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

main {
  max-width: 800px;
  margin-inline: auto;
  --outline-color: red;
}

.container * {
  margin: 0;
  padding: 0;
}

.container {
  display: grid;
  position: relative;
  overflow: hidden;
  border-radius: 1rem;
  --position: 33%;
  outline: 5px solid var(--outline-color);
  outline-offset: 5px;
}

.slider-image {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: left;
}

.image-below {
  position: absolute;
  inset: 0;
  width: var(--position);
}

.slider {
  position: absolute;
  inset: 0;
  cursor: pointer;
  opacity: 0;
  /* for Firefox */
  width: 100%;
  height: 100%;
}

.slider:focus-visible ~ .slider-button {
  outline: 5px solid var(--outline-color);
  outline-offset: 3px;
}

.slider-line {
  position: absolute;
  inset: 0;
  width: 0.2rem;
  height: 100%;
  background-color: #fff;
  z-index: 10;
  left: var(--position);
  transform: translateX(-50%);
  pointer-events: none;
}

.slider-button {
  width: 48px;
  height: 48px;
  position: absolute;
  background-color: #fff;
  color: black;
  padding: 0.25rem;
  border-radius: 100vw;
  display: grid;
  place-items: center;
  top: 50%;
  left: var(--position);
  transform: translate(-50%, -50%);
  pointer-events: none;
  z-index: 100;
}