body {
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f4f9fc;
    color: #1c1c1c;
    line-height: 1.6;
}
header {
    background-color: #1e3a8a;
    color: #ffffff;
    padding: 40px 20px;
    text-align: center;
}
.subtitle {
    font-size: 1.2em;
    margin-top: 10px;
}
main {
    padding: 40px 20px;
    max-width: 900px;
    margin: auto;
}
.letter, .index-section {
    background: white;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}
footer {
    background-color: #e0e7ff;
    text-align: center;
    padding: 20px;
    font-size: 0.85em;
    color: #333;
    border-top: 1px solid #c7d2fe;
}
.disclaimer {
    max-width: 900px;
    margin: auto;
    line-height: 1.4;
}
.start-button {
    text-align: center;
    margin-top: 30px;
}
.button {
    display: inline-block;
    background-color: #1e3a8a;
    color: white;
    padding: 12px 24px;
    text-decoration: none;
    font-size: 1.1em;
    border-radius: 8px;
    transition: background-color 0.3s ease;
}
.button:hover {
    background-color: #3b5bcc;
}
.index-list {
    list-style: none;
    padding: 0;
    font-size: 1.1em;
}
.index-list li {
    margin: 15px 0;
    padding: 10px;
    background-color: #e0e7ff;
    border-radius: 8px;
    transition: background-color 0.3s ease;
}
.index-list li:hover {
    background-color: #c7d2fe;
}
.index-list a {
    text-decoration: none;
    color: #1e3a8a;
    font-weight: 600;
}