:root {
  --bg-main: #070a13;
  --bg-card: rgba(15, 23, 42, 0.7);
  --bg-card-hover: rgba(30, 41, 59, 0.85);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(56, 189, 248, 0.35);
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  --accent-cyan: #38bdf8;
  --accent-purple: #a855f7;
  --accent-emerald: #10b981;
  --glow-cyan: rgba(56, 189, 248, 0.25);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Inter', 'Noto Sans JP', -apple-system, sans-serif;
  background-color: var(--bg-main);
  color: var(--text-main);
  line-height: 1.7;
  overflow-x: hidden;
  background-image: 
    radial-gradient(circle at 15% 20%, rgba(56, 189, 248, 0.08) 0%, transparent 40%),
    radial-gradient(circle at 85% 60%, rgba(168, 85, 247, 0.08) 0%, transparent 40%),
    linear-gradient(to right, rgba(255, 255, 255, 0.02) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.02) 1px, transparent 1px);
  background-size: 100% 100%, 100% 100%, 60px 60px, 60px 60px;
}

a {
  color: inherit;
  text-decoration: none;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Navigation */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(16px);
  background: rgba(7, 10, 19, 0.8);
  border-bottom: 1px solid var(--border-color);
}
.nav-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 72px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: 'Outfit', sans-serif;
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.5px;
}
.logo-badge {
  font-size: 10px;
  padding: 2px 8px;
  border-radius: 12px;
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent-cyan);
  border: 1px solid rgba(56, 189, 248, 0.3);
  font-weight: 600;
  text-transform: uppercase;
}
.nav-links {
  display: flex;
  gap: 28px;
  align-items: center;
  font-size: 14px;
  color: var(--text-muted);
}
.nav-links a:hover {
  color: var(--text-main);
  transition: color 0.2s;
}
.btn-nav {
  background: linear-gradient(135deg, #0284c7 0%, #2563eb 100%);
  color: #fff !important;
  padding: 8px 18px;
  border-radius: 20px;
  font-weight: 600;
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
  transition: transform 0.2s, box-shadow 0.2s;
}
.btn-nav:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

/* Hero */
.hero {
  padding: 100px 0 80px;
  text-align: center;
}
.status-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(16, 185, 129, 0.1);
  border: 1px solid rgba(16, 185, 129, 0.3);
  padding: 6px 16px;
  border-radius: 30px;
  font-size: 12.5px;
  color: #34d399;
  margin-bottom: 28px;
  font-weight: 500;
}
.status-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: var(--accent-emerald);
  box-shadow: 0 0 10px var(--accent-emerald);
}
.hero h1 {
  font-family: 'Outfit', 'Noto Sans JP', sans-serif;
  font-size: clamp(32px, 5vw, 54px);
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: -1px;
  margin-bottom: 24px;
  background: linear-gradient(135deg, #ffffff 0%, #cbd5e1 50%, #94a3b8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero p {
  font-size: clamp(16px, 2vw, 18px);
  color: var(--text-muted);
  max-width: 680px;
  margin: 0 auto 40px;
  line-height: 1.8;
}
.hero-cta {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: linear-gradient(135deg, var(--accent-cyan) 0%, #2563eb 100%);
  color: #ffffff;
  padding: 14px 28px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 15px;
  box-shadow: 0 8px 24px rgba(56, 189, 248, 0.25);
  transition: all 0.25s;
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 30px rgba(56, 189, 248, 0.4);
}
.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: rgba(30, 41, 59, 0.6);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 14px 28px;
  border-radius: 12px;
  font-weight: 600;
  font-size: 15px;
  backdrop-filter: blur(10px);
  transition: all 0.25s;
}
.btn-secondary:hover {
  background: rgba(51, 65, 85, 0.8);
  border-color: rgba(255, 255, 255, 0.2);
  transform: translateY(-2px);
}

/* Section Common */
section {
  padding: 80px 0;
}
.section-header {
  margin-bottom: 48px;
  text-align: center;
}
.section-tag {
  font-family: 'Outfit', sans-serif;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--accent-cyan);
  margin-bottom: 8px;
  display: block;
}
.section-title {
  font-family: 'Outfit', 'Noto Sans JP', sans-serif;
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.5px;
}

