* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    padding: 30px;
    font-family: "Helvetica Neue", helvetica, arial;
    background: url('https://subtlepatterns.com/patterns/white_carbonfiber.png');
}

#container {
    position: relative;
    width: 940px;
}

    #container:after {
        content: "";
        display: block;
        clear: both;
        height: 0;
    }

#menu {
    position: relative;
    float: left;
    width: 100%;
    padding: 0 20px;
    border-radius: 3px;
    box-shadow: inset 0 1px 1px rgba(255,255,255,.5), inset 0 -1px 0 rgba(0,0,0,.15), 0 1px 3px rgba(0,0,0,.15);
    background: #ccc;
}

    #menu, #menu ul {
        list-style: none;
    }

        #menu > li {
            float: left;
            position: relative;
            border-right: 1px solid rgba(0,0,0,.1);
            box-shadow: 1px 0 0 rgba(255,255,255,.25);
            perspective: 1000px;
        }

            #menu > li:first-child {
                border-left: 1px solid rgba(255,255,255,.25);
                box-shadow: -1px 0 0 rgba(0,0,0,.1), 1px 0 0 rgba(255,255,255,.25);
            }

        #menu a {
            display: block;
            position: relative;
            z-index: 10;
            padding: 13px 20px 13px 20px;
            text-decoration: none;
            color: rgba(75,75,75,1);
            line-height: 1;
            font-weight: 600;
            font-size: 12px;
            letter-spacing: -.05em;
            background: transparent;
            text-shadow: 0 1px 1px rgba(255,255,255,.9);
            transition: all .25s ease-in-out;
        }

        #menu > li:hover > a {
            background: #333;
            color: rgba(0,223,252,1);
            text-shadow: none;
        }

        #menu li ul {
            position: absolute;
            left: 0;
            z-index: 1;
            width: 200px;
            padding: 0;
            opacity: 0;
            visibility: hidden;
            border-bottom-left-radius: 4px;
            border-bottom-right-radius: 4px;
            background: transparent;
            overflow: hidden;
            transform-origin: 50% 0%;
        }


        #menu li:hover ul {
            padding: 15px 0;
            background: #333;
            opacity: 1;
            visibility: visible;
            box-shadow: 1px 1px 7px rgba(0,0,0,.5);
            animation-name: swingdown;
            animation-duration: 1s;
            animation-timing-function: ease;
        }

@keyframes swingdown {
    0% {
        opacity: .99999;
        transform: rotateX(90deg);
    }

    30% {
        transform: rotateX(-20deg) rotateY(5deg);
        animation-timing-function: ease-in-out;
    }

    65% {
        transform: rotateX(20deg) rotateY(-3deg);
        animation-timing-function: ease-in-out;
    }

    100% {
        transform: rotateX(0);
        animation-timing-function: ease-in-out;
    }
}

#menu li li a {
    padding-left: 15px;
    font-weight: 400;
    color: #ddd;
    text-shadow: none;
    border-top: dotted 1px transparent;
    border-bottom: dotted 1px transparent;
    transition: all .15s linear;
}

    #menu li li a:hover {
        color: rgba(0,223,252,1);
        border-top: dotted 1px rgba(255,255,255,.15);
        border-bottom: dotted 1px rgba(255,255,255,.15);
        background: rgba(0,223,252,.02);
    }