html,
body {
    height: 100%;
    margin: 0;
}
body{
    background-color: #CCC;
    background: url(bg.png);
    background-repeat: no-repeat;
    background-size: 100% 100%;
}

.container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.logo {
    max-width: 100%;
    height: auto;
}