html, body, #page { height: 100%; }
body > #page { height: auto; min-height: 100%; }

html {
    position: relative;
    min-height: 100%;
}
body {
    background-color: white;
    overflow: hidden;
} 
table {
        table-layout: fixed;
        border: 1px solid black;  
        border-spacing: 0;
        width: 50%;
        position: absolute;
        top: 50%;
        left: 50%;
        margin-right: -50%;
        transform: translate(-50%, -50%);
 }

td {
     border: 1px solid black; 
     font-size: 1vw;
     font-family: sans-serif;
     font-style: normal;
     font-weight: normal;
     width: 12.5vw;
     height: 12.5vw;
     text-align: center; 
     vertical-align: middle;
}

td a {
    display: block;
    line-height: 6.25vw;
    width: 100%;
    height: 100%;
}
/* unvisited link */
a:link {
    color: black;
    text-decoration: none;
}

/* visited link */
a:visited {
    color: black;
    text-decoration: none;
}

/* mouse over link */
 a:hover {
    color: black;
    text-decoration: none;
}

/* selected link */
a:active {
     color: black;
    text-decoration: none;
}

tr:nth-child(even) td:nth-child(even),
tr:nth-child(odd) td:nth-child(odd)
 {color: black; background: white;}

tr:nth-child(even) td:nth-child(odd),
tr:nth-child(odd) td:nth-child(even)
 {color: white; background: #73C2FB;} /* Maya blue */

footer {
    color: white;
    background-color: black;
    clear: both;
    position: relative;
    z-index: 10;
    height: 7.5vh;
    width: 100%;
    margin-top: -7.5vh;
}
button {
    background-color: #4CAF50; /* Green */
    border: none;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
}