@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@400;700&display=swap');

body {
    font-family: 'Noto Sans JP', sans-serif;
    background-color: #f4f7f6;
    color: #333;
    margin: 0;
    padding: 0;
    line-height: 1.8;
}

header {
    background: linear-gradient(135deg, #566573, #2c3e50);
    color: white;
    padding: 60px 20px;
    text-align: center;
}

header h1 img {
    border-radius: 50%;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    transition: transform 0.3s ease;
}

header h1 img:hover {
    transform: scale(1.1);
}

.navbar {
    background-color: #ffffff;
    border-bottom: 1px solid #e0e0e0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}

.navbar ul {
    display: flex;
    justify-content: center;
    list-style: none;
    margin: 0;
    padding: 0;
}

.navbar ul li {
    margin: 0;
}

.navbar ul li a {
    display: block;
    color: #555;
    padding: 15px 25px;
    text-decoration: none;
    font-weight: 700;
    transition: color 0.3s, background-color 0.3s;
}

.navbar ul li a:hover, .navbar ul li a.active {
    color: #1a73e8;
    background-color: #f0f4f8;
}

main {
    max-width: 800px;
    margin: 40px auto;
    padding: 0 20px;
}

.card {
    background-color: white;
    border-radius: 12px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.08);
    padding: 30px;
    margin-bottom: 30px;
    transition: box-shadow 0.3s ease;
}

.card:hover {
    box-shadow: 0 8px 25px rgba(0,0,0,0.12);
}

.card h2 {
    border-bottom: 2px solid #1a73e8;
    padding-bottom: 10px;
    margin-top: 0;
    color: #2c3e50;
}

a {
    color: #1a73e8;
    text-decoration: none;
    font-weight: 600;
}

a:hover {
    text-decoration: underline;
}

footer {
    text-align: center;
    color: #888;
    padding: 30px 20px;
    font-size: 14px;
    background-color: #e9ecef;
    margin-top: 40px;
}

img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
}

/* 既存の.math-boxスタイルも残しつつ、微調整 */
.math-box {
    background-color: #f9f9f9;
    border-left: 4px solid #1a73e8;
    padding: 15px;
    margin: 20px 0;
    border-radius: 6px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.math-box p {
    margin: 0 0 10px 0;
    font-weight: bold;
}


@media (max-width: 600px) {
    body {
        font-size: 16px;
    }

    header {
        padding: 40px 15px;
    }

    .navbar ul {
        flex-direction: column;
        text-align: center;
    }

    main {
        margin: 20px 10px;
    }

    .card {
        padding: 20px;
    }
}