:root {
  --primary: #4a90e2;
  --primary-hover: #357abd;
  --bg-light: #f4f7f9;
  --card-bg: #ffffff;
  --text-main: #333333;
  --text-muted: #666666;
  --border: #e1e8ed;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --accent: #ff6b6b;
}

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

body {
  font-family: 'Noto Sans JP', sans-serif;
  background-color: var(--bg-light);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 60px 20px;
}

.container {
  max-width: 720px;
  width: 100%;
}

header {
  text-align: center;
  margin-bottom: 48px;
}

h1 {
  font-size: 2.2rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 12px;
  color: var(--text-main);
}

.subtitle {
  color: var(--text-muted);
  font-size: 1rem;
  font-weight: 400;
}

.card {
  background: var(--card-bg);
  border-radius: 16px;
  padding: 40px;
  box-shadow: var(--shadow);
  margin-bottom: 32px;
  border: 1px solid var(--border);
}

.drop-zone {
  border: 2px dashed var(--border);
  border-radius: 12px;
  padding: 50px 20px;
  text-align: center;
  transition: all 0.2s ease;
  cursor: pointer;
  position: relative;
  margin-bottom: 24px;
  background: #fafbfc;
}

.drop-zone:hover,
.drop-zone.drag-over {
  border-color: var(--primary);
  background: #f0f7ff;
}

.drop-zone__icon {
  font-size: 40px;
  margin-bottom: 12px;
  display: block;
  color: var(--primary);
}

.drop-zone__text {
  color: var(--text-main);
  font-size: 1rem;
  font-weight: 500;
}

.drop-zone__subtext {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 8px;
  display: block;
}

.drop-zone__input {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}

.config-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}

.config-field {
  background: #f8fafc;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
}

.config-field label {
  display: block;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 8px;
}

.config-field input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 1rem;
  color: var(--text-main);
  background: #fff;
}

.config-field input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(74, 144, 226, 0.12);
}

.advanced-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 24px;
  user-select: none;
  transition: color 0.2s ease;
}

.advanced-toggle:hover {
  color: var(--primary);
}

.advanced-toggle svg {
  transition: transform 0.3s ease;
}

.advanced-toggle.open svg {
  transform: rotate(180deg);
}

.advanced-container {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out, opacity 0.3s ease-out;
  opacity: 0;
}

.advanced-container.open {
  max-height: 500px;
  opacity: 1;
  margin-bottom: 24px;
}

.encoding-field {
  background: #f8fafc;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-top: -8px; /* config-gridとの調整 */
  margin-bottom: 24px;
}

.encoding-field label {
  display: block;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 12px;
}

.encoding-options {
  display: flex;
  gap: 8px;
}

.encoding-btn {
  flex: 1;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
}

.encoding-btn:hover {
  background: #f1f5f9;
  border-color: #cbd5e0;
}

.encoding-btn.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.config-help {
  margin-top: 8px;
  color: var(--text-muted);
  font-size: 0.8rem;
}

.btn-container {
  text-align: center;
}

.btn-convert {
  background-color: var(--primary);
  color: white;
  border: none;
  padding: 14px 40px;
  border-radius: 8px;
  font-size: 1.05rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s ease;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  justify-content: center;
}

.btn-convert:hover:not(:disabled) {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

.btn-convert:disabled {
  background-color: #cbd5e0;
  cursor: not-allowed;
}

.status-area {
  background: #f8fafc;
  border-radius: 12px;
  padding: 20px;
  border: 1px solid var(--border);
  margin-top: 32px;
}

.status-label {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-muted);
  margin-bottom: 8px;
  display: block;
}

.status-content {
  font-size: 0.95rem;
  white-space: pre-wrap;
  color: var(--text-main);
}

.error-text {
  color: #e53e3e;
  font-weight: 500;
}

.success-text {
  color: #38a169;
  font-weight: 500;
}

h3 {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 4px;
  font-weight: 500;
}

p {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-main);
}

.loader {
  width: 18px;
  height: 18px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-bottom-color: #fff;
  border-radius: 50%;
  display: inline-block;
  animation: rotation 0.8s linear infinite;
}

@keyframes rotation {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.file-selected .drop-zone {
  border-color: var(--primary);
  background: #f0f7ff;
}

.preview-area {
  background: #f8fafc;
  border-radius: 12px;
  padding: 20px;
  border: 1px solid var(--border);
  margin-top: 24px;
}

.preview-header {
  margin-bottom: 12px;
}

.preview-table-wrap {
  overflow-x: auto;
}

.preview-table {
  width: 100%;
  border-collapse: collapse;
  table-layout: fixed;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

.preview-table th,
.preview-table td {
  border-bottom: 1px solid var(--border);
  padding: 12px;
  text-align: left;
  vertical-align: top;
  font-size: 0.9rem;
  word-break: break-word;
}

.preview-table th {
  background: #f1f5f9;
  color: var(--text-main);
  font-weight: 700;
}

.preview-table tr:last-child td {
  border-bottom: none;
}

.preview-table th:nth-child(1),
.preview-table td:nth-child(1) {
  width: 64px;
  white-space: nowrap;
}

.preview-before {
  color: var(--text-main);
}

.preview-after {
  color: var(--primary-hover);
  font-weight: 700;
}

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

@media (max-width: 640px) {
  body {
    padding: 32px 16px;
  }

  .card {
    padding: 24px;
  }

  .config-grid {
    grid-template-columns: 1fr;
  }
}