body { margin: 0; padding: 0; background-color: #000; }
.container { overflow: hidden; width: 100vw; height: 100vh; }
.slider { position: relative; }
.row::before, .row::after { content: ''; display: table; }
.row::after { clear: both; }
.panel { float: left; position: relative; }
.panel img { display: block; width: 80px; }
.panel img:last-child { position: absolute; left: 0; top: 0; opacity: 0; -webkit-transition: opacity 500ms 500ms; transition: opacity 500ms 500ms; }
.panel:hover img:last-child { opacity: 1; -webkit-transition-delay: 0s; transition-delay: 0s; -webkit-transition-duration: 0s; transition-duration: 0s; }