style.css

body {
  background: #1b1d20;
}

img {
  max-width: 100%;
  display: block;
}

.slide {
  max-width: 380px;
  margin: 20px auto;

  display: grid;
  box-shadow: 0 4px 20px 2x rgba(0, 0, 0, 0.4);
}

.slide-items {
  position: relative;
  grid-area: 1/1;
  border-radius: 5px;
  overflow: hidden;
}

.slide-nav {
  grid-area: 1/1;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: auto 1fr;
}

.slide-nav button {
  -webkit-appearance: none;
  -webkit-tab-highlight-color: rgba(0, 0, 0, 0);
  opacity: 0;
}

.slide-items > * {
  opacity: 0;
  position: absolute;
  top: 0;
  pointer-events: none;
}

.slide-items > .active {
  opacity: 1;
  position: relative;
  pointer-events: initial;
}

.slide-thumb {
  display: flex;
  grid-column: 1 / 3;
}

.slide-thumb > span {
  flex: 1;
  display: block;
  height: 3px;
  background: rgba(0, 0, 0, 0.4);
  margin: 5px;
  border-radius: 3px;
  overflow: hidden;
}

.slide-thumb > span.active::after {
  content: '';
  display: block;
  height: inherit;
  background: rgba(255, 255, 255, 0.9);
  border-radius: 3px;
  transform: translateX(-100%);
  animation: thumb 3s forwards linear;
}

@keyframes thumb {
  to {
    transform: initial;
  }
}