header {
    position: fixed;
    top: 0;
    width: 100%;
    color: white;
    z-index: 1000;
    min-width: 200px;
}

.top {
    background-color: #004080;
    color: white;
    display: flex;
    padding: 10px 20px;
    justify-content: space-between;
    align-items: center;
}

.logo-link {
    display: inline-flex;
    align-items: center;
    text-decoration: none;
}

.logo {
    height: 50px;
    width: auto;
    display: block;
}

.navbar {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    gap: 4px;
}

.navbar a {
    color: white;
    text-decoration: none;
    padding: 14px 18px;
    border-radius: 4px;
    transition: background-color 0.2s ease;
}

.navbar a:hover,
.navbar a:focus-visible {
    background-color: #003060;
    outline: none;
}

.navbar a:focus-visible {
    box-shadow: 0 0 0 2px #ffffff inset;
}

/* ハンバーガー */
.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: space-between;
    width: 32px;
    height: 26px;
    background: transparent;
    border: 0;
    cursor: pointer;
    padding: 0;
}

.nav-toggle span {
    display: block;
    height: 3px;
    width: 100%;
    background: #ffffff;
    border-radius: 2px;
    transition: transform 0.25s ease, opacity 0.2s ease;
}

.nav-toggle.open span:nth-child(1) {
    transform: translateY(11px) rotate(45deg);
}
.nav-toggle.open span:nth-child(2) {
    opacity: 0;
}
.nav-toggle.open span:nth-child(3) {
    transform: translateY(-11px) rotate(-45deg);
}

main {
    max-width: 800px;
    margin: 0 auto;
    line-height: 1.8;
    padding-top: 90px;
}

@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }
    .navbar {
        position: absolute;
        top: 100%;
        right: 0;
        left: 0;
        background-color: #004080;
        flex-direction: column;
        align-items: stretch;
        gap: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease;
    }
    .navbar.open {
        max-height: 400px;
    }
    .navbar a {
        padding: 16px 20px;
        border-top: 1px solid rgba(255, 255, 255, 0.15);
        border-radius: 0;
    }
}