:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --text-soft: #6b7280;
  --border: #e5e7eb;
  --border-strong: #d1d5db;
  --accent: #2563eb;
  --accent-soft: #eff6ff;
  --accent-dark: #1d4ed8;
  --danger: #dc2626;
  --ok: #16a34a;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(16,24,40,.04), 0 8px 24px rgba(16,24,40,.06);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", system-ui, -apple-system, sans-serif;
  font-size: 14px;
  line-height: 1.6;
}

/* ---------- Header ---------- */
.topbar {
  background: linear-gradient(120deg, #1e3a8a 0%, #2563eb 60%, #3b82f6 100%);
  color: #fff;
  padding: 20px 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 14px; }
.brand-icon {
  width: 42px; height: 42px; border-radius: 12px;
  background: rgba(255,255,255,.16);
  display: flex; align-items: center; justify-content: center;
}
.topbar h1 { margin: 0; font-size: 19px; font-weight: 600; letter-spacing: .3px; }
.topbar p { margin: 2px 0 0; font-size: 12.5px; color: rgba(255,255,255,.82); }
.topbar-tags { display: flex; gap: 8px; flex-wrap: wrap; }
.tag {
  font-size: 12px; padding: 4px 12px; border-radius: 999px;
  background: rgba(255,255,255,.14); border: 1px solid rgba(255,255,255,.22);
  color: #fff;
}

/* ---------- Layout ---------- */
.container {
  max-width: 1080px;
  margin: 24px auto 48px;
  padding: 0 20px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 22px;
}
.card-head { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; margin-bottom: 16px; }
.card-head h2 { margin: 0; font-size: 16px; font-weight: 600; }
.card-sub { margin: 0; flex: 1 1 100%; color: var(--text-soft); font-size: 12.5px; }
.step {
  width: 22px; height: 22px; flex: 0 0 22px;
  border-radius: 50%; background: var(--accent); color: #fff;
  font-size: 12.5px; font-weight: 600;
  display: inline-flex; align-items: center; justify-content: center;
  align-self: center;
}

/* ---------- Dropzone ---------- */
.dropzone {
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius);
  background: #fbfcfe;
  padding: 40px 20px;
  text-align: center;
  transition: all .18s ease;
  outline: none;
}
.dropzone:hover, .dropzone:focus-visible { border-color: var(--accent); background: var(--accent-soft); }
.dropzone.dragover { border-color: var(--accent); background: var(--accent-soft); transform: scale(1.005); }
.dz-icon { color: var(--accent); opacity: .85; }
.dz-title { margin: 8px 0 4px; font-size: 15px; font-weight: 600; }
.dz-hint { margin: 0 0 10px; color: var(--text-soft); font-size: 12.5px; }
.dz-tip { margin: 12px 0 0; color: #9ca3af; font-size: 12px; }

/* ---------- Buttons ---------- */
.btn {
  border: 1px solid var(--border-strong);
  background: #fff;
  color: var(--text);
  border-radius: 9px;
  padding: 7px 14px;
  font-size: 13px;
  cursor: pointer;
  transition: all .15s ease;
  display: inline-flex; align-items: center; gap: 6px;
  font-family: inherit;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn:disabled { opacity: .5; cursor: not-allowed; border-color: var(--border-strong) !important; color: var(--text-soft) !important; background: #f9fafb !important; }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--accent-dark); border-color: var(--accent-dark); color: #fff; }
.btn-lg { padding: 11px 26px; font-size: 14.5px; font-weight: 600; border-radius: 10px; }
.btn-ghost { border-color: transparent; background: transparent; color: var(--text-soft); }
.btn-ghost:hover { background: #f3f4f6; color: var(--accent); border-color: transparent; }
.btn-mini { padding: 4px 9px; font-size: 12px; border-radius: 7px; }
.btn-outline { border-color: var(--accent); color: var(--accent); }
.btn.danger { color: var(--danger); }
.btn.danger:hover { border-color: var(--danger); color: var(--danger); background: #fef2f2; }

/* ---------- Toolbar ---------- */
.toolbar {
  display: flex; justify-content: space-between; align-items: center;
  gap: 10px; flex-wrap: wrap;
  padding: 10px 12px;
  background: #f9fafb;
  border: 1px solid var(--border);
  border-radius: 10px;
  margin-bottom: 16px;
}
.toolbar-left, .toolbar-right { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; }
.counter { font-size: 13px; color: var(--text-soft); }
.counter b { color: var(--accent); font-size: 15px; }
.divider { width: 1px; height: 16px; background: var(--border-strong); margin: 0 4px; }

/* ---------- File list ---------- */
.file-list { display: flex; flex-direction: column; gap: 14px; }
.file-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fff;
  overflow: hidden;
  transition: box-shadow .15s ease, border-color .15s ease;
}
.file-card:hover { border-color: #cbd5e1; }
.file-card.dragging { opacity: .45; }
.file-card.drag-target { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(37,99,235,.12); }

