.back-link-bar { max-width: 1000px; margin: 0 auto; padding: 24px 20px 0; }
.back-link { display: inline-flex; align-items: center; gap: 6px; color: #2563eb; text-decoration: none; font-weight: 600; }
.back-link:hover { text-decoration: underline; }
body { margin: 0; font-family: Arial, Helvetica, sans-serif; background: #f4f7fb; color: #1f2937; }
.container { max-width: 900px; margin: 0 auto; padding: 32px 20px; }
header { margin-bottom: 24px; }
header h1 { margin: 0 0 8px; font-size: 2rem; }
header p { margin: 0; color: #4b5563; }
.seo-content { margin-bottom: 20px; padding: 16px 18px; background: #fff; border-radius: 12px; box-shadow: 0 10px 30px rgba(0,0,0,0.08); }
.seo-content h2 { margin: 0 0 8px; font-size: 1.2rem; }
.seo-content p { margin: 0; line-height: 1.6; color: #4b5563; }
.tool-box { background: #fff; border-radius: 12px; padding: 20px; box-shadow: 0 10px 30px rgba(0,0,0,0.08); }
.form-group { display: flex; flex-direction: column; margin-bottom: 16px; }
.form-group label { font-weight: 600; margin-bottom: 6px; }
.io-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
@media (max-width: 640px) { .io-grid { grid-template-columns: 1fr; } }
.actions { display: flex; gap: 12px; flex-wrap: wrap; margin-bottom: 20px; }
button { border: none; border-radius: 8px; padding: 10px 16px; cursor: pointer; font-weight: 600; background: #2563eb; color: #fff; transition: background 0.2s; }
button:hover { background: #1d4ed8; }
textarea, input[type="text"], input[type="number"], select { padding: 12px; border: 1px solid #d1d5db; border-radius: 8px; font-size: 1rem; width: 100%; box-sizing: border-box; font-family: inherit; }
textarea { resize: vertical; font-family: monospace; }
.status { margin-top: 16px; padding: 10px 12px; border-radius: 8px; background: #eff6ff; color: #1d4ed8; }
.status.success { background: #ecfdf3; color: #047857; }
.status.error { background: #fef2f2; color: #b91c1c; }
.site-footer { margin-top: 24px; padding: 16px 0; text-align: center; color: #6b7280; font-size: 0.95rem; }
.checkbox-row { display: flex; align-items: center; gap: 8px; cursor: pointer; margin-bottom: 8px; }
.checkbox-row input { width: auto; }
.diff-add { background: #d1fae5; color: #065f46; }
.diff-del { background: #fee2e2; color: #991b1b; text-decoration: line-through; }
.diff-same { background: transparent; }