body {
    margin: 0;
    padding: 0;
}

header {
    width: 100%;
    background: #555;
    color: white;
    font-size: 3em;
    text-align: center;
}

.container {
    display: flex;
    justify-content: center;
}

menu {
    width: 200px;
    float: left;
    background: grey;
    margin: 0;
    padding: 0;
    order: 1;
}

menu ul {
    margin: 0;
    padding: 0;
}

menu ul li {
    margin: 0;
    padding: 0;
    list-style-type: none;
}

menu ul li a {
    text-decoration: none;
    color: white;
    font-weight: bold;
    display: block;
    border-bottom: 1px red;
    padding: 5px 15px;
}

main {
    width: 570px;
    padding: 0 15px;
    order: 2;
}

footer {
    background: #555;
    color: white;
    width: 100%;
    text-align: center;
}