html {
    height: 100%;
}

body, ul, li, p {
    margin: 0;
    padding: 0;
    font-size: 1.2rem;
    font-family: Arial, Helvetica, sans-serif;
}

header a {
    text-decoration: none;
    color: white;
}

h1 {
    font-size: 120%;
    text-align: center;
}

img {
    max-width: 100%;
    display: block;
}

header {
    background: #727272;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
}

.menu {
    display: flex;
}

.menu li {
    list-style: none;
    margin-left: 10px;
}


footer {
    background: #727272;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    color: white;
}


/* CSS FLEX BOX */ 

.flex {
    display: flex;
    max-width: 800px;
    margin: 0 auto;
    flex-wrap: wrap;
}

.flex > div {
    flex: 1 1 200px;
    margin: 10px;
}