:root {
  --bg: #f7f8fa;
  --card-bg: #ffffff;
  --border: #e2e5ea;
  --text: #1f2430;
  --text-muted: #6b7280;
  --accent: #2f5cff;
  --accent-soft: #eaf0ff;
  --tag-bg: #eef1f6;
  --china-color: #d9534f;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Segoe UI", "Microsoft YaHei", "PingFang SC", sans-serif;
  background: var(--bg);
  color: var(--text);
}

.topbar {
  padding: 20px 32px;
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
}
.topbar h1 { margin: 0 0 8px; font-size: 22px; }
.badge-preview {
  font-size: 12px;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 2px 8px;
  border-radius: 10px;
  font-weight: normal;
  vertical-align: middle;
}
.stats-bar {
  font-size: 13px;
  color: var(--text-muted);
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}
.stats-bar b { color: var(--text); }

.tabs {
  display: flex;
  gap: 4px;
  padding: 0 32px;
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
}
.tab-btn {
  border: none;
  background: none;
  padding: 12px 18px;
  font-size: 14px;
  cursor: pointer;
  color: var(--text-muted);
  border-bottom: 2px solid transparent;
}
.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
  font-weight: 600;
}

main { padding: 24px 32px 60px; max-width: 1100px; margin: 0 auto; }
.tab-panel { display: none; }
.tab-panel.active { display: block; }

.toolbar {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.toolbar input, .toolbar select {
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
}
.toolbar input { flex: 1; min-width: 200px; }

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px 20px;
  margin-bottom: 16px;
}

.subfield-card h2 { margin-top: 0; font-size: 18px; }
.subfield-card .scope-note { color: var(--text-muted); font-size: 13px; margin-bottom: 14px; }
.model-card {
  background: #fbfbfd;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 16px;
  margin-bottom: 10px;
}
.model-card h3 { margin: 0 0 6px; font-size: 15px; }
.model-card .core-idea { font-size: 13px; margin: 6px 0; }
.model-card .origin-papers, .model-card .evolution { font-size: 12px; color: var(--text-muted); }
.model-card .evolution ul, .model-card .origin-papers ul { margin: 4px 0; padding-left: 18px; }

.paper-row {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 16px;
  margin-bottom: 10px;
  cursor: pointer;
}
.paper-row:hover { border-color: var(--accent); }
.paper-title { font-size: 14px; font-weight: 600; margin-bottom: 4px; }
.paper-title-zh { font-size: 13px; color: var(--text-muted); margin-bottom: 4px; }
.paper-meta { font-size: 12px; color: var(--text-muted); }
.paper-tags { margin-top: 6px; display: flex; gap: 6px; flex-wrap: wrap; }
.tag {
  font-size: 11px;
  background: var(--tag-bg);
  color: var(--text-muted);
  padding: 2px 8px;
  border-radius: 10px;
}
.tag.china { background: #fdecea; color: var(--china-color); }
.paper-abstract {
  display: none;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px dashed var(--border);
  font-size: 13px;
  line-height: 1.6;
}
.paper-abstract.show { display: block; }
.paper-abstract .en { color: var(--text-muted); margin-bottom: 8px; }
.no-abstract { color: var(--text-muted); font-style: italic; }

.cluster-card { margin-bottom: 18px; }
.cluster-card h2 { margin: 0 0 4px; font-size: 17px; }
.cluster-card .count { font-size: 12px; color: var(--text-muted); margin-bottom: 10px; }
.cluster-card .summary { font-size: 13px; line-height: 1.7; margin-bottom: 12px; }
.cluster-papers { font-size: 12px; }
.cluster-papers summary { cursor: pointer; color: var(--accent); }
.cluster-papers ul { margin: 8px 0 0; padding-left: 18px; }

.empty-state { color: var(--text-muted); padding: 40px 0; text-align: center; }
.result-count { font-size: 12px; color: var(--text-muted); margin-bottom: 10px; }