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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fafafa;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

header {
    background-color: #1a1a1a;
    color: #fff;
    padding: 3rem 0;
    text-align: center;
    margin-bottom: 3rem;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

.subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
    font-weight: 300;
}

main {
    margin-bottom: 4rem;
}

.intro {
    background-color: #fff;
    padding: 2rem;
    border-radius: 8px;
    margin-bottom: 3rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    text-align: center;
    font-size: 1.1rem;
    color: #555;
}

.letters {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.letter {
    background-color: #fff;
    padding: 2.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    transition: box-shadow 0.3s ease;
}

.letter:hover {
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.letter h2 {
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
    color: #1a1a1a;
    border-bottom: 2px solid #e0e0e0;
    padding-bottom: 0.5rem;
}

.letter .date {
    color: #666;
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
    font-style: italic;
}

.letter-content {
    font-size: 1.05rem;
    line-height: 1.8;
    color: #444;
}

.letter-content p {
    margin-bottom: 1.2rem;
}

.letter-content p:last-child {
    margin-bottom: 0;
}

.letter-content ul {
    margin: 1.2rem 0;
    padding-left: 2rem;
    list-style-type: disc;
}

.letter-content li {
    margin-bottom: 0.15rem;
    line-height: 1.6;
}

.letter-content li:last-child {
    margin-bottom: 0;
}

footer {
    background-color: #1a1a1a;
    color: #fff;
    text-align: center;
    padding: 2rem 0;
    margin-top: 4rem;
}

footer p {
    opacity: 0.8;
    font-size: 0.9rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .letter {
        padding: 1.5rem;
    }

    .letter h2 {
        font-size: 1.5rem;
    }

    .letter-content {
        font-size: 1rem;
    }
}