.dropdown-toggle {
    border: none;
    background-color: transparent;
    outline: 0;
}

.dropdown-toggle:focus {
    box-shadow: none;
    border: none;
    outline: 0;
}

.dropdown-toggle[aria-expanded="true"]:after {
    transform: rotate(180deg);
}

.dropdown-toggle:after {
    transition: 0.1s;
}