:root {
      --bg: #020617;
      --bg-soft: #020617;
      --card: rgba(15, 23, 42, 0.95);
      --card-soft: rgba(15, 23, 42, 0.9);
      --accent: #38bdf8;
      --accent-soft: rgba(56, 189, 248, 0.2);
      --border-subtle: rgba(148, 163, 184, 0.3);
      --text-main: #e5e7eb;
      --text-muted: #9ca3af;
      --text-soft: #6b7280;
      --error: #f97373;
      --shadow-soft: 0 24px 80px rgba(15, 23, 42, 0.75);
      --radius-lg: 1.5rem;
      --radius-md: 0.9rem;
      --radius-sm: 0.6rem;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      min-height: 100vh;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text",
        "Segoe UI", sans-serif;
      background:
        radial-gradient(circle at top left, #0f172a, #020617 55%),
        radial-gradient(circle at bottom right, #0b1120, #020617 65%);
      color: var(--text-main);
      display: flex;
      justify-content: center;
      padding: 2rem 1rem 3rem;
    }

    .page {
      width: 100%;
      max-width: 1120px;
      margin: auto;
    }

    .header {
      display: flex;
      flex-direction: column;
      gap: 0.4rem;
      margin-bottom: 1.75rem;
    }

    .badge {
      display: inline-flex;
      align-items: center;
      gap: 0.4rem;
      font-size: 0.75rem;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      padding: 0.25rem 0.75rem;
      border-radius: 999px;
      border: 1px solid var(--border-subtle);
      background: rgba(15, 23, 42, 0.6);
      color: var(--text-soft);
      backdrop-filter: blur(10px);
      width: fit-content;
    }

    .badge-dot {
      width: 7px;
      height: 7px;
      border-radius: 999px;
      background: var(--accent);
      box-shadow: 0 0 0 4px var(--accent-soft);
    }

    h1 {
      font-size: clamp(1.8rem, 3vw, 2.3rem);
      margin: 0;
      letter-spacing: -0.03em;
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: 0.4rem;
    }

    h1 span.highlight {
      color: var(--accent);
    }

    .subtitle {
      margin: 0.25rem 0 0;
      color: var(--text-muted);
      font-size: 0.9rem;
      max-width: 34rem;
      line-height: 1.4;
    }

    .grid {
      display: grid;
      grid-template-columns: minmax(0, 3fr) minmax(0, 2.4fr);
      gap: 1.5rem;
    }

    @media (max-width: 880px) {
      .grid {
        grid-template-columns: minmax(0, 1fr);
      }
    }

    .card {
      background: var(--card);
      border-radius: var(--radius-lg);
      box-shadow: var(--shadow-soft);
      border: 1px solid rgba(148, 163, 184, 0.22);
      padding: 1.4rem 1.5rem 1.6rem;
      position: relative;
      overflow: hidden;
    }

    .card::before {
      content: "";
      position: absolute;
      inset: 0;
      background: radial-gradient(circle at top right,
        rgba(56, 189, 248, 0.12),
        transparent 55%);
      opacity: 0.9;
      pointer-events: none;
    }

    .card-inner {
      position: relative;
      z-index: 1;
    }

    .card-header {
      display: flex;
      justify-content: space-between;
      gap: 0.75rem;
      align-items: center;
      margin-bottom: 1rem;
    }

    .card-title {
      font-size: 1rem;
      font-weight: 600;
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }

    .card-title-pill {
      font-size: 0.7rem;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      padding: 0.15rem 0.6rem;
      border-radius: 999px;
      border: 1px solid var(--border-subtle);
      color: var(--text-soft);
    }

    .card-description {
      font-size: 0.8rem;
      color: var(--text-soft);
      margin-bottom: 0.7rem;
    }

    label {
      display: block;
      font-size: 0.78rem;
      font-weight: 500;
      color: var(--text-soft);
      margin-bottom: 0.25rem;
    }

    .input-row {
      display: flex;
      gap: 0.75rem;
      flex-wrap: wrap;
      margin-bottom: 0.75rem;
    }

    .field {
      flex: 1 1 140px;
      min-width: 0;
    }

    .field-full {
      width: 100%;
      margin-bottom: 0.75rem;
    }

    .input, select, textarea {
      width: 100%;
      border-radius: var(--radius-sm);
      border: 1px solid rgba(51, 65, 85, 0.9);
      background: rgba(15, 23, 42, 0.9);
      color: var(--text-main);
      font-size: 0.85rem;
      padding: 0.6rem 0.75rem;
      outline: none;
      transition: border-color 0.16s ease, box-shadow 0.16s ease,
        background 0.16s ease, transform 0.06s ease;
    }

