:root {
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #dbeafe;
  --primary-dark: #1e40af;
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-hover: #f1f5f9;
  --text: #1e293b;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.08);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.2s ease;
  --footer-bg: #1e293b;
  --footer-text: #94a3b8;
  --success: #10b981;
  --danger: #ef4444;
}

html.dark {
  --primary: #60a5fa;
  --primary-hover: #93bbfd;
  --primary-light: #1e3a5f;
  --primary-dark: #93bbfd;
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-hover: #334155;
  --text: #f1f5f9;
  --text-secondary: #94a3b8;
  --border: #334155;
  --shadow: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.4);
  --footer-bg: #020617;
  --footer-text: #64748b;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background var(--transition), color var(--transition);
}

.container { max-width: 1120px; margin: 0 auto; padding: 0 24px; }

/* ── Navbar ── */
.navbar {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  background: rgba(255,255,255,0.85);
  transition: background var(--transition), border-color var(--transition);
}
html.dark .navbar { background: rgba(15,23,42,0.85); }
.nav-container {
  max-width: 1120px; margin: 0 auto; padding: 0 24px;
  display: flex; align-items: center; height: 64px; gap: 8px;
}
.nav-brand {
  font-size: 1.35rem; font-weight: 800;
  color: var(--primary); text-decoration: none;
  letter-spacing: -0.5px;
}
.nav-brand span { color: var(--text); }
.nav-tagline {
  color: var(--text-secondary); font-size: 0.85rem;
  margin-left: 4px; padding-left: 12px;
  border-left: 1px solid var(--border);
}
.nav-spacer { flex: 1; }

/* Dark mode toggle */
.dark-toggle {
  position: relative; width: 48px; height: 26px;
  background: var(--border); border-radius: 13px;
  cursor: pointer; transition: background var(--transition);
  flex-shrink: 0;
}
.dark-toggle input { opacity: 0; width: 0; height: 0; position: absolute; }
.dark-toggle .slider {
  position: absolute; top: 3px; left: 3px;
  width: 20px; height: 20px; border-radius: 50%;
  background: var(--surface); transition: transform var(--transition);
  box-shadow: var(--shadow);
  display: flex; align-items: center; justify-content: center;
  font-size: 12px;
}
.dark-toggle .slider .icon { transition: opacity var(--transition); }
.dark-toggle .slider .sun { display: none; }
.dark-toggle .slider .moon { display: inline; }
html.dark .dark-toggle { background: var(--primary); }
html.dark .dark-toggle .slider { transform: translateX(22px); }
html.dark .dark-toggle .slider .sun { display: inline; }
html.dark .dark-toggle .slider .moon { display: none; }

/* ── Hero ── */
.hero {
  text-align: center; padding: 64px 24px 48px;
  background: linear-gradient(135deg, var(--primary-light) 0%, transparent 60%);
  border-radius: 0 0 var(--radius) var(--radius);
  margin-bottom: 8px; transition: background var(--transition);
}
.hero h1 {
  font-size: 2.75rem; font-weight: 800; color: var(--text);
  letter-spacing: -1px; margin-bottom: 8px;
}
.hero h1 span { color: var(--primary); }
.hero p { font-size: 1.1rem; color: var(--text-secondary); max-width: 480px; margin: 0 auto; }

/* ── Tool Grid (index) ── */
.tool-grid { display: flex; flex-direction: column; gap: 36px; padding-bottom: 64px; }
.category h2 {
  font-size: 1.15rem; font-weight: 700; color: var(--text);
  margin-bottom: 14px; padding-bottom: 8px;
  border-bottom: 2px solid var(--border);
  display: flex; align-items: center; gap: 8px;
}
.category h2 .count {
  font-size: 0.75rem; font-weight: 600; color: var(--text-secondary);
  background: var(--surface-hover); padding: 2px 10px;
  border-radius: 20px; margin-left: auto;
}
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
  gap: 12px;
}
.card {
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 18px 14px 14px;
  text-decoration: none; color: var(--text);
  transition: all var(--transition); position: relative; overflow: hidden;
  text-align: center;
}
.card::before {
  content: ''; position: absolute; inset: 0;
  background: linear-gradient(135deg, var(--primary) 0%, transparent 60%);
  opacity: 0; transition: opacity var(--transition);
}
.card:hover {
  border-color: var(--primary); transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}
.card:hover::before { opacity: 0.04; }
.card .card-icon { font-size: 1.6rem; line-height: 1; margin-bottom: 4px; position: relative; }
.card .card-title { font-weight: 600; font-size: 0.9rem; position: relative; }
.card .card-desc { font-size: 0.75rem; color: var(--text-secondary); line-height: 1.3; position: relative; }

