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

/* CSS Variables */
:root {
  --color-primary-bg: #0B1E36;
  --color-primary-accent: #FF6B35;
  --color-secondary-accent: #39FF14;
  --color-text-primary: #FFFFFF;
  --color-text-secondary: #B0BEC5;
  --color-card-bg: #132A45;
  --color-border: #2A4A6A;
  --color-overlay: #0B1E36CC;

  --font-heading: 'Montserrat', 'Helvetica Neue', 'Arial Black', sans-serif;
  --font-body: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;

  --container-max: 1200px;
  --gap: 1.5rem;
}

/* Accessibility */
.skip-link {
  position: absolute;
  top: -100%;
  left: 0;
  padding: 0.5rem 1rem;
  background: var(--color-primary-accent);
  color: #000;
  z-index: 1000;
  font-weight: 700;
  transition: top 0.2s;
}
.skip-link:focus {
  top: 0;
}

/* Base */
html {
  scroll-behavior: smooth;
  font-size: 16px;
}
body {
  background-color: var(--color-primary-bg);
  color: var(--color-text-primary);
  font-family: var(--font-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* Container */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1rem;
}

/* Typography */
h1, h2, h3, h4, h5 {
  font-family: var(--font-heading);
  font-weight: 900;
  letter-spacing: -0.02em;
  color: var(--color-text-primary);
}
h1 { font-size: clamp(2.5rem, 6vw, 4rem); }
h2 { font-size: clamp(1.8rem, 4vw, 2.8rem); }
h3 { font-size: clamp(1.3rem, 2.5vw, 2rem); }
p { margin-bottom: 1rem; }
a {
  color: var(--color-primary-accent);
  text-decoration: none;
  transition: color 0.2s;
}
a:hover { color: var(--color-secondary-accent); }
a:focus-visible { outline: 2px solid var(--color-primary-accent); outline-offset: 2px; }

/* Header */
.site-header {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: transparent;
  padding: 0.8rem 0;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-heading);
  font-weight: 900;
  font-size: 1.5rem;
  color: var(--color-text-primary);
  text-decoration: none;
}
.brand-icon {
  display: inline-block;
  width: 32px;
  height: 32px;
  background: var(--color-primary-accent);
  clip-path: polygon(0% 50%, 50% 0%, 100% 50%, 50% 100%);
}
.brand-text { letter-spacing: -0.02em; }
.nav-toggle {
  display: none;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  flex-direction: column;
  gap: 4px;
}
.nav-toggle-line {
  display: block;
  width: 24px;
  height: 3px;
  background: var(--color-text-primary);
  transition: transform 0.3s, opacity 0.3s;
}
.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }
.nav-list {
  display: flex;
  list-style: none;
  gap: 1.5rem;
  align-items: center;
}
.nav-item a {
  font-family: var(--font-body);
  font-weight: 600;
  color: var(--color-text-primary);
  text-decoration: none;
  padding: 0.25rem 0;
  position: relative;
  transition: color 0.2s;
}
.nav-item a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0%;
  height: 2px;
  background: var(--color-primary-accent);
  transition: width 0.3s;
}
.nav-item a:hover::after { width: 100%; }
.nav-item a[aria-current="page"] {
  color: var(--color-primary-accent);
}
.nav-item a[aria-current="page"]::after { width: 100%; background: var(--color-primary-accent); }

/* Footer */
.site-footer {
  background: var(--color-card-background);
  padding: 3rem 0 2rem;
  margin-top: 4rem;
  border-top: 1px solid var(--color-border);
}
.footer-columns {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 2rem;
  margin-bottom: 2rem;
}
.footer-col h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-primary-accent);
  margin-bottom: 0.8rem;
}
.footer-col ul {
  list-style: none;
}
.footer-col li { margin-bottom: 0.4rem; }
.footer-col a {
  color: var(--color-text-secondary);
  font-size: 0.9rem;
}
.footer-col a:hover { color: var(--color-text-primary); }
.footer-trust {
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 0.8rem;
  padding: 1rem 0;
  border-top: 1px solid var(--color-border);
  margin-top: 2rem;
}
.footer-meta {
  text-align: center;
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  margin-top: 1rem;
}
.footer-meta a { color: var(--color-text-secondary); margin: 0 0.3rem; }
.footer-meta a:hover { color: var(--color-text-primary); }
.footer-contact { margin-bottom: 0.4rem; }
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--color-primary-accent);
  color: #000;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.3s, transform 0.3s;
  z-index: 900;
}
.back-to-top.visible { opacity: 1; transform: translateY(0); }
.back-to-top:focus-visible { outline: 2px solid var(--color-secondary-accent); }

/* Common components */
.page-section {
  padding: 2rem 0;
}
.card {
  background: var(--color-card-bg);
  border-radius: 8px;
  padding: 1.5rem;
  border: 1px solid var(--color-border);
  transition: transform 0.2s, box-shadow 0.2s;
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.4);
}
.btn {
  display: inline-block;
  background: var(--color-primary-accent);
  color: #000;
  font-weight: 700;
  padding: 0.6rem 1.5rem;
  border-radius: 4px;
  border: none;
  cursor: pointer;
  font-family: var(--font-body);
  transition: background 0.2s, transform 0.2s;
}
.btn:hover { background: var(--color-secondary-accent); transform: scale(1.02); }
.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--color-primary-accent);
  color: #000;
}
/* Frame border (box view) */
.frame {
  position: relative;
  border: 2px solid var(--color-border);
  padding: 2rem;
  background: var(--color-overlay);
}
.frame::before, .frame::after {
  content: '';
  position: absolute;
  width: 30px;
  height: 30px;
  border: 2px solid var(--color-primary-accent);
}
.frame::before { top: -2px; left: -2px; border-right: none; border-bottom: none; }
.frame::after { bottom: -2px; right: -2px; border-left: none; border-top: none; }

/* Divider tilt */
.divider-tilt {
  position: relative;
  height: 4px;
  background: transparent;
  overflow: hidden;
  margin: 2rem 0;
}
.divider-tilt::before {
  content: '';
  position: absolute;
  left: -50%;
  width: 200%;
  height: 100%;
  background: linear-gradient(135deg, var(--color-primary-accent) 25%, transparent 50%);
  transform: skewX(-20deg);
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition-duration: 0.01ms !important; animation-duration: 0.01ms !important; }
  html { scroll-behavior: auto; }
}

/* Responsive */
@media (max-width: 768px) {
  .header-inner { position: relative; }
  .nav-toggle { display: flex; }
  .nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--color-primary-bg);
    border-bottom: 2px solid var(--color-border);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s;
  }
  .nav[data-open] { max-height: 400px; }
  .nav-list {
    flex-direction: column;
    padding: 1rem;
    gap: 0.8rem;
  }
  .footer-columns { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 480px) {
  .footer-columns { grid-template-columns: 1fr; }
  .brand { font-size: 1.2rem; }
}