:root {
  --bg: #ffffff;
  --fg: #1a1a1a;
  --muted: #666666;
  --border: #e2e2e2;
  --accent: #2952a3;
  --accent-bg: #eef2fb;
  --chip-bg: #f4f4f4;
  --chip-active-bg: #2952a3;
  --chip-active-fg: #ffffff;
  --radius: 6px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--fg);
  background: var(--bg);
  line-height: 1.5;
}

.site-header {
  border-bottom: 1px solid var(--border);
  padding: 2rem 1rem 1.5rem;
}

.header-inner, .container {
  max-width: 860px;
  margin: 0 auto;
}

.site-header h1 {
  margin: 0 0 0.4rem;
  font-size: 1.6rem;
}

.subtitle {
  color: var(--muted);
  margin: 0 0 0.6rem;
}

.links a { color: var(--accent); text-decoration: none; }
.links a:hover { text-decoration: underline; }

.container { padding: 1.5rem 1rem 3rem; }

#search-box {
  width: 100%;
  font-size: 1rem;
  padding: 0.65rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  outline: none;
}

#search-box:focus {
  border-color: var(--accent);
}

.controls-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-top: 0.75rem;
  flex-wrap: wrap;
}

.semantic-toggle {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9rem;
  color: var(--muted);
  cursor: pointer;
}

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

#sort-select {
  font-size: 0.9rem;
  padding: 0.3rem 0.5rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: white;
}

.clear-btn {
  font-size: 0.85rem;
  color: var(--accent);
  background: none;
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  padding: 0.3rem 0.6rem;
  cursor: pointer;
}

.category-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.9rem;
}

.chip {
  font-size: 0.8rem;
  padding: 0.3rem 0.65rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--chip-bg);
  color: var(--fg);
  cursor: pointer;
  user-select: none;
}

.chip.active {
  background: var(--chip-active-bg);
  color: var(--chip-active-fg);
  border-color: var(--chip-active-bg);
}

.result-count {
  color: var(--muted);
  font-size: 0.85rem;
  margin: 1.2rem 0 0.4rem;
}

.paper-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.paper-item {
  padding: 0.9rem 0;
  border-bottom: 1px solid var(--border);
}

.paper-title a {
  color: var(--fg);
  text-decoration: none;
  font-weight: 600;
  font-size: 1rem;
}

.paper-title a:hover {
  color: var(--accent);
  text-decoration: underline;
}

.paper-meta {
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 0.25rem;
}

.paper-categories {
  margin-top: 0.4rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem;
}

.tag {
  font-size: 0.72rem;
  background: var(--accent-bg);
  color: var(--accent);
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
}

.empty-state {
  color: var(--muted);
  text-align: center;
  padding: 2rem 0;
}

.site-footer {
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
  text-align: center;
  padding: 1.5rem 1rem;
}

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