/* ── Tool Page ── */
.tool-page-wrapper {
  display: flex; justify-content: center; align-items: flex-start;
  min-height: calc(100vh - 64px - 72px); padding: 32px 0;
}
.tool-container {
  width: 100%; max-width: 620px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 40px 40px;
  box-shadow: var(--shadow);
  transition: background var(--transition), border-color var(--transition), box-shadow var(--transition);
}
.tool-header {
  text-align: center; margin-bottom: 28px; position: relative;
}
.tool-back {
  display: inline-flex; align-items: center; justify-content: center;
  width: 32px; height: 32px; border-radius: 8px;
  color: var(--text-secondary); text-decoration: none;
  font-size: 1.1rem; transition: all var(--transition);
  position: absolute; left: 0; top: 0;
}
.tool-back:hover { background: var(--surface-hover); color: var(--text); }
.tool-header-icon { font-size: 2.2rem; display: block; margin-bottom: 6px; }
.tool-header h1 { font-size: 1.4rem; font-weight: 700; color: var(--text); margin-bottom: 4px; }
.tool-header .tool-desc { color: var(--text-secondary); font-size: 0.9rem; margin: 0; }

/* Upload Zone — state overrides for Tailwind */
.upload-zone { cursor: pointer; position: relative; transition: all 0.2s ease; }
.upload-zone input[type="file"] { display: none; }
.upload-zone:hover { border-color: #3b82f6 !important; background-color: #eff6ff !important; }
html.dark .upload-zone:hover { border-color: #60a5fa !important; background-color: rgba(30,58,95,0.4) !important; }
.upload-zone.dragover { border-color: #3b82f6 !important; background-color: #eff6ff !important; transform: scale(1.01); }
html.dark .upload-zone.dragover { border-color: #60a5fa !important; background-color: rgba(30,58,95,0.4) !important; }
.upload-zone.has-file { padding: 0 !important; border-style: solid !important; border-color: #d1d5db !important; background: #fff !important; cursor: default; }
html.dark .upload-zone.has-file { border-color: #4b5563 !important; background: #1f2937 !important; }
.upload-zone.has-file:hover { background: #fff !important; }
html.dark .upload-zone.has-file:hover { background: #1f2937 !important; }
.upload-placeholder { pointer-events: none; }

/* Merge file cards */
.merge-card {
  display: flex; align-items: center; gap: 12px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 10px 14px;
  animation: fadeIn 0.25s ease;
  transition: all var(--transition);
}
.merge-card:hover { border-color: var(--primary); box-shadow: var(--shadow); }
.merge-card-order {
  width: 24px; height: 24px; border-radius: 50%;
  background: var(--primary); color: #fff;
  display: flex; align-items: center; justify-content: center;
  font-size: 0.75rem; font-weight: 700; flex-shrink: 0;
}
.merge-card-thumb { flex-shrink: 0; }
.merge-thumb {
  width: 72px; height: 96px; object-fit: cover;
  border-radius: 6px; border: 1px solid var(--border);
  background: #fff;
}
html.dark .merge-thumb { border-color: #4b5563; }
.merge-thumb-placeholder {
  display: flex; align-items: center; justify-content: center;
  background: var(--surface-hover);
}
.merge-card-info { flex: 1; min-width: 0; }
.merge-card-name {
  display: block; font-weight: 600; font-size: 0.85rem;
  color: var(--text); overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.merge-card-size {
  display: block; font-size: 0.75rem; color: var(--text-secondary); margin-top: 2px;
}
.merge-card-actions {
  display: flex; gap: 4px; flex-shrink: 0;
}
.merge-card-actions button {
  width: 28px; height: 28px; border: 1px solid var(--border);
  border-radius: 6px; background: var(--surface);
  color: var(--text-secondary); cursor: pointer;
  font-size: 0.75rem; display: flex; align-items: center; justify-content: center;
  transition: all var(--transition);
}
.merge-card-actions button:hover:not(:disabled) {
  background: var(--primary); color: #fff; border-color: var(--primary);
}
.merge-card-actions button:disabled { opacity: 0.35; cursor: not-allowed; }
.merge-btn-remove:hover:not(:disabled) { background: var(--danger) !important; border-color: var(--danger) !important; }
.merge-card-dragging { opacity: 0.4; }
.merge-card-over { border-color: var(--primary) !important; box-shadow: 0 0 0 2px var(--primary-light); }

