/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}
body {
  font-family: 'Inter', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;
  font-weight: 400;
  font-size: 1rem;
  line-height: 1.6;
  color: #E0E6F0;
  background-color: #0A0F1A;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
ul, ol { list-style: none; }
a {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease;
}
img, svg { display: block; max-width: 100%; }
button { font: inherit; cursor: pointer; border: none; background: none; color: inherit; }
:focus-visible {
  outline: 2px solid #00E5FF;
  outline-offset: 2px;
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ===== CSS Variables ===== */
:root {
  --color-primary: #003D6B;
  --color-primary-light: #005A9E;
  --color-primary-dark: #00203D;
  --color-accent-cyan: #00E5FF;
  --color-accent-orange: #FF6B35;
  --color-bg-dark: #0A0F1A;
  --color-bg-card: #141C2B;
  --color-bg-surface: #1A2638;
  --color-text-primary: #E0E6F0;
  --color-text-secondary: #8899B0;
  --color-border: #2A3A50;
  --color-success: #00E676;
  --color-warning: #FFAB00;
  --color-error: #FF5252;
  --font-headings: 'Poppins', 'PingFang SC', sans-serif;
  --font-body: 'Inter', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-numbers: 'JetBrains Mono', 'Consolas', monospace;
  --container-max: 1200px;
  --header-height: 64px;
}

/* ===== Skip Link ===== */
.skip-link {
  position: absolute;
  top: -100%;
  left: 1rem;
  z-index: 1000;
  padding: 0.5rem 1rem;
  background: var(--color-accent-cyan);
  color: #00203D;
  font-weight: 700;
  font-size: 0.875rem;
  border-radius: 0 0 4px 4px;
  transition: top 0.2s ease;
}
.skip-link:focus {
  top: 0;
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 900;
  background: linear-gradient(180deg, #0A0F1A 0%, #0D1422 100%);
  border-bottom: 1px solid #1A2A3A;
  box-shadow: 0 1px 12px rgba(0, 0, 0, 0.5);
}
.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1.5rem;
  height: var(--header-height);
  position: relative;
  z-index: 2;
}
.header__grid-lines {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: repeating-linear-gradient(90deg, transparent 0, transparent 40px, rgba(0, 229, 255, 0.08) 40px, rgba(0, 229, 255, 0.08) 41px);
  pointer-events: none;
}
.header__brand {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  flex-shrink: 0;
}
.header__logo {
  font-family: var(--font-headings);
  font-weight: 700;
  font-size: 1.25rem;
  color: #E0E6F0;
  letter-spacing: 0.02em;
  transition: color 0.2s ease;
}
.header__logo:hover {
  color: var(--color-accent-cyan);
}
.header__tagline {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  font-weight: 300;
  letter-spacing: 0.08em;
  display: none;
}
@media (min-width: 640px) {
  .header__tagline {
    display: inline;
  }
}
.header__nav {
  display: flex;
  align-items: center;
}
.header__nav-list {
  display: flex;
  align-items: center;
  gap: 0;
}
.header__nav-link {
  display: block;
  padding: 0.5rem 0.9rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  letter-spacing: 0.03em;
  position: relative;
  white-space: nowrap;
  transition: color 0.2s ease;
}
.header__nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0.9rem;
  right: 0.9rem;
  height: 2px;
  background: var(--color-accent-cyan);
  transform: scaleX(0);
  transition: transform 0.25s ease;
}
.header__nav-link:hover,
.header__nav-link:focus-visible {
  color: var(--color-accent-cyan);
}
.header__nav-link[aria-current="page"] {
  color: #E0E6F0;
}
.header__nav-link[aria-current="page"]::after {
  transform: scaleX(1);
}
.header__toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  gap: 5px;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  transition: border-color 0.2s ease;
}
.header__toggle:hover {
  border-color: var(--color-accent-cyan);
}
.header__toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text-secondary);
  border-radius: 1px;
  transition: background 0.2s ease;
}
.header__toggle:hover .header__toggle-bar {
  background: var(--color-accent-cyan);
}

