menu {
    background-color: #81D4FA;
    list-style-type: none;
    margin: .25em;
    padding: .25em;
}

.outer {
    display: flex;
    flex-flow: row nowrap;
}

.outer>li {
    display: inline-block;
    margin: 0px .5em;
}

menu a {
    padding: .25em;
    text-decoration: none;
}

.inner {
    background-color: #81D4FA;
    display: none;
    position: absolute;
    z-index: 2;
}

.inner li {
    padding: .5em;
}

.inner li:hover {
    background-color: white;
    color: #01579B;
}

.outer li:hover .inner {
    display: block;
}