html, body {
    height: 100%;
    margin: 0;
}
body {
    color: #f8f9fa;
    background-color: #212529;
    background: radial-gradient(circle at center top, #212529 0%, #060707 100%);
    background-repeat: no-repeat;
    background-attachment: fixed;
    display: flex;
    flex-flow: column;
}
/*html > body > * {
    background: none;
}*/
header {
    background-color: rgba(0,0,0,0.1);
    border-bottom: 2px solid #e9ecef;
    margin-bottom: 32px;
}
section {
    margin-bottom: 30px;
}
main {
    width: 100%;
}
.main-row {
    width: 100%;
    flex-grow: 1;
    flex-shrink: 1;
    flex-basis: auto;
}
footer {
    text-align: center;
    flex-grow: 0;
    flex-shrink: 1;
    flex-basis: auto;
    padding-top: 20px;
    padding-bottom: 30px;
    background-color: #495057;
}
h1 {
    padding-top: 12px;
    text-align: center;
    color: #f8f9fa;
}
h3 {
    text-align: center;
    color: #6c757d;
}
.ad {
    background-color: grey;
}