CSS for embedded hover footnotes in Ghost 1.0 default theme

embedded-hover-footnotes.css

/* Thanks to w3schools for the base sample implementation of tooltips with CSS only:
      https://www.w3schools.com/howto/howto_css_tooltip.asp */
.tooltip {
    position: relative;
}
.tooltip .tooltiptext {
    visibility: hidden;
    width: 240px;
    background-color: #555;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px 0;
    position: absolute;
    z-index: 1;
    bottom: 90%;
    left: 50%;
    margin-left: -120px;
    opacity: 0;
    transition: opacity .5s;
    line-height: 1.1em;
    font-size: 90%;
    padding: .5em;
}
.tooltip .tooltiptext * {
    color: #fff;
}
    
.tooltip .tooltiptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #555 transparent transparent transparent;
}
.tooltip:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
}
    
.tooltip a.footnote-backref {
    display: none;
}