:root {
  --bg: #f7f7f9;
  --panel: #ffffff;
  --border: #e5e5ea;
  --text: #1c1c28;
  --text-muted: #6b6b76;
  --accent: #4f46e5;
  --accent-dark: #3730a3;
  --chip-bg: #eef2ff;
  --chip-text: #4338ca;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(20, 20, 40, 0.05), 0 2px 8px rgba(20, 20, 40, 0.06);
}

* { box-sizing: border-box; }

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

.wrap {
  max-width: 780px;
  margin: 0 auto;
  padding: 0 20px;
}

.site-header {
  background: linear-gradient(135deg, var(--accent), var(--accent-dark));
  color: #fff;
  padding: 40px 0 32px;
}
.site-header h1 { margin: 0; font-size: 2rem; letter-spacing: -0.02em; }
.site-header .tagline { margin: 6px 0 0; opacity: 0.9; font-size: 0.95rem; }

main.wrap { padding-top: 28px; padding-bottom: 60px; }

/* --- Search bar --- */

.search-bar { margin-bottom: 26px; }

#search-form {
  display: flex;
  gap: 8px;
}

input[type="search"] {
  flex: 1;
  min-width: 0;
  font: inherit;
  font-size: 1.05rem;
  padding: 13px 16px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--panel);
  box-shadow: var(--shadow);
}
input[type="search"]:focus { outline: 2px solid var(--accent); outline-offset: 1px; }

input[type="text"],
input[type="password"],
input[type="date"],
select {
  font: inherit;
  padding: 9px 11px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  color: var(--text);
}

button {
  font: inherit;
  padding: 12px 22px;
  border-radius: 999px;
  border: none;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  white-space: nowrap;
}
button:hover { background: var(--accent-dark); }

button.ghost {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--border);
}
button.ghost:hover { background: var(--chip-bg); border-color: var(--accent); }
button.ghost[aria-expanded="true"] { background: var(--chip-bg); border-color: var(--accent); color: var(--accent-dark); }

button.link-button {
  background: none;
  border: none;
  color: var(--accent-dark);
  padding: 6px 0;
  font-size: 0.88rem;
  text-decoration: underline;
  text-underline-offset: 2px;
}
button.link-button:hover { color: var(--accent); background: none; }

button:disabled { opacity: 0.4; cursor: not-allowed; }

/* --- Filters panel (collapsed by default) --- */

.filters-panel {
  margin-top: 12px;
  padding: 14px 16px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.filters-grid {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  align-items: center;
}
.filters-grid select { flex: 1 1 180px; }
#journal { flex: 1 1 160px; }

.date-label {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* --- Unlock panel --- */

#unlock-panel {
  margin-top: 14px;
  font-size: 0.88rem;
}
#unlock-panel summary {
  cursor: pointer;
  color: var(--text-muted);
  list-style: none;
}
#unlock-panel summary::-webkit-details-marker { display: none; }
#unlock-panel summary::before { content: "🔒 "; }
.unlock-row {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-top: 10px;
  flex-wrap: wrap;
}
#unlock-status { font-size: 0.85rem; color: var(--accent-dark); }

/* --- Results --- */

.results-summary {
  color: var(--text-muted);
  font-size: 0.88rem;
  margin-bottom: 10px;
  min-height: 1.2em;
}

.results-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.paper-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px 18px;
}
.paper-card h3 { margin: 0 0 6px; font-size: 1.05rem; line-height: 1.35; }
.paper-card .meta { margin: 0 0 8px; color: var(--text-muted); font-size: 0.86rem; }
.paper-card .tags { margin: 0 0 8px; font-size: 0; } /* collapse whitespace between chips */
.paper-card .citations { margin: 0 0 6px; font-size: 0.82rem; color: var(--text-muted); }
.paper-card a { color: var(--accent-dark); font-size: 0.88rem; }

.chip {
  display: inline-block;
  background: var(--chip-bg);
  color: var(--chip-text);
  border-radius: 999px;
  padding: 3px 10px;
  font-size: 0.76rem;
  margin: 0 6px 6px 0;
}

details.abstract { margin-top: 10px; border-top: 1px solid var(--border); padding-top: 8px; }
details.abstract summary {
  cursor: pointer;
  font-size: 0.85rem;
  color: var(--accent-dark);
}
details.abstract p { margin: 8px 0 0; font-size: 0.92rem; color: var(--text); }

.results-list li.empty {
  list-style: none;
  color: var(--text-muted);
  padding: 32px 20px;
  text-align: center;
  background: var(--panel);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}

#scroll-sentinel { height: 1px; }

.loading-message,
.end-message {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.86rem;
  padding: 16px 0;
  margin: 0;
}

.results-panel > .link-button {
  display: block;
  margin: 18px auto 0;
  text-align: center;
}

.site-footer {
  border-top: 1px solid var(--border);
  padding: 18px 0 40px;
  color: var(--text-muted);
  font-size: 0.82rem;
}
.site-footer a { color: var(--accent-dark); }

@media (max-width: 560px) {
  .wrap { padding: 0 14px; }
  #search-form { flex-wrap: wrap; }
  input[type="search"] { flex: 1 1 100%; }
  .site-header { padding: 28px 0 22px; }
}