.popup_overlay
{
    background: -webkit-radial-gradient(rgba(255, 255, 255, 0), rgba(0, 0, 0, 0));
    background: -o-radial-gradient(rgba(255, 255, 255, 0), rgba(0, 0, 0, 0));
    background: -moz-radial-gradient(rgba(255, 255, 255, 0), rgba(0, 0, 0, 0));
    background: radial-gradient(rgba(255, 255, 255, 0), rgba(0, 0, 0, 0));
    z-index: 1000;
    position: fixed;
    width: 100vw;
    height: 100vh;
    top: 0;
    left: 0;
    visibility: hidden;
    opacity: 0;
    transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    -webkit-transition: all 0.3s ease-in-out;
}
.popup_overlay.show
{
    background: -webkit-radial-gradient(rgba(255, 255, 255, 0.5), rgba(0, 0, 0, 0.5));
    background: -o-radial-gradient(rgba(255, 255, 255, 0.5), rgba(0, 0, 0, 0.5));
    background: -moz-radial-gradient(rgba(255, 255, 255, 0.5), rgba(0, 0, 0, 0.5));
    background: radial-gradient(rgba(255, 255, 255, 0.5), rgba(0, 0, 0, 0.5));
    visibility: visible;
    opacity: 1;
    transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    -webkit-transition: all 0.3s ease-in-out;
}

.popup
{
    display: inline-block;
    position: relative;
    margin-top: 2em;
    padding: 1em;
    background-color: #F0F0F0;
    color: #808080;
    text-align: center;
    box-shadow: 2px 2px 5px rgba(0, 0, 0, 0.5);
    z-index: 1010;
}
.popup_button
{
    position: absolute;
    height: 1.5em;
    padding: 1em;
    border-radius: 50%;
    background-color: rgba(0, 0, 0, 0.5);
    cursor: pointer;
    z-index: 1020;
}
.popup_button.close
{
    right: -1.5em;
    top: -1.5em;
}