*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.main-nav{
    margin-top: 10px;
    list-style: none;
    padding-left: 0;
    background-color: #13a4a4;
    display: flex;
    flex-wrap: wrap;
}

.main-nav-item{
    display: inline-block;
    border-right: 3px solid #ffff;
}

.main-nav-item a{
    color: white;
    padding: 5px;
    border-radius: 2px;
    text-decoration: none;
    background-color: red;
}

.main-nav-item a:hover{
    color: blue;
}

.main-nav-item a:active{
    color: white;
}

main{
    width: 100%;
    height: 500px;
    border: 10px solid gray;
    padding: 20px 35px;
}