*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --danger: #dc2626;
  --danger-hover: #b91c1c;
  --success: #16a34a;
  --surface: #ffffff;
  --bg: #f1f5f9;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;
  --radius: 10px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Noto Sans JP", "Hiragino Kaku Gothic ProN", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}

/* ========== Header ========== */
.site-header {
  background: linear-gradient(135deg, #1e3a5f 0%, #2563eb 100%);
  color: white;
  padding: 1rem 1rem 1.25rem;
}

.header-inner {
  max-width: 900px;
  margin: 0 auto;
}

.back-link {
  display: inline-block;
  color: rgba(255,255,255,0.8);
  text-decoration: none;
  font-size: 0.875rem;
  margin-bottom: 0.5rem;
  min-height: 44px;
  line-height: 44px;
}

.back-link:hover {
  color: #fff;
}

.site-header h1 {
  font-size: 1.2rem;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 0.25rem;
}

.subtitle {
  font-size: 0.85rem;
  opacity: 0.85;
}

/* ========== Main layout ========== */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 1rem;
}

/* ========== Ad units ========== */
.ad-unit {
  margin: 1.25rem 0;
}

/* ========== Tool sections ========== */
.tool-section {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: 0 1px 4px rgba(0,0,0,0.07);
  margin-bottom: 1rem;
}

.tool-section h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #1e3a5f;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--border);
}

.hidden {
  display: none;
}

/* ========== Upload ========== */
.drop-zone {
  border: 2px dashed #94a3b8;
  border-radius: var(--radius);
  padding: 2rem 1rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
  margin-bottom: 1.25rem;
}

.drop-zone.drag-over {
  border-color: var(--primary);
  background: #eff6ff;
}

.drop-zone-icon {
  font-size: 2.5rem;
  line-height: 1;
  margin-bottom: 0.5rem;
}

.drop-zone-text {
  font-weight: 600;
  color: #334155;
  margin-bottom: 0.25rem;
}

.drop-zone-sub {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

#file-input {
  display: none;
}

.paste-area label {
  display: block;
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 0.375rem;
  color: #334155;
}

#csv-paste {
  width: 100%;
  padding: 0.625rem 0.75rem;
  font-size: 0.875rem;
  font-family: monospace;
  border: 1px solid var(--border);
  border-radius: 6px;
  resize: vertical;
  color: var(--text);
  margin-bottom: 0.75rem;
  line-height: 1.5;
}

#csv-paste:focus {
  outline: 2px solid var(--primary);
  outline-offset: 1px;
}

/* ========== Buttons ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.375rem;
  padding: 0.75rem 1.25rem;
  font-size: 0.95rem;
  font-weight: 600;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
  min-height: 44px;
  text-decoration: none;
  white-space: nowrap;
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background: var(--primary);
  color: white;
  min-height: 56px;
  width: 100%;
}

.btn-primary:hover {
  background: var(--primary-hover);
}

.btn-secondary {
  background: #e2e8f0;
  color: #1e293b;
  min-height: 44px;
}

.btn-secondary:hover {
  background: #cbd5e1;
}

.btn-op {
  background: #f8fafc;
  color: #1e293b;
  border: 1px solid var(--border);
  min-height: 56px;
  flex-direction: column;
  gap: 0.25rem;
  padding: 0.75rem 0.5rem;
  font-size: 0.85rem;
  border-radius: 8px;
}

.btn-op:hover {
  background: #eff6ff;
  border-color: var(--primary);
  color: var(--primary);
}

.btn-danger {
  background: #fee2e2;
  color: var(--danger);
  min-height: 44px;
  border: 1px solid #fca5a5;
}

.btn-danger:hover:not(:disabled) {
  background: var(--danger);
  color: white;
}

.btn-danger:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-download {
  background: var(--success);
  color: white;
  min-height: 56px;
  width: 100%;
  font-size: 1rem;
}

.btn-download:hover {
  background: #15803d;
}

.op-icon {
  font-size: 1.2rem;
  line-height: 1;
}

/* ========== Ops panels ========== */
.ops-panel {
  margin-bottom: 1.25rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border);
}

.ops-panel:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.ops-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: #475569;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 0.75rem;
}

.ops-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.625rem;
}

/* ========== Column checkboxes ========== */
.col-checkboxes {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.col-checkbox-item {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  background: #f8fafc;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.375rem 0.625rem;
  font-size: 0.875rem;
  cursor: pointer;
  min-height: 44px;
  transition: background 0.15s;
}

.col-checkbox-item:hover {
  background: #eff6ff;
}

.col-checkbox-item input[type="checkbox"] {
  width: 16px;
  height: 16px;
  accent-color: var(--primary);
  cursor: pointer;
}

