body {
    font-family: Arial, sans-serif;
    margin: 0;
    background-color: #f5f5f5;
}

/* Navigation area */
.navigation {
    width: 80%;
    margin: 40px auto;
    position: relative;

    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Line behind the icons */
.navigation::before {
    content: "";
    position: absolute;

    left: 0;
    right: 0;

    top: 50%;

    height: 3px;
    background-color: #777;

    z-index: 0;
}

/* Icon links */
.navigation a {
    width: 45px;
    height: 45px;

    background-color: white;
    border: 3px solid #555;
    border-radius: 50%;

    display: flex;
    justify-content: center;
    align-items: center;

    text-decoration: none;

    font-size: 22px;

    color: black;

    position: relative;
    z-index: 1;

    transition: 0.3s;
}

/* Mouse over */
.navigation a:hover {
    background-color: #ddd;
    transform: scale(1.15);
}

/* Current page */
.navigation a.active {
    background-color: #333;
    color: white;
}

/* Page content */
.content {
    width: 80%;
    margin: 60px auto;
    text-align: center;
}

h1 {
    font-size: 36px;
}

p {
    width: 400px;
    margin-left: auto;
    margin-right: auto;
    text-align: center;
}
.center {
    height: 100vh;

    display: flex;
    align-items: center;
    justify-content: center;
}

td, th {
    text-align: center;      /* horizontal */
    vertical-align: middle;  /* vertical */
}