material_dropdown.css

/* https://codepen.io/mildrenben/pen/RPwQEY */

@media only screen and (max-width:44.9375em) {
    .drop {
        display: none;
    }
}

.drop {
    width: 5.3rem;
    vertical-align: middle;
}

@media only screen and (min-width:60em) and (max-width:70em) {
    .drop {
        width: 4.7rem;
    }
    /* also narrow nav source width */
    .md-header-nav__source {
        width: 10rem;
    }
}

.drop button {
    color: inherit;
    font-weight: 700;
    font-size: .65rem;
    cursor: pointer;
}

.drop button:after {
    content: "\e5c5";
    padding: 0 0 0.3rem 0.2rem;
    font-size: 0.5rem;
    font-family: "Material Icons";
    display: inline-block;
    transition: all 0.2s ease;
    transform: rotate(0);
    transform-origin: 65% 30%;
}

.drop button.active:after {
    transform: rotate(180deg);
}

.drop ul {
    position: absolute;
    left: 0;
    top: 6em;
    transition: all 0.1s ease;
    padding: .625em 0;
    margin-top: -0.9rem;
    transform: scale(0);
    transform-origin: 0 0;
    background: #fcfcfc;
    box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.16), 0 2px 8px 0 rgba(0, 0, 0, 0.12);
}

.drop ul.active {
    transform: scale(1);
}

.drop ul li {
    display: block;
    width: 100%;
}

.drop ul li a.md-nav__link {
    width: 100%;
    padding: .4rem 1em;
    display: inline-block;
    white-space: pre;
    box-sizing: border-box;
    color: rgba(0, 0, 0, .87);
    margin-top: 0;
    font-size: .75rem;
}