body { font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Kaku Gothic Pro", Meiryo, sans-serif; line-height: 1.6; color: #333; margin: 0; }
    header, footer, .container { max-width: 1000px; margin: 0 auto; padding: 0 15px; }
    header { background: #fff; padding: 20px 0; border-bottom: 3px solid #0ccda1; }
    nav ul { display: flex; list-style: none; padding: 0; gap: 20px; background: #0ccda1; padding: 10px; border-radius: 5px; }
    nav a { color: #fff; text-decoration: none; font-weight: bold; }
    #top_main { background: #f0f8ff; padding: 40px 0; text-align: center; }
    .hero-placeholder { width: 100%; height: 300px; background: linear-gradient(135deg, #0ccda1, #51b0f9); display: flex; align-items: center; justify-content: center; color: white; font-size: 2rem; }
    .topics { display: flex; gap: 20px; padding: 40px 0; flex-wrap: wrap; }
    .topics_box { flex: 1; min-width: 300px; border: 1px solid #ccc; padding: 20px; text-align: center; }
    footer { background: #333; color: #fff; padding: 40px 0; margin-top: 40px; }
    .info-icon { display: inline-block; width: 40px; height: 10px; background: #4caf50; margin-right: 10px; }
    .footer-links { display: flex; justify-content: space-around; flex-wrap: wrap; }
    @media (max-width: 768px) { nav ul { flex-direction: column; } .topics { flex-direction: column; } }