/* モダンでシンプルなデザイン */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.7;
    color: #333;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    min-height: 100vh;
    margin: 0;
    padding: 0;
}

main {
    padding: 2rem 1rem;
    min-height: calc(100vh - 120px);
}

article {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    border-radius: 16px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    padding: 3rem 2.5rem;
    margin-top: 2rem;
    margin-bottom: 2rem;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: #2d3748;
    margin: 0 0 1rem 0;
    text-align: center;
    position: relative;
    padding-bottom: 1rem;
}

h1::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, #667eea 0%, #764ba2 100%);
    border-radius: 2px;
}

h2 {
    font-size: 1.5rem;
    font-weight: 600;
    color: #4a5568;
    margin: 2.5rem 0 1rem 0;
    padding-left: 1rem;
    border-left: 4px solid #667eea;
    background: #f7fafc;
    padding: 0.75rem 1rem;
    /* border-radius: 8px; */
}

p {
    margin: 1rem 0;
    color: #4a5568;
    font-size: 1rem;
}

ol {
    margin: 1rem 0;
    padding-left: 1em;
}

ol li {
    counter-increment: item;
    position: relative;
}


strong {
    color: #2d3748;
    font-weight: 600;
}

a {
    color: #667eea;
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s ease;
}

a:hover {
    color: #764ba2;
    text-decoration: underline;
}

.footer {
    background: #2d3748;
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    margin-top: 2rem;
}

.footer a {
    color: #a0aec0;
    margin: 0 0.5rem;
    transition: color 0.2s ease;
}

.footer a:hover {
    color: white;
}

/* レスポンシブデザイン */
@media (max-width: 768px) {
    article {
        margin: 1rem;
        padding: 2rem 1.5rem;
        border-radius: 12px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.25rem;
    }
    
    main {
        padding: 1rem 0.5rem;
    }
}