/* ── Reorder Viewer ── */
.reorder-layout {
  display: flex; flex-direction: column; gap: 12px; margin-top: 16px;
}
.reorder-thumb-panel {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  overflow: hidden;
}
.reorder-thumb-header {
  padding: 10px 14px; font-weight: 700; font-size: 0.85rem;
  border-bottom: 1px solid var(--border);
  background: var(--surface-hover);
  color: var(--text);
}
.reorder-thumb-list {
  padding: 10px; overflow-x: auto; overflow-y: hidden;
  display: flex; flex-direction: row; gap: 12px;
  min-height: 160px;
}
.reorder-thumb-item {
  flex-shrink: 0; width: 170px;
  border: 2px solid transparent;
  border-radius: 8px; padding: 8px 6px 6px;
  cursor: pointer; transition: all var(--transition);
  background: var(--surface-hover);
  display: flex; flex-direction: column; align-items: center;
}
.reorder-thumb-item:hover { border-color: var(--primary); }
.reorder-thumb-item.active { border-color: var(--primary); background: var(--primary-light); }
.reorder-thumb-item img {
  width: 156px; height: auto; display: block;
  border-radius: 4px;
}
.reorder-thumb-label {
  font-size: 0.75rem; font-weight: 600;
  color: var(--text-secondary); margin-top: 4px;
  white-space: nowrap;
}
.reorder-thumb-label .old-num { color: var(--text); }
.reorder-thumb-label .arrow { color: var(--primary); margin: 0 2px; }
.reorder-thumb-label .new-num { color: var(--success); }
.reorder-thumb-dragging { opacity: 0.4; }
.reorder-thumb-over { border-color: var(--primary) !important; box-shadow: 0 0 0 2px var(--primary-light); }

/* Delete pages overlay */
.reorder-thumb-item.delete-active { border-color: var(--danger) !important; background: #fef2f2 !important; }
html.dark .reorder-thumb-item.delete-active { background: #3b1a1a !important; }
.delete-thumb-wrap { position: relative; display: inline-block; }
.delete-overlay {
  position: absolute; inset: 0;
  background: rgba(239,68,68,0.35);
  display: flex; align-items: center; justify-content: center;
  border-radius: 4px;
}
.delete-overlay-icon {
  color: #fff; font-size: 1.5rem; font-weight: 700;
  text-shadow: 0 1px 4px rgba(0,0,0,0.5);
}

.reorder-actions { margin-top: 4px; }

@media (max-width: 768px) {
  .reorder-thumb-item { width: 130px; }
  .reorder-thumb-item img { width: 118px; }
}

/* Tailwind overrides for dark mode */
html.dark .tool-form input, html.dark .tool-form select { background: #1e293b; border-color: #334155; color: #f1f5f9; }
html.dark .tool-form input:focus, html.dark .tool-form select:focus { border-color: #60a5fa; --tw-ring-color: rgba(96,165,250,0.2); }
/* File info card */
.file-info-card {
  display: flex; align-items: center; gap: 12px;
  padding: 14px 16px;
  animation: fadeIn 0.25s ease;
}
.file-icon { font-size: 1.5rem; flex-shrink: 0; }
.file-details { flex: 1; min-width: 0; text-align: left; }
.file-name { display: block; font-weight: 600; font-size: 0.9rem; color: var(--text); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.file-size { display: block; font-size: 0.8rem; color: var(--text-secondary); margin-top: 2px; }
.file-remove {
  background: none; border: none; font-size: 1.3rem;
  color: var(--text-secondary); cursor: pointer;
  padding: 4px 8px; border-radius: 6px; line-height: 1;
  transition: all var(--transition); flex-shrink: 0;
}
.file-remove:hover { background: var(--danger); color: #fff; }

