LeaVerou/awesomplete

.awesomplete > ul {
    border-radius: .3em;
    margin: .2em 0 0;
    background: hsla(0,0%,100%,.9);
    background: linear-gradient(to bottom right, white, hsla(0,0%,100%,.8));
    border: 1px solid rgba(0,0,0,.3);
    box-shadow: .05em .2em .6em rgba(0,0,0,.2);
    text-shadow: none;
}

@supports (transform: scale(0)) {
    .awesomplete > ul {
        transition: .3s cubic-bezier(.4,.2,.5,1.4);
        transform-origin: 1.43em -.43em;
    }
    
    .awesomplete > ul[hidden],
    .awesomplete > ul:empty {
        opacity: 0;
        transform: scale(0);
        display: block;
        transition-timing-function: ease;
    }
}

    /* Pointer */
    .awesomplete > ul:before {
        content: "";
        position: absolute;
        top: -.43em;
        left: 1em;
        width: 0; height: 0;
        padding: .4em;
        background: white;
        border: inherit;
        border-right: 0;
        border-bottom: 0;
        -webkit-transform: rotate(45deg);
        transform: rotate(45deg);
    }

    .awesomplete > ul > li {
        position: relative;
        padding: .2em .5em;
        cursor: pointer;
    }
    
    .awesomplete > ul > li:hover {
        background: hsl(200, 40%, 80%);
        color: black;
    }
    
    .awesomplete > ul > li[aria-selected="true"] {
        background: hsl(205, 40%, 40%);
        color: white;
    }
    
        .awesomplete mark {
            background: hsl(65, 100%, 50%);
        }
        
        .awesomplete li:hover mark {
            background: hsl(68, 100%, 41%);
        }
        
        .awesomplete li[aria-selected="true"] mark {
            background: hsl(86, 100%, 21%);
            color: inherit;
        }