style.css

* {
    box-sizing: border-box;
}

html {
    height:100%;
    margin:0;
    padding: 0;
}
body {
    color:#555;
    margin:0;
    text-align: center;
    font-family:-apple-system, BlinkMacSystemFont, 'SF UI Text', 'Helvetica Neue', 'Roboto', 'Arial Nova', 'Segoe UI', 'Arial', sans-serif;
    min-height:100%;
    display:flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

h1 {
    color:#222;
    font-weight: 300;
    font-size: 4em;
}

img.logo {
    width:8em;
}

nav.main a {
    display:inline-block;
    padding:0 1em;
    color:#d04;
    text-decoration: none;
}

nav.main a:hover {
    text-decoration: underline;
}

header {
    padding: 3em;
}

.content {
    flex:1;
    display:flex;
    flex-wrap:wrap;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    background-color:#eee;
    width:100%;
    padding:3em;
}