* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #0b1120;
  color: #e5e7eb;
}

a {
  color: #38bdf8;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

header {
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(16px);
  background: rgba(15, 23, 42, 0.9);
  border-bottom: 1px solid rgba(148, 163, 184, 0.4);
}

.nav-shell {
  max-width: 960px;
  margin: 0 auto;
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.brand-icon {
  width: 28px;
  height: 28px;
  border-radius: 999px;
  background: radial-gradient(circle at 30% 20%, #4ade80, #22c55e, #16a34a);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #0b1120;
  font-weight: 700;
  font-size: 0.9rem;
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}

.brand-title {
  font-weight: 700;
  font-size: 0.95rem;
}

.brand-sub {
  font-size: 0.7rem;
  color: #9ca3af;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.8rem;
}

.nav-links a {
  padding: 0.25rem 0.5rem;
  border-radius: 999px;
  border: 1px solid transparent;
}

.nav-links a.active,
.nav-links a:hover {
  border-color: rgba(148, 163, 184, 0.7);
  background: rgba(15, 23, 42, 0.9);
}

.nav-toggle {
  display: none;
}

main {
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem;
}

.hero {
  margin-top: 0.75rem;
  padding: 1rem;
  border-radius: 1.25rem;
  border: 1px solid rgba(148, 163, 184, 0.5);
  background: radial-gradient(circle at 0% 0%, rgba(45, 212, 191, 0.18), transparent 55%),
              radial-gradient(circle at 100% 0%, rgba(56, 189, 248, 0.22), transparent 60%),
              rgba(15, 23, 42, 0.96);
}

.hero-kicker {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: #a5b4fc;
  margin-bottom: 0.35rem;
}

.hero-title {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
}

.hero-subtitle {
  font-size: 0.9rem;
  color: #cbd5f5;
  max-width: 40rem;
}

.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin-top: 0.6rem;
}

.tag-pill {
  font-size: 0.7rem;
  border-radius: 999px;
  padding: 0.15rem 0.55rem;
  border: 1px solid rgba(148, 163, 184, 0.6);
  background: rgba(15, 23, 42, 0.9);
}

.section {
  margin-top: 1.25rem;
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.5rem;
}

.section-title {
  font-size: 0.95rem;
  font-weight: 600;
}

.section-subtitle {
  font-size: 0.75rem;
  color: #9ca3af;
}

.card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
}

.card {
  border-radius: 1rem;
  border: 1px solid rgba(55, 65, 81, 0.9);
  background: radial-gradient(circle at 0% 0%, rgba(52, 211, 153, 0.08), transparent 55%),
              rgba(15, 23, 42, 0.98);
  padding: 0.75rem 0.85rem;
}

.card-title-row {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 0.5rem;
}

.card-title {
  font-size: 0.9rem;
  font-weight: 600;
}

.card-meta {
  font-size: 0.7rem;
  color: #9ca3af;
}

.card-pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
  margin-top: 0.35rem;
}

.small-pill {
  font-size: 0.65rem;
  border-radius: 999px;
  padding: 0.05rem 0.45rem;
  border: 1px solid rgba(55, 65, 81, 0.95);
  color: #d1d5db;
}

.card-body {
  margin-top: 0.4rem;
  font-size: 0.8rem;
  color: #e5e7eb;
}

.card-footer {
  margin-top: 0.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.7rem;
  color: #9ca3af;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  border-radius: 999px;
  padding: 0.3rem 0.7rem;
  font-size: 0.75rem;
  border: 1px solid rgba(148, 163, 184, 0.7);
  background: rgba(15, 23, 42, 0.98);
}

.btn span.icon {
  font-size: 0.9rem;
}

.search-shell {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.4rem;
}

.search-input-wrap {
  flex: 1 1 160px;
  position: relative;
}

.search-input-wrap input {
  width: 100%;
  padding: 0.4rem 0.65rem 0.4rem 1.6rem;
  border-radius: 999px;
  border: 1px solid rgba(55, 65, 81, 0.9);
  background: rgba(15, 23, 42, 0.96);
  color: #e5e7eb;
  font-size: 0.8rem;
}

.search-input-wrap input::placeholder {
  color: #6b7280;
}

.search-icon {
  position: absolute;
  left: 0.55rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.8rem;
  color: #6b7280;
}

.select-wrap {
  flex: 0 0 140px;
}

.select-wrap select {
  width: 100%;
  padding: 0.4rem 0.65rem;
  border-radius: 999px;
  border: 1px solid rgba(55, 65, 81, 0.9);
  background: rgba(15, 23, 42, 0.96);
  color: #e5e7eb;
  font-size: 0.8rem;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  font-size: 0.65rem;
  border: 1px solid rgba(55, 65, 81, 0.9);
  color: #9ca3af;
}

.breadcrumb {
  font-size: 0.7rem;
  color: #9ca3af;
  margin: 0.4rem 0 0.75rem;
}

.breadcrumb a {
  color: #9ca3af;
}

.breadcrumb span {
  color: #6b7280;
}

.topic-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.7fr);
  gap: 1rem;
}

.topic-main {
  padding: 0.85rem;
  border-radius: 1rem;
  border: 1px solid rgba(55, 65, 81, 0.9);
  background: radial-gradient(circle at 0% 0%, rgba(52, 211, 153, 0.08), transparent 55%),
              rgba(15, 23, 42, 0.98);
}

.topic-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.topic-kicker {
  font-size: 0.75rem;
  color: #a5b4fc;
  margin-bottom: 0.45rem;
}

.topic-meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin-bottom: 0.5rem;
}

.topic-section {
  margin-top: 0.75rem;
}

.topic-section h2 {
  font-size: 0.9rem;
  margin-bottom: 0.3rem;
}

.topic-section p,
.topic-section ul {
  font-size: 0.8rem;
  color: #e5e7eb;
}

.topic-section ul {
  margin: 0.3rem 0 0.1rem 1.1rem;
  padding: 0;
}

.topic-aside {
  padding: 0.85rem;
  border-radius: 1rem;
  border: 1px dashed rgba(55, 65, 81, 0.9);
  background: radial-gradient(circle at 100% 0%, rgba(56, 189, 248, 0.12), transparent 60%),
              rgba(15, 23, 42, 0.98);
  font-size: 0.75rem;
  color: #e5e7eb;
}

.aside-title {
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.video-list {
  list-style: none;
  padding: 0;
  margin: 0.35rem 0 0;
}

.video-list li {
  margin-bottom: 0.25rem;
}

.video-list a {
  font-size: 0.76rem;
}

footer {
  max-width: 960px;
  margin: 0 auto;
  padding: 0.75rem 1rem 1.25rem;
  font-size: 0.7rem;
  color: #6b7280;
}

/* Mobile nav */
@media (max-width: 640px) {
  .nav-links {
    display: none;
  }
  .nav-links.open {
    display: flex;
    position: absolute;
    top: 48px;
    right: 0.75rem;
    flex-direction: column;
    align-items: flex-start;
    padding: 0.5rem;
    border-radius: 0.75rem;
    background: rgba(15, 23, 42, 0.98);
    border: 1px solid rgba(55, 65, 81, 0.9);
  }
  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    border-radius: 999px;
    border: 1px solid rgba(55, 65, 81, 0.9);
    background: rgba(15, 23, 42, 0.96);
    font-size: 0.85rem;
    cursor: pointer;
  }
}

@media (min-width: 720px) {
  .card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .topic-layout {
    grid-template-columns: minmax(0, 2.1fr) minmax(0, 1.2fr);
  }
}