*{
    padding: 0px;
    margin: 0px;
}

header{
    background-color: brown;
}

header>h1, header>h2{
    color:lime;
    text-align: center;
    font-family: Courier, monospace;
    padding: 0px 20px;
}
 
header > h1{
    font-size: 3rem;
}
 
header > h2{
    font-size: 2rem;
}
 
nav>ul{
    list-style-type: none;
    display: flex;
    flex-direction: column;
   
}
 
nav>ul>li{
    width: 100%;
}
 
nav>ul>li>a{
    background-color: lightgray;
    display: block;
    text-align: center;
    padding: 10px 0px;
    border: black solid 1px;
}
 
nav>ul>li>a:active{
    background-color: darkgray;
}
 
 
main{
    min-height: 500px;
    background-color: aquamarine;
}
 
main>article{
    margin: 10px 15px;
}
 
footer{
    background-color: lightcyan;
}
@media screen and (min-width: 600px) {
    header>h1, header>h2{
        background-color: blueviolet;
    }
    main{
        max-width: 700px;
        margin: auto;
    }
    nav>ul{
        flex-direction: row;           
        }
         
}
@media screen and (min-width: 900px) {
    body{
        max-width: 750px;
        margin: auto;
    }
    header>h1, header>h2{
        background-color: blue;
    }

    nav>ul{
        flex-direction: row;           
        }
         
    }