a {
    color: #FFFFFF;
    text-decoration: none;
}

body {
    background-image: linear-gradient(to top right, #080B14, #31333F);
    background-repeat: no-repeat;
    background-attachment: fixed;
    margin: auto;
    border: 0px;
    padding-top: 125px;
    text-align: center;
    color: #FFFFFF;
    font-family: Helvetica, Arial;
    font-size: 18px;
}

img {
    vertical-align: middle;
}

@media screen and (max-width:600px){
    table {
        border-collapse:separate;
        border:solid #31333F 1px;
        border-radius:15px;
        background-color: #31333F;
        text-align: center;
        align-self: center;
        width: 75%;
        margin: auto;
        padding: 5px;
        vertical-align: middle;
    }
}

@media screen and (min-width:601px){
    table {
        border-collapse:separate;
        border:solid #31333F 1px;
        border-radius:15px;
        background-color: #31333F;
        text-align: center;
        align-self: center;
        width: 35%;
        margin: auto;
        padding: 5px;
        vertical-align: middle;
    }
}

td, th {
    border-left:solid white 0px;
    border-top:solid white 0px;
    width: 100%;
    vertical-align: middle;
}

th {
    background-color: blue;
    border-top: none;
}

td:first-child, th:first-child {
     border-left: none;
}