/* marquee div container */
.marquee {
    font-size: 2vw;
    color: #fff;
    font-family: 'Courier New', Courier, monospace;
    height: 2.5vw;
    overflow: hidden;
    background-color: transparent;
    position: relative;
    box-shadow: 0 5px 12px rgba(0, 0, 0, 0.5);
}
/* nested div inside the container */
.marquee div {
    display: block;
    width: 100%;
    position: absolute; 
    overflow: hidden;
    animation: marquee 12s linear infinite;
}
/* span with text */
.marquee span {
    float: left;
    width: 50%;
}


/* keyframe */
@keyframes marquee {
    0% { left: 0; }
    100% { left: -100%; }
}