body {
    font-family: "Helvetica Neue", Arial, sans-serif;
    line-height: 1.7;
    margin: 0;
    padding: 0;
    background: #fafafa;
    color: #333;
    font-size: 16px;
}

header {
    background: #004466;
    color: #fff;
    padding: 1.5em 1em;
    text-align: center;
}

header h1 {
    margin: 0;
    font-size: 2em;
}

header p {
    margin: 0.3em 0 0;
    font-size: 1em;
}

.lang-switch {
    text-align: right;
    margin: 0.5em 1em;
    font-size: 0.9em;
}

.lang-switch a {
    margin-left: 0.5em;
    text-decoration: none;
    color: #004466;
}

nav {
    text-align: center;
    background: #eee;
    padding: 0.8em;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    gap: 1.5em;
}

nav a {
    text-decoration: none;
    color: #004466;
    font-weight: bold;
}

/* ハンバーガーアイコン */
.menu-toggle {
    display: none;
    cursor: pointer;
    font-size: 1.8em;
    background: none;
    border: none;
    color: #004466;
}

main {
    max-width: 900px;
    margin: 2em auto;
    padding: 0 1em;
}

section {
    margin-bottom: 2.5em;
}

h2 {
    border-bottom: 2px solid #004466;
    padding-bottom: 0.3em;
    color: #004466;
    font-size: 1.4em;
}

footer {
    text-align: center;
    padding: 1em;
    background: #eee;
    font-size: 0.9em;
    color: #555;
    margin-top: 2em;
}

/* ===== スマホ対応 (768px以下) ===== */
@media (max-width: 768px) {
    body {
        font-size: 17px;
    }

    header h1 {
        font-size: 1.5em;
    }

    header p {
        font-size: 0.9em;
    }

    nav {
        text-align: left;
        padding: 0.5em 1em;
    }

    nav ul {
        flex-direction: column;
        align-items: flex-start;
        display: none;
        /* 初期状態は非表示 */
    }

    nav ul.active {
        display: flex;
        /* ボタンを押したら表示 */
    }

    .menu-toggle {
        display: block;
        margin-left: auto;
    }

    main {
        margin: 1em auto;
        padding: 0 1em;
    }

    h2 {
        font-size: 1.2em;
    }
}