* { box-sizing: border-box }

body { margin: 0 }

header, nav, article, footer {
    background-color: #5b9bd5;
    color: white;
    margin: 1vh 1vw;
}

header, footer {
    width: 96vw;
    text-align: center;
}

nav, article {
    float: left;
    height: 60vh;
}

header {
    height: 20vh;
    line-height: 20vh;
}

nav { width: 25vw }

article { width: 69vw }

footer {
    height: 10vh;
    line-height: 10vh;
}

@media (max-width: 690px) {
    nav, article {
        width: 96vw;
        height: auto;
    }
}

section:after {
    content: '';
    display: table;
    clear: both;
}

p, img { margin: 1em }

.box {
    border: 2px solid #cbcbcb;
    background-color: #538135;
    text-align: center;
    padding: 0.5em;
}

img {
    width: 10vw;
    height: 10vw;
    border: 2px solid #cbcbcb;
}

a { text-decoration: none }