body {
    font-family: 'Yu Gothic', 'Hiragino Kaku Gothic Pro', Meiryo, sans-serif;
    line-height: 1.6;
    max-width: 720px;
    margin: 40px auto;
    padding: 0 20px;
    background: #fafafa;
    color: #333;
}
h1, h2, h3 {
    color: #2c3e50;
}
h1 {
    font-size: 2.4rem;
    margin-bottom: 1rem;
    text-align: center;
}
h2 {
    font-size: 1.8rem;
    margin-top: 2.5rem;
    border-bottom: 2px solid #2980b9;
    padding-bottom: 0.3rem;
}
h3 {
    font-size: 1.3rem;
    margin-top: 1.8rem;
}
p {
    margin: 1rem 0;
    font-size: 1.1rem;
}
nav {
    background: #2980b9;
    padding: 1rem 1.2rem;
    border-radius: 8px;
    margin-bottom: 2rem;
}
nav h2 {
    color: #fff;
    margin: 0 0 0.8rem 0;
    font-size: 1.3rem;
}
nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
}
nav ul li {
    margin-bottom: 0.5rem;
}
nav ul li a {
    color: #ecf0f1;
    text-decoration: none;
    font-weight: bold;
    transition: color 0.3s ease;
}
nav ul li a:hover {
    color: #f39c12;
}
footer {
    margin-top: 4rem;
    text-align: center;
    color: #666;
    font-size: 0.9rem;
}
/* スムーススクロール用 */
html {
    scroll-behavior: smooth;
}