:root {
    --primary-color: #357AE8;
    --secondary-color: #1565c0;
    --background-color: #ffffff;
    --text-color: #333;
    --white: #ffffff;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans SC', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

header {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 2rem 0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    text-align: center;
}

.header-content h1 {
    font-size: 2.5rem;
    font-weight: 700;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
    background-color: transparent;
}

.module-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
    background-color: transparent;
}

.module-card {
    background-color: var(--white);
    border-radius: 10px;
    padding: 2rem;
    text-decoration: none;
    color: var(--text-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.module-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}

.card-content {
    text-align: center;
}

.card-content h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.card-content p {
    color: #666;
}

footer {
    padding: 1.5rem 0;
    margin-top: 3rem;
    background-color: transparent;
    border: none;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    text-align: center;
}

.back-button {
    position: fixed;
    top: 20px;
    left: 20px;
    background-color: var(--primary-color);
    color: white;
    padding: 15px 30px;
    border-radius: 7.5px;
    text-decoration: none;
    font-weight: 500;
    font-size: 1.5rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    transition: background-color 0.3s ease;
    z-index: 1000;
}

.back-button:hover {
    background-color: var(--secondary-color);
}

@media (max-width: 768px) {
    html, body {
        overflow-x: hidden;
    }
    .header-content h1 {
        font-size: 1.3rem;
    }
    header {
        padding: 1rem 0;
    }
    .container {
        padding: 0.5rem;
    }
    .module-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
        margin-top: 1rem;
    }
    .module-card {
        padding: 1rem;
        border-radius: 7px;
        font-size: 0.98rem;
    }
    .card-content h2 {
        font-size: 1.1rem;
        margin-bottom: 0.5rem;
    }
    .back-button {
        padding: 8px 14px;
        font-size: 0.98rem;
        top: 10px;
        left: 10px;
        border-radius: 4px;
    }
    .small-back-button {
        padding: 2px 4px;
        font-size: 0.25rem;
        border-radius: 2px;
        top: 33vh;
    }
}

@media (max-width: 400px) {
    .header-content h1 {
        font-size: 1rem;
    }
    .module-card {
        padding: 0.7rem;
        font-size: 0.92rem;
    }
    .back-button {
        padding: 6px 10px;
        font-size: 0.9rem;
    }
    .small-back-button {
        padding: 1.5px 2.5px;
        font-size: 0.18rem;
        border-radius: 1px;
        top: 33vh;
    }
}

.notice-tip {
    max-width: 600px;
    margin: 20px auto 0 auto;
    background: #fffbe6;
    color: #b08500;
    border-radius: 8px;
    padding: 10px 18px;
    font-size: 0.98rem;
    text-align: center;
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
    letter-spacing: 1px;
}