/* Multiple file list */
.file-list { margin: 16px 0 20px; }
.file-list-item {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 12px; border-radius: var(--radius-sm);
  background: var(--surface-hover); margin-bottom: 6px;
  animation: fadeIn 0.2s ease;
}
.file-list-item .file-icon { font-size: 1.2rem; }
.file-list-item .file-details { flex: 1; min-width: 0; }
.file-list-item .file-name { font-size: 0.85rem; }
.file-list-item .file-size { font-size: 0.75rem; }
.file-list-item .file-remove { font-size: 1rem; }

/* Form fields */
.tool-form .form-group { margin-bottom: 18px; }
.tool-form label {
  display: block; font-weight: 600; margin-bottom: 6px;
  font-size: 0.85rem; color: var(--text-secondary); text-transform: uppercase;
  letter-spacing: 0.4px;
}
.tool-form input, .tool-form select {
  width: 100%; padding: 11px 14px;
  background: var(--bg); border: 1px solid var(--border);
  border-radius: var(--radius-sm); font-size: 0.95rem;
  color: var(--text); transition: all var(--transition);
  font-family: inherit;
}
.tool-form input::placeholder { color: var(--text-secondary); opacity: 0.6; }
.tool-form input:focus, .tool-form select:focus {
  outline: none; border-color: var(--primary);
  box-shadow: 0 0 0 4px var(--primary-light);
}
.form-row { display: flex; gap: 14px; }
.form-row .form-group { flex: 1; }

/* Submit button */
.btn-submit {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff; border: none; padding: 14px 30px;
  border-radius: var(--radius-sm); font-size: 1rem; font-weight: 600;
  cursor: pointer; transition: all var(--transition); width: 100%;
  font-family: inherit; letter-spacing: 0.2px;
  position: relative; overflow: hidden;
  margin-top: 4px;
}
.btn-submit::after {
  content: ''; position: absolute; inset: 0;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
  transform: translateX(-100%);
  transition: transform 0.5s;
}
.btn-submit:hover::after { transform: translateX(100%); }
.btn-submit:hover { transform: translateY(-1px); box-shadow: 0 4px 14px rgba(37,99,235,0.35); }
.btn-submit:active { transform: translateY(0); }
.btn-submit:disabled { opacity: 0.65; cursor: not-allowed; transform: none; }
.btn-submit:disabled::after { display: none; }
.btn-submit .btn-icon { font-size: 1.1rem; }

/* Flash */
.flash-message {
  background: var(--primary-light); color: var(--primary-dark);
  border: 1px solid var(--primary);
  padding: 14px 18px; margin: 20px 0; border-radius: var(--radius-sm);
  font-size: 0.9rem; font-weight: 500;
  animation: slideDown 0.3s ease;
}
@keyframes slideDown { from { opacity: 0; transform: translateY(-10px); } to { opacity: 1; transform: translateY(0); } }

/* Footer */
footer {
  background: var(--footer-bg); color: var(--footer-text);
  text-align: center; padding: 24px 0; margin-top: 48px;
  font-size: 0.85rem;
}

/* Loading Spinner */
.spinner {
  display: inline-block; width: 18px; height: 18px;
  border: 2px solid rgba(255,255,255,0.3);
  border-top-color: #fff; border-radius: 50%;
  animation: spin 0.6s linear infinite;
  vertical-align: middle;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* Keyframes */
@keyframes fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: translateY(0); } }

/* Scrollbar */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-secondary); }

/* Responsive */
@media (max-width: 768px) {
  .hero { padding: 40px 20px 32px; }
  .hero h1 { font-size: 2rem; }
  .cards { grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); }
  .card { padding: 12px 14px; font-size: 0.85rem; }
  .tool-container { padding: 24px 18px; margin: 20px 12px; }
  .nav-tagline { display: none; }
  .form-row { flex-direction: column; gap: 0; }
  .upload-zone { padding: 24px 16px; }
}

@media (max-width: 480px) {
  .cards { grid-template-columns: 1fr 1fr; gap: 8px; }
  .hero h1 { font-size: 1.6rem; }
  .tool-header-icon { font-size: 1.6rem; }
}