    .input::placeholder,
    textarea::placeholder {
      color: var(--text-soft);
    }

    .input:focus,
    select:focus,
    textarea:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 1px rgba(56, 189, 248, 0.3);
      background: rgba(15, 23, 42, 0.98);
      transform: translateY(-0.5px);
    }

    textarea {
      resize: vertical;
      min-height: 80px;
      max-height: 220px;
      line-height: 1.4;
    }

    .hint {
      margin-top: 0.2rem;
      font-size: 0.72rem;
      color: var(--text-soft);
    }

    .btn-row {
      display: flex;
      gap: 0.5rem;
      margin-top: 0.4rem;
      align-items: center;
      flex-wrap: wrap;
    }

    .btn {
      border-radius: 999px;
      border: none;
      padding: 0.55rem 1.1rem;
      font-size: 0.8rem;
      font-weight: 500;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 0.4rem;
      background: linear-gradient(135deg, #38bdf8, #22c55e);
      color: #020617;
      box-shadow: 0 16px 35px rgba(56, 189, 248, 0.28);
      transition: transform 0.12s ease, box-shadow 0.12s ease,
        filter 0.12s ease;
      white-space: nowrap;
    }

    .btn.secondary {
      background: rgba(15, 23, 42, 0.9);
      color: var(--text-main);
      border: 1px solid var(--border-subtle);
      box-shadow: none;
    }

    .btn:disabled {
      opacity: 0.65;
      cursor: default;
      box-shadow: none;
      transform: none;
    }

    .btn:not(:disabled):hover {
      transform: translateY(-1px);
      filter: brightness(1.05);
      box-shadow: 0 22px 40px rgba(56, 189, 248, 0.38);
    }

    .btn-icon {
      font-size: 1rem;
    }

    .pill {
      border-radius: 999px;
      border: 1px dashed rgba(148, 163, 184, 0.5);
      padding: 0.25rem 0.6rem;
      font-size: 0.72rem;
      color: var(--text-soft);
    }

    .citation-output {
      margin-top: 0.8rem;
      background: var(--bg-soft);
      border-radius: var(--radius-md);
      border: 1px solid rgba(148, 163, 184, 0.4);
      padding: 0.85rem 1.1rem;
      font-family: "Georgia", "Times New Roman", serif;
      font-size: 0.85rem;
      line-height: 1.5;
      max-height: 200px;
      overflow-y: auto;
    }

    .citation-output.empty {
      border-style: dashed;
      color: var(--text-soft);
      font-style: italic;
    }

    .citation-line {
      display: block;
      padding-left: 2em;
      text-indent: -2em;
      word-wrap: break-word;
      overflow-wrap: break-word;
    }

    .citation-label {
      font-size: 0.78rem;
      color: var(--text-soft);
      margin-bottom: 0.2rem;
    }

    .error {
      font-size: 0.75rem;
      color: var(--error);
      margin-top: 0.25rem;
    }

    /* Semantic Scholar section */
    .results {
      margin-top: 0.7rem;
      display: flex;
      flex-direction: column;
      gap: 0.5rem;
      max-height: 250px;
      overflow-y: auto;
    }

    .paper {
      border-radius: var(--radius-md);
      background: rgba(15, 23, 42, 0.9);
      border: 1px solid rgba(148, 163, 184, 0.35);
      padding: 0.6rem 0.75rem;
    }

    .paper-header {
      display: flex;
      justify-content: space-between;
      gap: 0.5rem;
      align-items: flex-start;
    }

    .paper-title {
      font-size: 0.86rem;
      font-weight: 500;
      margin-bottom: 0.15rem;
    }

    .paper-meta {
      font-size: 0.74rem;
      color: var(--text-soft);
    }

    .paper-actions {
      display: flex;
      flex-direction: column;
      gap: 0.25rem;
      align-items: flex-end;
    }

    .paper-link {
      font-size: 0.74rem;
      color: var(--accent);
      text-decoration: none;
      opacity: 0.85;
    }

    .paper-link:hover {
      opacity: 1;
      text-decoration: underline;
    }

    .guide-card {
      margin-top: 1.5rem;
      background: var(--card-soft);
      border-radius: var(--radius-lg);
      border: 1px solid rgba(148, 163, 184, 0.23);
      padding: 1.3rem 1.5rem 1.4rem;
    }

    .guide-title {
      font-size: 0.98rem;
      font-weight: 600;
      margin: 0 0 0.35rem;
      display: flex;
      align-items: center;
      gap: 0.4rem;
    }

    .guide-title span {
      font-size: 0.8rem;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      color: var(--text-soft);
    }

