nav {
    position: fixed;
    top: 20px;
    left: 20px;
    border: 2px solid #333;
    border-radius: 21px;
    min-width: 40px;
    min-height: 40px;
    overflow: hidden;
}

nav input {
    display: none;
}

nav input:checked~label span:last-child {
    display: none;
}

nav input:not(:checked)~label span:first-child {
    display: none;
}

nav label {
    display: block;
    position: absolute;
    right: 0px;
    top: 0px;
    user-select: none;
    width: 41px;
    height: 41px;
    text-align: center;
    line-height: 40px;
    background: #333;
    color: white;
    border-bottom-left-radius: 20px;
    cursor: pointer;
}

nav ul {
    overflow: hidden;
    width: 0;
    height: 0;
    padding: 0;
    margin: 0;
    transition: width 0.5s, height 0.5s;
    list-style: none;
}

nav input:checked~ul {
    width: 200px;
    height: 90px;
}

nav ul li a {
    color: #333;
    text-transform: uppercase;
    text-decoration: none;
    font-family: 'Roboto', sans-serif;
    display: block;
    width: 200px;
    height: 30px;
    line-height: 30px;
    letter-spacing: 2px;
    text-align: center;
    transition: color 0.5s, background 0.5s;
}

nav ul li a:hover {
    background: #333;
    color: white;
}