.back-to-top { position: fixed; bottom: 20px; right: 20px; background-color: #ffff00; color: #ffffff; /* 常に白文字で視認性を確保 */ padding: 10px 15px; border-radius: 5px; text-decoration: none; font-weight: bold; box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2); } .back-to-top:hover { background-color: #005b99; color…