    .guide-section-title {
      font-size: 0.86rem;
      font-weight: 600;
      margin: 0.8rem 0 0.25rem;
    }

    .guide-text {
      font-size: 0.78rem;
      color: var(--text-muted);
      line-height: 1.5;
      margin: 0.15rem 0;
    }

    .guide-list {
      font-size: 0.78rem;
      color: var(--text-muted);
      margin: 0.1rem 0 0.15rem 0.9rem;
      padding-left: 0.4rem;
    }

    .guide-list li {
      margin: 0.08rem 0;
    }

    .guide-note {
      font-size: 0.72rem;
      color: var(--text-soft);
      margin-top: 0.5rem;
      font-style: italic;
    }

    code {
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas,
        "Liberation Mono", "Courier New", monospace;
      font-size: 0.75rem;
      padding: 0.05rem 0.25rem;
      border-radius: 0.4rem;
      background: rgba(15, 23, 42, 0.9);
      border: 1px solid rgba(148, 163, 184, 0.4);
      color: var(--accent);
    }

    .footer {
      margin-top: 1.75rem;
      font-size: 0.7rem;
      color: var(--text-soft);
      display: flex;
      justify-content: space-between;
      gap: 0.75rem;
      flex-wrap: wrap;
    }

    .footer a {
      color: var(--accent);
      text-decoration: none;
    }

    .footer a:hover {
      text-decoration: underline;
    }

/* ============================================================
   THEME VARIABLES (DARK / LIGHT)
   ============================================================ */

:root {
  --color-bg: #020617;
  --color-bg-elevated: #020617;
  --color-border: #1f2937;
  --color-text: #e5e7eb;
  --color-text-soft: #9ca3af;
  --color-accent: #6366f1;
  --color-accent-soft: rgba(99, 102, 241, 0.16);
  --color-input-bg: #020617;
  --color-input-border: #1f2937;
  --color-badge-bg: rgba(15, 23, 42, 0.9);
  --shadow-soft: 0 20px 40px rgba(15, 23, 42, 0.7);
}

:root[data-theme="light"] {
  --color-bg: #f4f4f5;
  --color-bg-elevated: #ffffff;
  --color-border: #e4e4e7;
  --color-text: #020617;
  --color-text-soft: #6b7280;
  --color-accent: #4f46e5;
  --color-accent-soft: rgba(79, 70, 229, 0.12);
  --color-input-bg: #ffffff;
  --color-input-border: #d4d4d8;
  --color-badge-bg: rgba(255, 255, 255, 0.8);
  --shadow-soft: 0 18px 30px rgba(15, 23, 42, 0.16);
}

/* Apply theme colors */

body {
  background: radial-gradient(circle at top, rgba(56,189,248,0.18), transparent 55%),
              radial-gradient(circle at bottom, rgba(79,70,229,0.21), transparent 60%),
              var(--color-bg);
  color: var(--color-text);
}

.page {
  color: var(--color-text);
}

.card {
  background: var(--color-bg-elevated);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-soft);
}

.header .subtitle,
.card-description,
.hint,
.guide-text {
  color: var(--color-text-soft);
}

.badge {
  background: var(--color-badge-bg);
  border-color: rgba(148, 163, 184, 0.5);
  color: var(--color-text-soft);
}

.input {
  background: var(--color-input-bg);
  border-color: var(--color-input-border);
  color: var(--color-text);
}

.input::placeholder {
  color: var(--color-text-soft);
}

.btn {
  background: var(--color-accent);
  border-color: transparent;
  color: #f9fafb;
}

.btn.secondary {
  background: transparent;
  border-color: rgba(148, 163, 184, 0.7);
  color: var(--color-text-soft);
}

.citation-output {
  background: rgba(15, 23, 42, 0.5);
  border-color: rgba(148, 163, 184, 0.5);
}

:root[data-theme="light"] .citation-output {
  background: #f9fafb;
}

/* ============================================================
   HEADER TOP ROW & THEME TOGGLE
   ============================================================ */

.header-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

/* Toggle container */

.theme-toggle {
  border: none;
  background: transparent;
  padding: 0;
  cursor: pointer;
  outline: none;
}

.theme-toggle-track {
  position: relative;
  width: 54px;
  height: 28px;
  border-radius: 999px;
  background: rgba(15, 23, 42, 0.7);
  border: 1px solid rgba(148, 163, 184, 0.7);
  display: flex;
  align-items: center;
  padding: 0 5px;
  box-sizing: border-box;
  overflow: hidden;
  transition: background 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
}

:root[data-theme="light"] .theme-toggle-track {
  background: #e5e7eb;
  border-color: #d4d4d8;
}

