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

body {
    font-family: 'Helvetica Neue', Arial, 'Hiragino Kaku Gothic ProN', Meiryo, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f9f9f9;
    padding: 20px;
    max-width: 900px;
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 40px;
    padding: 20px 0;
    border-bottom: 1px solid #eaeaea;
}

h1 {
    font-size: 2.5rem;
    color: #2c3e50;
}

.intro {
    text-align: center;
    margin-bottom: 40px;
    font-size: 1.2rem;
}

.portfolio-links {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 30px;
    margin-bottom: 40px;
}

.card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    padding: 25px;
    width: 100%;
    max-width: 400px;
    text-align: center;
    transition: transform 0.3s ease;
}

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

h2 {
    color: #3498db;
    margin-bottom: 15px;
}

.card p {
    margin-bottom: 20px;
    color: #666;
}

.btn {
    display: inline-block;
    background-color: #3498db;
    color: white;
    text-decoration: none;
    padding: 10px 20px;
    border-radius: 5px;
    font-weight: bold;
    transition: background-color 0.3s ease;
}

.btn:hover {
    background-color: #2980b9;
}

footer {
    text-align: center;
    margin-top: 40px;
    padding: 20px 0;
    color: #888;
    font-size: 0.9rem;
    border-top: 1px solid #eaeaea;
}

@media (max-width: 768px) {
    .portfolio-links {
        flex-direction: column;
        align-items: center;
    }
}