nav.main-menu ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
}
nav.main-menu ul li {
    position: relative;
}
nav.main-menu ul li a {
    color: #fff;
    font-weight: bold;
    text-decoration: none;
    padding: 15px 20px;
    display: block;
}
/*nav.main-menu ul li:hover > a {
    background-color: #555;
}*/
nav.main-menu ul li ul {
    display: none;
    position: absolute;
    background-color: #555;
    min-width: 200px;
    z-index: 1000;
}
nav.main-menu ul li:hover ul {
    display: block;
}
nav.main-menu ul li ul li {
    width: 100%;
}
nav.main-menu ul li ul li a {
    padding: 10px 20px;
    color: #fff;
    background-color: #555;
}
nav.main-menu ul li ul li a:hover {
    background-color: #777;
}