:root {
  --bg: #0f1419;
  --bg-elevated: #1a222c;
  --ink: #e8eef4;
  --muted: #8b9aab;
  --accent: #3d9a7a;
  --accent-soft: rgba(61, 154, 122, 0.16);
  --line: rgba(232, 238, 244, 0.1);
  --technical: #5b9fd4;
  --non-technical: #d4a05b;
  --radius: 14px;
  --font-sans: 'DM Sans', system-ui, sans-serif;
  --font-display: 'Instrument Serif', Georgia, serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
}

body {
  font-family: var(--font-sans);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.5;
}

.atmosphere {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(ellipse 80% 50% at 10% -10%, rgba(61, 154, 122, 0.22), transparent 55%),
    radial-gradient(ellipse 60% 40% at 90% 0%, rgba(91, 159, 212, 0.18), transparent 50%),
    radial-gradient(ellipse 50% 30% at 50% 100%, rgba(212, 160, 91, 0.08), transparent 45%),
    var(--bg);
}

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

.site-header {
  max-width: 1100px;
  margin: 0 auto;
  padding: 4.5rem 1.5rem 2rem;
}

.brand {
  margin: 0 0 0.35rem;
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}

.site-header h1 {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(2.6rem, 6vw, 4.2rem);
  font-weight: 400;
  letter-spacing: -0.02em;
  line-height: 1.05;
}

.lede {
  max-width: 36rem;
  margin: 1rem 0 0;
  color: var(--muted);
  font-size: 1.05rem;
}

kbd {
  display: inline-block;
  padding: 0.1em 0.4em;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--bg-elevated);
  font-size: 0.85em;
  font-family: inherit;
}

main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem 4rem;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.25rem;
}

.search input {
  width: min(100%, 280px);
  padding: 0.7rem 1rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--bg-elevated);
  color: var(--ink);
  font: inherit;
  outline: none;
}

.search input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.filter-btn {
  padding: 0.45rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-size: 0.9rem;
  cursor: pointer;
}

.filter-btn[aria-selected='true'] {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--ink);
}

.meta {
  margin: 0 0 1.25rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
}

.card {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  padding: 1.25rem 1.35rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(160deg, rgba(26, 34, 44, 0.95), rgba(15, 20, 25, 0.8));
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s ease, transform 0.2s ease, background 0.2s ease;
}

.card:hover,
.card:focus-visible {
  border-color: var(--accent);
  transform: translateY(-2px);
  outline: none;
}

.card-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
}

.badge {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 0.25rem 0.55rem;
  border-radius: 999px;
}

.badge.technical {
  color: var(--technical);
  background: rgba(91, 159, 212, 0.15);
}

.badge.non-technical {
  color: var(--non-technical);
  background: rgba(212, 160, 91, 0.15);
}

.badge.uncategorized {
  color: var(--muted);
  background: rgba(139, 154, 171, 0.15);
}

.level {
  font-size: 0.8rem;
  color: var(--muted);
}

.card h2 {
  margin: 0;
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
  flex: 1;
}

.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
  font-size: 0.8rem;
  color: var(--muted);
}

.tag {
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  border: 1px solid var(--line);
}

.cta {
  margin-top: 0.25rem;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent);
}

.empty {
  text-align: center;
  color: var(--muted);
  padding: 3rem 1rem;
}

.hidden {
  display: none;
}

.site-footer {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem 3rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.site-footer a {
  color: var(--accent);
}

.site-footer code {
  font-size: 0.85em;
  padding: 0.1em 0.35em;
  border-radius: 4px;
  background: var(--bg-elevated);
}

@media (max-width: 600px) {
  .site-header {
    padding-top: 3rem;
  }

  .toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .search input {
    width: 100%;
  }
}