body {
    font-family: Arial, sans-serif;
    background-color: #f0f2f5;
    margin: 0;
    padding: 20px;
    text-align: center;
}
header {
    margin-bottom: 30px;
}
main {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
}
.tarjeta {
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    width: 200px;
}
.tarjeta h2 {
    margin-top: 0;
}
a {
    display: inline-block;
    background-color: #007bff;
    color: white;
    padding: 10px 20px;
    text-align: center;
    text-decoration: none;
    border-radius: 5px;
    font-weight: bold;
}
a:hover {
    background-color: #0056b3;
}
footer {
    margin-top: 5px;
    font-size: 0.9em;
    color: #666;
}