/* Core Research Cards */
.grid-2x2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 32px 28px;
  backdrop-filter: blur(16px);
  transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
  position: relative;
  overflow: hidden;
}
.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--border-hover), transparent);
  opacity: 0;
  transition: opacity 0.3s;
}
.card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-hover);
  transform: translateY(-4px);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.4);
}
.card:hover::before {
  opacity: 1;
}
.card-icon {
  font-size: 32px;
  margin-bottom: 20px;
  display: inline-block;
}
.card-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-main);
}
.card-desc {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.7;
}

/* Tech Stack */
.stack-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
  max-width: 800px;
  margin: 0 auto;
}
.stack-pill {
  background: rgba(30, 41, 59, 0.5);
  border: 1px solid var(--border-color);
  padding: 8px 18px;
  border-radius: 10px;
  font-size: 13.5px;
  font-weight: 500;
  color: #cbd5e1;
}

/* Footer */
footer {
  border-top: 1px solid var(--border-color);
  padding: 50px 0 30px;
  text-align: center;
  font-size: 13.5px;
  color: var(--text-muted);
}
.footer-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 20px;
}
.footer-links a:hover {
  color: var(--text-main);
}
.copyright {
  font-size: 12px;
  color: #64748b;
}

/* Articles & Categories Feed */
.section-subtitle {
  font-size: 15px;
  color: var(--text-muted);
  max-width: 600px;
  margin: 12px auto 0;
  line-height: 1.6;
}

.category-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
  margin-bottom: 40px;
}
.category-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(30, 41, 59, 0.6);
  border: 1px solid var(--border-color);
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  font-family: inherit;
  color: #cbd5e1;
  cursor: pointer;
  outline: none;
  user-select: none;
  transition: all 0.25s;
}
.category-pill:hover,
.category-pill.active {
  background: rgba(56, 189, 248, 0.15);
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
  transform: translateY(-1px);
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 28px;
  margin-bottom: 48px;
}

.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  overflow: hidden;
  backdrop-filter: blur(16px);
  display: flex;
  flex-direction: column;
  transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
  text-decoration: none;
  color: inherit;
}
.article-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-cyan);
  transform: translateY(-4px);
  box-shadow: 0 14px 36px rgba(0, 0, 0, 0.5), 0 0 20px rgba(56, 189, 248, 0.15);
}

.article-thumb-wrap {
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: #0f172a;
  position: relative;
}
.article-thumb {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.4s ease;
}
.article-card:hover .article-thumb {
  transform: scale(1.05);
}

.article-body {
  padding: 24px;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}
.article-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
  font-size: 12px;
}
.article-category {
  padding: 3px 10px;
  border-radius: 6px;
  background: rgba(56, 189, 248, 0.12);
  color: var(--accent-cyan);
  font-weight: 600;
}
.article-date {
  color: var(--text-muted);
}
.article-title {
  font-size: 17px;
  font-weight: 700;
  line-height: 1.5;
  margin-bottom: 12px;
  color: var(--text-main);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.article-excerpt {
  font-size: 13.5px;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 20px;
  flex-grow: 1;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.article-readmore {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 700;
  color: var(--accent-cyan);
  margin-top: auto;
}

.articles-footer {
  text-align: center;
}

/* Skeleton Loading */
.skeleton-card {
  background: rgba(15, 23, 42, 0.5);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  overflow: hidden;
}
.skeleton-thumb {
  width: 100%;
  aspect-ratio: 16 / 9;
  background: linear-gradient(90deg, #1e293b 25%, #334155 50%, #1e293b 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
}
.skeleton-body {
  padding: 24px;
}
.skeleton-line {
  height: 14px;
  border-radius: 4px;
  background: linear-gradient(90deg, #1e293b 25%, #334155 50%, #1e293b 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  margin-bottom: 12px;
}
.skeleton-line.short {
  width: 40%;
}
.skeleton-line.medium {
  width: 70%;
}
@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

@media (max-width: 768px) {
  .nav-links {
    display: none;
  }
  .hero {
    padding: 60px 0 50px;
  }
  .articles-grid {
    grid-template-columns: 1fr;
  }
}