style.css

@import url("https://fonts.googleapis.com/css2?family=Roboto&display=swap");

* {
  box-sizing: border-box;
}

body {
  font-family: "Roboto", sans-serif;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100vh;
  overflow: hidden;
  margin: 0;
  background-position: center center;
  background-size: cover;
  transition: 0.5s ease;
}

body::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
  background-color: rgba(0, 0, 0, 0.7);
  z-index: -1;
}

.slide-container {
  box-shadow: 0 3px 6px rgba(0, 0, 0, 0.16), 0 3px 6px rgba(0, 0, 0, 0.23);
  height: 70vh;
  width: 70vw;
  position: relative;
  overflow: hidden;
}

.slide {
  opacity: 0;
  height: 100vh;
  width: 100vw;
  background-position: center center;
  background-size: cover;
  position: absolute;
  top: -15vh;
  left: -15vw;
  transition: 0.5s ease;
  z-index: 1;
}

.slide.active {
  opacity: 1;
}

.arrow {
  position: fixed;
  cursor: pointer;
  background-color: transparent;
  color: rgba(255, 255, 255, 0.75);
  padding: 20px;
  font-size: 30px;
  border: 2px solid orange;
  top: 50%;
  transform: translateY(-50%);
}

button:focus {
  outline: none;
}

.arrow.arrow-left {
  left: calc(15vw - 65px);
}

.arrow.arrow-right {
  right: calc(15vw - 65px);
}

@media screen and (max-width: 768px) {
  .slide {
    background-image: url("https://source.unsplash.com/random/720x1024?mountain");
  }
  body {
    background-image: url("https://source.unsplash.com/random/720x1024?mountain");
  }
}

@media screen and (max-width: 425px) {
  .arrow.arrow-left {
    left: 50%;
    transform: translateX(-50%) rotate(90deg);
    top: calc(15vh - 78px);
  }
  .arrow.arrow-right {
    right: 50%;
    top: calc(85vh);
    bottom: calc(15vh - 78px);
    transform: translateX(50%) rotate(90deg);
  }
}