* {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

a { color: royalblue }

h1 { font-size: 36px }

h2 { font-size: 30px }

h3 { font-size: 24px }

h4 { font-size: 18px }

h5 { font-size: 14px }

h6 { font-size: 12px }

body {
    display: flex;
    flex-wrap: wrap;
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    font-size: 14px;
    line-height: 1.5;
    color: #333;
    background-color: #fff;
}

/* positioning */
#header,
#footer {
    padding: 8px 16px;
    width: 100%;
    background-color: rgba(0, 0, 0, .1);
}

#main { width: 75% }

#aside {
    padding: 0 8px;
    width: 25%;
    border-right: 1px solid #ccc;
}

#aside nav {
    /* reset */
    float: none;
    padding-left: 0;
    margin-top: 0;
    width: auto;
    border: 0;
}

#main pre { border: 2px solid rgba(0, 0, 0, .1) }
