body {
    display: flex;
    flex-direction: column;
    align-items: center;
    font-family: Arial, sans-serif;
    background-color: #f0f8ff;
    margin: 0;
    padding: 20px;
}


table#sigma {
    border: 2px solid #333;
    margin-bottom: 20px;
}
td {
    border: 2px solid #333;
    margin-bottom: 20px;
}

nav {
    margin-top: 20px;
    background-color: #1f2933;
    padding: 12px 20px;
    border-radius: 6px;
    display: inline-block;
}


nav a {
    color: #ffffff;
    text-decoration: none;
    margin-right: 20px;
    font-size: 18px;
    font-family: Arial, sans-serif;
    font-weight: 500;
}


nav a:hover {
    color: #38bdf8;
    text-decoration: underline;
}


nav a:active {
    color: #0ea5e9;
}