/* ========== Filter ========== */
.filter-row {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  margin-bottom: 0.625rem;
}

.filter-row label {
  font-size: 0.875rem;
  font-weight: 600;
  color: #475569;
}

.filter-row select,
.filter-row input[type="text"] {
  width: 100%;
  padding: 0.625rem 0.75rem;
  font-size: 0.95rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  background: white;
  min-height: 44px;
}

.filter-row select:focus,
.filter-row input[type="text"]:focus {
  outline: 2px solid var(--primary);
  outline-offset: 1px;
}

/* ========== Rename inputs ========== */
.rename-inputs {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.rename-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 0.5rem;
}

.rename-arrow {
  font-size: 1rem;
  color: var(--text-muted);
}

.rename-input {
  padding: 0.5rem 0.625rem;
  font-size: 0.875rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  background: white;
  min-height: 44px;
}

.rename-input:focus {
  outline: 2px solid var(--primary);
  outline-offset: 1px;
}

.rename-input.original {
  background: #f8fafc;
  color: var(--text-muted);
}

/* ========== History ========== */
.history-list {
  list-style: none;
  max-height: 160px;
  overflow-y: auto;
  border: 1px solid var(--border);
  border-radius: 6px;
  margin-bottom: 0.75rem;
}

.history-list li {
  padding: 0.5rem 0.75rem;
  font-size: 0.875rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 0.375rem;
}

.history-list li:last-child {
  border-bottom: none;
}

.history-empty {
  color: var(--text-muted);
  font-style: italic;
}

.history-badge {
  background: var(--primary);
  color: white;
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.1rem 0.4rem;
  border-radius: 100px;
  white-space: nowrap;
}

/* ========== Data info ========== */
.data-info {
  background: #eff6ff;
  border: 1px solid #bfdbfe;
  border-radius: 6px;
  padding: 0.625rem 0.875rem;
  font-size: 0.875rem;
  margin-bottom: 1rem;
  color: #1e40af;
  font-weight: 500;
}

/* ========== Status messages ========== */
.status-message {
  margin-top: 0.75rem;
  font-size: 0.875rem;
  font-weight: 600;
  min-height: 1.25rem;
}

.status-message.success {
  color: var(--success);
}

.status-message.error {
  color: var(--danger);
}

/* ========== Preview table ========== */
.preview-note {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.table-wrap {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: 8px;
}

.preview-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.preview-table th {
  background: #1e3a5f;
  color: white;
  font-weight: 600;
  padding: 0.5rem 0.75rem;
  text-align: left;
  white-space: nowrap;
  position: sticky;
  top: 0;
}

.preview-table td {
  padding: 0.4rem 0.75rem;
  border-bottom: 1px solid var(--border);
  max-width: 200px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.preview-table tr:nth-child(even) td {
  background: #f8fafc;
}

.preview-table tr:hover td {
  background: #eff6ff;
}

/* ========== Download section ========== */
.download-row {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  margin-bottom: 0.875rem;
}

.download-row label {
  font-size: 0.875rem;
  font-weight: 600;
  color: #475569;
}

#encoding-select {
  width: 100%;
  padding: 0.625rem 0.75rem;
  font-size: 0.95rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  background: white;
  min-height: 44px;
}

/* ========== Howto section ========== */
.howto-section {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.5rem 1.25rem;
  box-shadow: 0 1px 4px rgba(0,0,0,0.07);
  margin-bottom: 1rem;
}

.howto-section h2 {
  font-size: 1rem;
  font-weight: 700;
  color: #1e3a5f;
  margin-top: 1.25rem;
  margin-bottom: 0.625rem;
}

.howto-section h2:first-child {
  margin-top: 0;
}

.howto-section ol {
  padding-left: 1.25rem;
}

.howto-section li {
  font-size: 0.9rem;
  color: #475569;
  margin-bottom: 0.5rem;
}

.howto-section p {
  font-size: 0.9rem;
  color: #475569;
  line-height: 1.7;
}

/* ========== Footer ========== */
.site-footer {
  text-align: center;
  padding: 2rem 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.site-footer a {
  color: #475569;
  text-decoration: none;
}

.site-footer a:hover {
  color: var(--primary);
}

.site-footer p + p {
  margin-top: 0.375rem;
}

/* ========== Responsive ========== */
@media (min-width: 640px) {
  .site-header h1 {
    font-size: 1.5rem;
  }

  main {
    padding: 1.5rem 2rem;
  }

  .ops-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .filter-row {
    flex-direction: row;
    align-items: center;
  }

  .filter-row label {
    width: 6rem;
    flex-shrink: 0;
  }
}

@media (max-width: 400px) {
  .ops-grid {
    grid-template-columns: 1fr 1fr;
  }
}