.file-head {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 12px;
  background: #fbfcfe;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}
.handle {
  cursor: grab; color: #9ca3af; font-size: 15px; letter-spacing: -2px;
  user-select: none; padding: 0 2px;
}
.handle:active { cursor: grabbing; }
.file-title { display: flex; flex-direction: column; min-width: 140px; flex: 1 1 200px; }
.file-name { font-weight: 600; font-size: 13.5px; word-break: break-all; }
.file-meta { color: var(--text-soft); font-size: 12px; }
.file-actions { display: flex; gap: 5px; flex-wrap: wrap; align-items: center; }
.range-input {
  width: 132px; padding: 4px 8px; font-size: 12px;
  border: 1px solid var(--border-strong); border-radius: 7px;
  font-family: inherit; color: var(--text);
}
.range-input:focus { outline: none; border-color: var(--accent); }
.collapse {
  border: none; background: transparent; color: var(--text-soft);
  cursor: pointer; font-size: 12.5px; font-family: inherit; padding: 4px 6px;
}
.collapse:hover { color: var(--accent); }

.pages {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(118px, 1fr));
  gap: 12px;
  padding: 14px 12px;
}
.pages.collapsed { display: none; }

.page-item {
  border: 2px solid var(--border);
  border-radius: 10px;
  background: #fff;
  cursor: pointer;
  padding: 6px;
  position: relative;
  transition: all .13s ease;
  user-select: none;
}
.page-item:hover { border-color: #93c5fd; transform: translateY(-1px); }
.page-item.selected { border-color: var(--accent); background: var(--accent-soft); }
.page-canvas {
  width: 100%;
  height: auto;
  display: block;
  background: #fff;
  border-radius: 6px;
}
.page-num {
  display: block; text-align: center; font-size: 11.5px; color: var(--text-soft);
  padding-top: 4px;
}
.page-item.selected .page-num { color: var(--accent); font-weight: 600; }
.page-check {
  position: absolute; top: 10px; right: 10px;
  width: 20px; height: 20px; border-radius: 50%;
  background: #fff; border: 1.5px solid var(--border-strong);
  display: flex; align-items: center; justify-content: center;
  color: transparent; font-size: 12px; font-weight: 700;
}
.page-item.selected .page-check { background: var(--accent); border-color: var(--accent); color: #fff; }
.page-item.loading .page-canvas { background: #f3f4f6; }

.file-error {
  margin: 0 12px 12px; padding: 10px 12px;
  background: #fef2f2; border: 1px solid #fecaca; color: #b91c1c;
  border-radius: 8px; font-size: 12.5px;
}

/* ---------- Merge row ---------- */
.merge-row { display: flex; gap: 14px; align-items: flex-end; flex-wrap: wrap; }
.field { display: flex; flex-direction: column; gap: 6px; flex: 1 1 260px; }
.field-label { font-size: 12.5px; color: var(--text-soft); }
.field input[type="text"] {
  padding: 10px 12px; font-size: 14px; font-family: inherit;
  border: 1px solid var(--border-strong); border-radius: 10px; color: var(--text);
}
.field input[type="text"]:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px rgba(37,99,235,.1); }

.progress { margin-top: 16px; }
.progress-bar { height: 8px; background: #eef2f7; border-radius: 999px; overflow: hidden; }
.progress-inner { height: 100%; width: 0%; background: var(--accent); border-radius: 999px; transition: width .2s ease; }
.progress-text { display: block; margin-top: 6px; font-size: 12.5px; color: var(--text-soft); }

.result {
  margin-top: 18px; padding: 14px 16px;
  border: 1px solid #bbf7d0; background: #f0fdf4; border-radius: 12px;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
}
.result-icon { width: 40px; height: 40px; border-radius: 50%; background: #dcfce7; color: var(--ok); display: flex; align-items: center; justify-content: center; }
.result-info { flex: 1 1 200px; }
.result-name { margin: 0; font-weight: 600; font-size: 14px; }
.result-meta { margin: 2px 0 0; font-size: 12.5px; color: var(--text-soft); white-space: pre-line; }

/* ---------- Tips ---------- */
.tips h3 { margin: 0 0 10px; font-size: 14px; }
.tips ul { margin: 0; padding-left: 20px; color: var(--text-soft); font-size: 13px; }
.tips li { margin-bottom: 6px; }
.tips code { background: #f3f4f6; padding: 1px 6px; border-radius: 5px; color: var(--accent); font-size: 12.5px; }
.inline-icon { color: var(--text); letter-spacing: -2px; }

.footer { text-align: center; color: #9ca3af; font-size: 12px; padding: 0 20px 32px; }

/* ---------- Toast ---------- */
.toast {
  position: fixed; left: 50%; bottom: 34px; transform: translateX(-50%);
  background: #111827; color: #fff; padding: 11px 20px; border-radius: 10px;
  font-size: 13px; box-shadow: 0 10px 30px rgba(0,0,0,.2); z-index: 999;
  max-width: 90vw; text-align: center;
}
.toast.error { background: #b91c1c; }

.hidden { display: none !important; }

.empty-hint {
  text-align: center; color: var(--text-soft); padding: 26px 10px; font-size: 13px;
}

@media (max-width: 640px) {
  .topbar { padding: 16px 18px; }
  .container { padding: 0 14px; margin-top: 18px; }
  .card { padding: 16px; }
  .pages { grid-template-columns: repeat(auto-fill, minmax(96px, 1fr)); gap: 10px; }
  .merge-row { flex-direction: column; align-items: stretch; }
  .btn-lg { justify-content: center; }
}