/* ===== Mobile Nav ===== */
@media (max-width: 767px) {
  .header__inner {
    padding: 0 1rem;
  }
  .header__toggle {
    display: flex;
  }
  .header__nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(10, 15, 26, 0.98);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    transform: translateX(100%);
    transition: transform 0.35s cubic-bezier(0.22, 1, 0.36, 1);
    z-index: 800;
    overflow-y: auto;
    padding: 1.5rem;
    border-top: 1px solid #1A2A3A;
  }
  .header__nav[data-open] {
    transform: translateX(0);
  }
  .header__nav-list {
    flex-direction: column;
    gap: 0.25rem;
    width: 100%;
  }
  .header__nav-link {
    font-size: 1.1rem;
    padding: 0.9rem 1rem;
    border-bottom: 1px solid rgba(42, 58, 80, 0.4);
    width: 100%;
  }
  .header__nav-link::after {
    display: none;
  }
  .header__nav-link[aria-current="page"] {
    color: var(--color-accent-cyan);
    background: rgba(0, 229, 255, 0.06);
    border-left: 3px solid var(--color-accent-cyan);
    padding-left: calc(1rem - 3px);
  }
}
@media (min-width: 768px) {
  .header__nav {
    display: flex !important;
    transform: none !important;
    position: static;
    background: none;
    backdrop-filter: none;
    padding: 0;
    border: none;
    overflow: visible;
  }
  .header__nav[data-open] {
    transform: none;
  }
  .header__nav-list {
    flex-direction: row;
  }
  .header__nav-link {
    padding: 0.5rem 1rem;
  }
}

/* ===== Footer ===== */
.footer {
  background: linear-gradient(0deg, #060A12 0%, #0A0F1A 100%);
  border-top: 1px solid #1A2A3A;
  padding: 3rem 1.5rem 1.5rem;
  position: relative;
}
.footer__inner {
  max-width: var(--container-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}
@media (min-width: 640px) {
  .footer__inner {
    grid-template-columns: 1fr 1fr;
  }
}
@media (min-width: 1024px) {
  .footer__inner {
    grid-template-columns: 1.5fr 1fr 1.5fr;
    gap: 2rem;
  }
}
.footer__brand {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}
.footer__logo {
  font-family: var(--font-headings);
  font-weight: 700;
  font-size: 1.25rem;
  color: #E0E6F0;
  letter-spacing: 0.02em;
  transition: color 0.2s ease;
}
.footer__logo:hover {
  color: var(--color-accent-cyan);
}
.footer__tagline {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  font-weight: 300;
  letter-spacing: 0.06em;
}
.footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: 1.25rem;
  align-items: center;
}
.footer__link {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  font-weight: 400;
  letter-spacing: 0.02em;
  transition: color 0.2s ease;
  position: relative;
}
.footer__link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--color-accent-cyan);
  transform: scaleX(0);
  transition: transform 0.25s ease;
}
.footer__link:hover,
.footer__link:focus-visible {
  color: var(--color-accent-cyan);
}
.footer__link:hover::after,
.footer__link:focus-visible::after {
  transform: scaleX(1);
}
.footer__contact {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.footer__contact-item {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  font-weight: 300;
  letter-spacing: 0.02em;
}
.footer__icp {
  grid-column: 1 / -1;
  font-size: 0.7rem;
  color: rgba(136, 153, 176, 0.5);
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(42, 58, 80, 0.3);
  margin-top: 0.5rem;
  letter-spacing: 0.04em;
}

/* ===== Scroll Top Button ===== */
.scroll-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  z-index: 950;
  width: 44px;
  height: 44px;
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-secondary);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.4);
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.35s ease, transform 0.35s ease, visibility 0.35s ease, border-color 0.2s ease, color 0.2s ease;
}
.scroll-top[data-visible] {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.scroll-top:hover,
.scroll-top:focus-visible {
  border-color: var(--color-accent-cyan);
  color: var(--color-accent-cyan);
  background: rgba(0, 229, 255, 0.08);
}

