html,
body,
.app {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}

.app {
    background: #999 url("img/hammy.png") no-repeat center center;
    background-size: cover;
    padding: 2rem;
}