: #111827;
}

.nav-card p {
  font-size: 13px;
  color: #9ca3af;
  line-height: 1.6;
}

/* ===== Section Titles ===== */
.section-tag {
  font-size: 12px;
  color: #0d9488;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 8px;
  text-align: center;
}

.section-title {
  font-size: 34px;
  font-weight: 700;
  margin-bottom: 14px;
  text-align: center;
  color: #111827;
  letter-spacing: -0.3px;
}

.section-desc {
  font-size: 15px;
  color: #6b7280;
  text-align: center;
  max-width: 640px;
  margin: 0 auto 52px;
  line-height: 1.7;
}

/* ===== Blockchain Basics ===== */
.basics-section {
  padding: 80px 0;
  background: #f9fafb;
}

.basics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.basics-card {
  background: #ffffff;
  padding: 30px 28px;
  border-radius: 12px;
  border: 1px solid #f3f4f6;
  transition: all 0.3s ease;
}

.basics-card:hover {
  border-color: #ccfbf1;
  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.04);
}

.basics-card h3 {
  font-size: 19px;
  font-weight: 600;
  margin-bottom: 10px;
  color: #111827;
}

.basics-card h3 .accent {
  color: #0d9488;
}

.basics-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.75;
}

/* ===== Bitcoin Technical ===== */
.technical-section {
  padding: 80px 0;
  background: #ffffff;
}

.tech-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.tech-item {
  display: flex;
  gap: 18px;
  align-items: flex-start;
  padding: 24px;
  background: #f9fafb;
  border-radius: 12px;
  border: 1px solid #f3f4f6;
  transition: all 0.3s ease;
}

.tech-item:hover {
  background: #f0fdfa;
  border-color: #ccfbf1;
}

.tech-num {
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #0d9488;
  color: #ffffff;
  border-radius: 10px;
  font-size: 18px;
  font-weight: 700;
}

.tech-body h3 {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 6px;
  color: #111827;
}

.tech-body p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.75;
}

/* ===== Mining Section ===== */
.mining-section {
  padding: 80px 0;
  background: #f9fafb;
}

.mining-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 24px;
}

.mining-card {
  background: #ffffff;
  padding: 28px 24px;
  border-radius: 12px;
  border: 1px solid #f3f4f6;
  transition: all 0.3s ease;
}

.mining-card:hover {
  border-color: #ccfbf1;
  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.04);
}

.mining-card .icon {
  font-size: 28px;
  margin-bottom: 12px;
  display: block;
}

.mining-card h3 {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 8px;
  color: #111827;
}

.mining-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.7;
}

/* ===== Wallet Section ===== */
.wallet-section {
  padding: 80px 0;
  background: #ffffff;
}

.wallet-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}

.wallet-card {
  background: #f9fafb;
  padding: 30px 28px;
  border-radius: 12px;
  border: 1px solid #f3f4f6;
  transition: all 0.3s ease;
  border-top: 3px solid transparent;
}

.wallet-card:hover {
  background: #ffffff;
  border-color: #ccfbf1;
  border-top-color: #0d9488;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.04);
}

.wallet-card h3 {
  font-size: 19px;
  font-weight: 600;
  margin-bottom: 10px;
  color: #111827;
}

.wallet-card .wallet-tag {
  display: inline-block;
  padding: 3px 12px;
  background: #f0fdfa;
  color: #0d9488;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  margin-bottom: 12px;
}

.wallet-card p {
  font-size: 14px;
  color: #6b7280;
  line-height: 1.75;
}

/* ===== FAQ ===== */
.faq-section {
  padding: 80px 0;
  background: #f9fafb;
}

.faq-container {
  max-width: 780px;
  margin: 0 auto;
}

.faq-item {
  margin-bottom: 10px;
  border: 1px solid #f3f4f6;
  border-radius: 10px;
  overflow: hidden;
  background: #ffffff;
  transition: all 0.25s ease;
}