/* ===== Utility: Container ===== */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.6rem 1.5rem;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.9rem;
  border-radius: 4px;
  border: 1px solid transparent;
  transition: all 0.2s ease;
  letter-spacing: 0.02em;
}
.btn--primary {
  background: var(--color-accent-cyan);
  color: #00203D;
  border-color: var(--color-accent-cyan);
}
.btn--primary:hover {
  background: transparent;
  color: var(--color-accent-cyan);
  box-shadow: 0 0 20px rgba(0, 229, 255, 0.15);
}
.btn--outline {
  background: transparent;
  color: var(--color-accent-cyan);
  border-color: var(--color-accent-cyan);
}
.btn--outline:hover {
  background: rgba(0, 229, 255, 0.08);
  box-shadow: 0 0 16px rgba(0, 229, 255, 0.1);
}

/* ===== Card ===== */
.card {
  background: var(--color-bg-card);
  border-radius: 8px;
  padding: 1.5rem;
  border: 1px solid var(--color-border);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.2);
  transition: border-color 0.25s ease, box-shadow 0.25s ease, transform 0.25s ease;
}
.card--glow {
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.2), 0 0 0 1px rgba(0, 229, 255, 0.05);
}
.card--glow:hover {
  border-color: rgba(0, 229, 255, 0.25);
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.3), 0 0 0 1px rgba(0, 229, 255, 0.15), 0 0 30px rgba(0, 229, 255, 0.05);
}

/* ===== Grid ===== */
.grid {
  display: grid;
  gap: 1.5rem;
}
.grid--2 {
  grid-template-columns: 1fr;
}
@media (min-width: 640px) {
  .grid--2 {
    grid-template-columns: 1fr 1fr;
  }
}
.grid--3 {
  grid-template-columns: 1fr;
}
@media (min-width: 640px) {
  .grid--3 {
    grid-template-columns: 1fr 1fr;
  }
}
@media (min-width: 1024px) {
  .grid--3 {
    grid-template-columns: 1fr 1fr 1fr;
  }
}

/* ===== Section ===== */
.section {
  padding: 4rem 0;
}
.section__title {
  font-family: var(--font-headings);
  font-weight: 700;
  font-size: 1.75rem;
  color: #E0E6F0;
  margin-bottom: 1.5rem;
  letter-spacing: 0.01em;
  position: relative;
}
.section__title::before {
  content: '//';
  color: var(--color-accent-cyan);
  margin-right: 0.5rem;
  font-weight: 300;
  opacity: 0.6;
}

/* ===== Tag ===== */
.tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 500;
  padding: 0.2rem 0.6rem;
  border: 1px solid rgba(0, 229, 255, 0.3);
  border-radius: 2px;
  color: var(--color-accent-cyan);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ===== Data Number ===== */
.data-number {
  font-family: var(--font-numbers);
  font-weight: 400;
  color: var(--color-accent-cyan);
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem 0.6rem;
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  padding: 1rem 0;
}
.breadcrumb__link {
  color: var(--color-text-secondary);
  transition: color 0.2s ease;
}
.breadcrumb__link:hover {
  color: var(--color-accent-cyan);
}
.breadcrumb__item[aria-current="page"] {
  color: var(--color-text-primary);
}
.breadcrumb__separator {
  color: rgba(136, 153, 176, 0.3);
  font-size: 0.7rem;
}

/* ===== Responsive Fine-tune ===== */
@media (max-width: 480px) {
  .header__logo {
    font-size: 1.05rem;
  }
  .footer {
    padding: 2rem 1rem 1rem;
  }
  .scroll-top {
    bottom: 1.25rem;
    right: 1.25rem;
    width: 40px;
    height: 40px;
  }
}
@media (min-width: 768px) and (max-width: 1023px) {
  .footer__inner {
    grid-template-columns: 1fr 1fr;
  }
}