index.css

*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: #000;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

/** 
 * the cool thing about Web components is that
 * we can provide a fully functional no-js fallback of the component
 */

image-slider {
  position: absolute;
  top: 0;
  left: 0;
  display: flex;
  width: 100vw;
  height: 100vh;
  justify-content: center;
  align-items: center;  
}

image-slider ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

image-slider ul li {
  margin: 0;
  padding: 0;
}

image-slider ul li img {
  display: block;
  width: 100vmin;
  height: 100vmin;
}


image-slider:not([index]) ul li:not(:first-child),
image-slider[index="1"] ul li:not(:nth-child(1)), 
image-slider[index="2"] ul li:not(:nth-child(2)),
image-slider[index="3"] ul li:not(:nth-child(3)),
image-slider[index="4"] ul li:not(:nth-child(4)),
image-slider[index="5"] ul li:not(:nth-child(5)),
image-slider[index="6"] ul li:not(:nth-child(6)),
image-slider[index="7"] ul li:not(:nth-child(7)),
image-slider[index="8"] ul li:not(:nth-child(8)),
image-slider[index="9"] ul li:not(:nth-child(9)) {
  display: none;
}


nav {
  position: absolute;
  bottom: 16px;
  left: 0;
  right: 0;
  display: block;
}

nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap-reverse;
  justify-content: center;
}

nav ul li {
  padding: 0;
  margin: 16px;
}

nav ul li a {
  font-variant-numeric: tabular-nums;
  display: block;
  padding: 8px;
  width: 40px;
  font-size: 16px;
  border: 2px solid #fff;
  background: #127;
  text-align: center;
  border-radius: 50%;
  color: #fff;
  text-decoration: none;
  font-weight: bold;
}

nav ul li a.active {
  background: #fff;
  color: #127;
  border: 2px solid #fff;
  
}