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

body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f7fa;
}

header {
    background-color: #2c3e50;
    color: white;
    padding: 1rem 0;
    text-align: center;
}

nav ul {
    display: flex;
    justify-content: center;
    list-style: none;
    padding: 1rem 0;
}

nav li {
    margin: 0 1rem;
}

nav a {
    color: white;
    text-decoration: none;
    font-weight: bold;
    transition: color 0.3s;
}

nav a:hover {
    color: #3498db;
}

main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

section {
    margin-bottom: 3rem;
    background-color: white;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

h2 {
    font-size: 2rem;
    color: #2c3e50;
    margin-bottom: 1.5rem;
    border-bottom: 2px solid #ecf0f1;
    padding-bottom: 0.5rem;
}

h3 {
    font-size: 1.5rem;
    color: #3498db;
    margin-bottom: 1rem;
}

p {
    margin-bottom: 1rem;
}

.info-container {
    display: flex;
    flex-wrap: wrap;
    gap: 2rem;
    margin-top: 1.5rem;
}

.info-card {
    flex: 1 1 45%;
    padding: 1.5rem;
    border-radius: 8px;
    background-color: #f8f9fa;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.domain-example {
    font-size: 1.5rem;
    text-align: center;
    padding: 1rem;
    margin-top: 1rem;
    background-color: #ecf0f1;
    border-radius: 4px;
}

.subdomain {
    color: #e67e22;
}

.second-level {
    color: #3498db;
}

.tld {
    color: #2ecc71;
}

.tld-container {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.tld-card {
    flex: 1 1 30%;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s;
}

.tld-card:hover {
    transform: translateY(-5px);
}

#gtld {
    background-color: #e8f4fd;
    border-left: 4px solid #3498db;
}

#cctld {
    background-color: #eafaf1;
    border-left: 4px solid #2ecc71;
}

#newtld {
    background-color: #fef5e7;
    border-left: 4px solid #e67e22;
}

ol, ul {
    padding-left: 2rem;
    margin-bottom: 1.5rem;
}

.registrar-examples {
    background-color: #f8f9fa;
    padding: 1.5rem;
    border-radius: 8px;
    margin-top: 1.5rem;
}

.quiz-container {
    background-color: #f8f9fa;
    padding: 2rem;
    border-radius: 8px;
    margin-top: 1.5rem;
}

#question {
    font-size: 1.2rem;
    font-weight: bold;
    margin-bottom: 1.5rem;
}

#options {
    display: flex;
    flex-direction: column;
    gap: 0.8rem;
    margin-bottom: 1.5rem;
}

.option {
    padding: 0.8rem;
    background-color: white;
    border: 1px solid #ddd;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.option:hover {
    background-color: #ecf0f1;
}

.selected {
    background-color: #d6eaf8;
    border-color: #3498db;
}

#submit-answer, #next-question {
    padding: 0.8rem 1.5rem;
    background-color: #3498db;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: bold;
    transition: background-color 0.3s;
}

#submit-answer:hover, #next-question:hover {
    background-color: #2980b9;
}

#result {
    margin-top: 1.5rem;
    padding: 1rem;
    border-radius: 4px;
}

.correct {
    background-color: #d5f5e3;
    color: #27ae60;
}

.incorrect {
    background-color: #fadbd8;
    color: #e74c3c;
}

footer {
    text-align: center;
    padding: 2rem;
    background-color: #2c3e50;
    color: white;
}

/* レスポンシブデザイン */
@media (max-width: 768px) {
    nav ul {
        flex-direction: column;
        gap: 0.5rem;
    }
    
    .info-container, .tld-container {
        flex-direction: column;
    }
    
    .info-card, .tld-card {
        flex: 1 1 100%;
    }
}