.faq-item:hover {
  border-color: #ccfbf1;
}

.faq-question {
  padding: 18px 22px;
  background: #ffffff;
  cursor: pointer;
  font-weight: 600;
  font-size: 15px;
  color: #111827;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: all 0.2s ease;
  user-select: none;
  outline: none;
}

.faq-question:focus-visible {
  box-shadow: inset 0 0 0 2px #0d9488;
}

.faq-question:hover {
  background: #f0fdfa;
  color: #0d9488;
}

.faq-toggle {
  font-size: 18px;
  transition: transform 0.3s ease;
  color: #d1d5db;
  flex-shrink: 0;
  margin-left: 14px;
  font-weight: 400;
}

.faq-item.active .faq-toggle {
  transform: rotate(45deg);
  color: #0d9488;
}

.faq-item.active .faq-question {
  background: #f0fdfa;
  color: #0d9488;
}

.faq-answer {
  padding: 0 22px;
  max-height: 0;
  overflow: hidden;
  color: #6b7280;
  font-size: 14px;
  line-height: 1.75;
  transition: all 0.35s ease;
}

.faq-answer p {
  padding: 18px 0;
}

.faq-item.active .faq-answer {
  max-height: 600px;
}

/* ===== Footer ===== */
footer {
  background: #111827;
  color: #9ca3af;
  padding: 60px 0 20px;
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 40px;
  margin-bottom: 40px;
}

.footer-section h4 {
  color: #ffffff;
  margin-bottom: 16px;
  font-size: 15px;
  font-weight: 600;
}

.footer-section p {
  font-size: 13px;
  line-height: 1.7;
  color: #6b7280;
}

.footer-section ul {
  list-style: none;
}

.footer-section li {
  margin-bottom: 8px;
}

.footer-section a {
  color: #6b7280;
  font-size: 13px;
  transition: color 0.2s ease;
}

.footer-section a:hover {
  color: #0d9488;
  text-decoration: none;
}

.footer-bottom {
  border-top: 1px solid #1f2937;
  padding-top: 20px;
  text-align: center;
  font-size: 12px;
  color: #4b5563;
  line-height: 1.6;
}

/* ===== Scroll Animation ===== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}

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

/* ===== Responsive ===== */
@media (max-width: 1024px) {
  .hero h1 { font-size: 36px; }
  .section-title { font-size: 28px; }
}

@media (max-width: 768px) {
  .container { padding: 0 16px; }

  nav {
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
  }

  .logo { font-size: 18px; width: 100%; text-align: center; }

  .nav-links { gap: 0; flex-wrap: wrap; justify-content: center; }
  .nav-links a { font-size: 13px; padding: 5px 8px; }

  .hero { padding: 56px 0 48px; }
  .hero h1 { font-size: 28px; }
  .hero-subtitle { font-size: 15px; }

  .hero-cta { flex-direction: column; align-items: center; gap: 10px; }
  .btn { padding: 12px 24px; font-size: 14px; width: 100%; max-width: 280px; text-align: center; }

  .section-title { font-size: 24px; }
  .section-desc { font-size: 14px; margin-bottom: 36px; }

  .quick-nav { grid-template-columns: 1fr 1fr; gap: 14px; }

  .basics-grid { grid-template-columns: 1fr; }
  .mining-cards { grid-template-columns: 1fr 1fr; }
  .wallet-grid { grid-template-columns: 1fr; }

  .tech-item { flex-direction: column; gap: 10px; }

  .faq-question { padding: 14px 16px; font-size: 14px; }

  .footer-content { grid-template-columns: 1fr 1fr; gap: 28px; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 24px; }
  .section-title { font-size: 22px; }

  .quick-nav { grid-template-columns: 1fr; }
  .mining-cards { grid-template-columns: 1fr; }

  .footer-content { grid-template-columns: 1fr; gap: 24px; text-align: center; }
  .footer-section ul { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; }
  .footer-section li { margin-bottom: 0; }
}

@media print {
  header, .breadcrumb, footer, .hero-cta { display: none; }
  body { background: #ffffff; color: #000000; }
  .hero { background: none; color: #000000; padding: 20px 0; }
}