*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
header{
background-color: blue;
padding: 3em;
color: #fff;
text-align: center;
}
section>nav{
    float: left;
    width: 30%;
    background-color: burlywood;
    padding: 1.5em;
    height: 250px;
}
section>nav>ul{
    list-style: none;
}
section>nav>li>a{
    text-decoration: none;
    color: #000

}

article{
    float: left;
    padding: 20px;
    width: 70px;
    /*background-color: aqua; */
}
footer{
    background-color: #ccc;
    padding: 20px;
    text-align: center;
}

.clearfix::after{
    content: '';
    display: block;
    clear: both;
    overflow: hidden;
}

/*반응형웹 */
@media screen and (max-width:600px;) {
    nav, article{
        width: 100%;
        height: auto;
    }
}