/* Toggle thumb */

.theme-toggle-thumb {
  position: absolute;
  width: 22px;
  height: 22px;
  border-radius: 999px;
  background: #f9fafb;
  box-shadow: 0 6px 16px rgba(15, 23, 42, 0.35);
  transform: translateX(0);
  transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Icons */

.theme-toggle-icon {
  position: relative;
  font-size: 14px;
  flex: 0 0 auto;
  opacity: 0.7;
  transition: opacity 0.25s ease, transform 0.25s ease;
}

.theme-toggle-icon--moon {
  margin-right: auto;
  transform: translateX(0);
}

.theme-toggle-icon--sun {
  margin-left: auto;
  transform: translateX(6px);
  opacity: 0;
}

/* State: light theme */

:root[data-theme="light"] .theme-toggle-thumb {
  transform: translateX(24px);
}

:root[data-theme="light"] .theme-toggle-icon--moon {
  opacity: 0;
  transform: translateX(-6px) scale(0.9);
}

:root[data-theme="light"] .theme-toggle-icon--sun {
  opacity: 1;
  transform: translateX(0) scale(1.03);
}

/* Hover / focus */

.theme-toggle-track:hover {
  box-shadow: 0 0 0 1px rgba(129, 140, 248, 0.35);
}

.theme-toggle:focus-visible .theme-toggle-track {
  box-shadow: 0 0 0 2px rgba(129, 140, 248, 0.55);
}

/* ============================================================
   LIGHT THEME FIXES: INPUT FOCUS + RESULTS LIST
   ============================================================ */

/* Ensure focused inputs look light when in light theme */
.input:focus {
  background: var(--color-input-bg);
  border-color: var(--color-accent);
  outline: none;
  box-shadow: 0 0 0 1px rgba(129, 140, 248, 0.5);
}

/* Results container for Semantic Scholar + Crossref */
.results {
  border-radius: 1rem;
  border: 1px solid var(--color-border);
  background: rgba(15, 23, 42, 0.7);
  padding: 0.75rem;
  margin-top: 1rem;
  max-height: 280px;
  overflow: auto;
}

:root[data-theme="light"] .results {
  background: #ffffff;
  border-color: #e4e4e7;
}

/* Individual paper entries */
.paper {
  background: rgba(15, 23, 42, 0.8);
  border-radius: 0.75rem;
  padding: 0.75rem 0.85rem;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  margin-bottom: 0.5rem;
  transition:
    background 0.25s ease,
    transform 0.15s ease,
    box-shadow 0.2s ease;
}

.paper:last-child {
  margin-bottom: 0;
}

.paper:hover {
  transform: translateY(-1px);
  box-shadow: 0 10px 25px rgba(15, 23, 42, 0.7);
}

:root[data-theme="light"] .paper {
  background: #f9fafb;
  box-shadow: 0 8px 18px rgba(15, 23, 42, 0.08);
}

:root[data-theme="light"] .paper:hover {
  box-shadow: 0 12px 30px rgba(15, 23, 42, 0.12);
}

/* Paper text colors in light theme */
:root[data-theme="light"] .paper-title {
  color: #111827;
}

:root[data-theme="light"] .paper-meta {
  color: #6b7280;
}

/* Make citation output background match theme (already partially done, reinforcing) */
:root[data-theme="light"] .citation-output {
  background: #f9fafb;
  border-color: #e4e4e7;
}

/* ============================================================
   INDEX HERO ROW + AVATAR
   ============================================================ */

.hero-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  margin-top: 1rem;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.hero-text {
  flex: 1 1 260px;
  min-width: 0;
}

.hero-avatar-link {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
}

.hero-avatar {
  width: 112px;
  height: 112px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid rgba(148, 163, 184, 0.7);
  box-shadow: 0 16px 32px rgba(15, 23, 42, 0.7);
  transition:
    transform 0.18s ease,
    box-shadow 0.2s ease,
    border-color 0.2s ease;
}

.hero-avatar-link:hover .hero-avatar {
  transform: translateY(-2px) scale(1.02);
  box-shadow: 0 20px 40px rgba(15, 23, 42, 0.85);
  border-color: rgba(129, 140, 248, 0.9);
}

:root[data-theme="light"] .hero-avatar {
  box-shadow: 0 14px 28px rgba(15, 23, 42, 0.16);
}

:root[data-theme="light"] .hero-avatar-link:hover .hero-avatar {
  box-shadow: 0 18px 36px rgba(15, 23, 42, 0.2);
}

@media (max-width: 720px) {
  .hero-row {
    flex-direction: row;
    align-items: flex-start;
  }

  .hero-avatar {
    width: 96px;
    height: 96px;
  }
}