* { box-sizing: border-box;}
body {
    font-family: Arial, Helvetica, sans-serif;
}
#wrapper {
    width: 80%;
    margin-left: auto;
    margin-right: auto;
    border: thin solid black;
}
header {
    margin: 10px;
    padding: 10px;
    background-color: grey;
    color: white;
}
header > img {
    width:20%;
    height:auto;
    float:right;
}
.clearright {
    clear:right;
}
nav {
    display: flex;
    justify-content: center;
    text-align: center;
    flex: 1;
}
nav > div {
    background-color: #f1f1f1;
    margin: 10px;
    padding: 10px;
    font-size: 20px;
}
nav > div > a {
    color:steelblue;
    font-weight:bold;
    text-decoration:none;
}
nav > div> a:hover {
    color:red;
    text-decoration:underline;
}
main {
    display: flex;
}
main > div {
    background-color: #f1f1f1;
    margin: 10px;
    padding: 10px;
}
.left {
    flex: 2;
}
.left > img {
    width:40%;
    height:auto;
    float:right;
    margin:10px;
}
.right {
    flex: 1;
}
footer {
    background-color: gainsboro;
    margin: 10px;
    padding: 10px;
}
footer p {
    text-align: center;
}
@media only screen and (max-width: 1024px) {
    #wrapper {
        width: 100%;
        border: none;
    }
    header > img {
        width:25%;
        height:auto;
        float:right;
    }
}
@media only screen and (max-width: 510px) {

    nav {
        flex-direction: column;
    }   
    main {
        flex-direction: column;
    }   
    nav > div {
        width: auto;
        margin: 5px;
    }
    main > div {
        margin: 5px;
    }
    header > img {
        width:40%;
        height:auto;
        float:right;
    }
    .left > img {
        width:100%;
        height:auto;
        float:none;
        margin:0;
    }
}