Carousel slider

Lien d’origine: https://codepen.io/Schepp/pen/WNbQByE

HTML:

<div class="block carouselblock">
<center><section class="carousel" aria-label="Gallery">
<ol class="carousel__viewport">
<li id="carousel__slide1"
tabindex="0"
class="carousel__slide">
<div class="carousel__snapper">
<a href="#carousel__slide4"
class="carousel__prev">Go to last slide</a>
<a href="#carousel__slide2"
class="carousel__next">Go to next slide</a>
</div>
</li>
<li id="carousel__slide2"
tabindex="0"
class="carousel__slide">
<div class="carousel__snapper"></div>
<a href="#carousel__slide1"
class="carousel__prev">Go to previous slide</a>
<a href="#carousel__slide3"
class="carousel__next">Go to next slide</a>
</li>
<li id="carousel__slide3"
tabindex="0"
class="carousel__slide">
<div class="carousel__snapper"></div>
<a href="#carousel__slide2"
class="carousel__prev">Go to previous slide</a>
<a href="#carousel__slide4"
class="carousel__next">Go to next slide</a>
</li>
<li id="carousel__slide4"
tabindex="0"
class="carousel__slide">
<div class="carousel__snapper"></div>
<a href="#carousel__slide3"
class="carousel__prev">Go to previous slide</a>
<a href="#carousel__slide1"
class="carousel__next">Go to first slide</a>
</li>
</ol>
<aside class="carousel__navigation">
<ol class="carousel__navigation-list">
<li class="carousel__navigation-item">
<a href="#carousel__slide1"
class="carousel__navigation-button">Go to slide 1</a>
</li>
<li class="carousel__navigation-item">
<a href="#carousel__slide2"
class="carousel__navigation-button">Go to slide 2</a>
</li>
<li class="carousel__navigation-item">
<a href="#carousel__slide3"
class="carousel__navigation-button">Go to slide 3</a>
</li>
<li class="carousel__navigation-item">
<a href="#carousel__slide4"
class="carousel__navigation-button">Go to slide 4</a>
</li>
</ol>
</aside>
</section></center>
</div>

CSS:

@keyframes tonext {
75% {
left: 0;
}
95% {
left: 100%;
}
98% {
left: 100%;
}
99% {
left: 0;
}
}
@keyframes tostart {
75% {
left: 0;
}
95% {
left: -300%;
}
98% {
left: -300%;
}
99% {
left: 0;
}
}
@keyframes snap {
96% {
scroll-snap-align: center;
}
97% {
scroll-snap-align: none;
}
99% {
scroll-snap-align: none;
}
100% {
scroll-snap-align: center;
}
}
.carouselblock {
max-width: 37.5rem;
margin: 0 auto;
padding: 0 1.25rem;
font-family: 'Lato', sans-serif;
}
.carouselblock .carousel {
box-sizing: border-box;
scrollbar-color: transparent transparent;
scrollbar-width: 0px;
} 
.carouselblock .carousel ::-webkit-scrollbar {
width: 0;
}
.carouselblock .carousel ::-webkit-scrollbar-track {
background: transparent;
}
.carouselblock .carousel ::-webkit-scrollbar-thumb {
background: transparent;
border: none;
}
.carouselblock .carousel {
-ms-overflow-style: none;
}
.carouselblock .carousel ol, .carouselblock .carousel li {
list-style: none;
margin: 0;
padding: 0;
}
.carouselblock .carousel {
position: relative;
padding-top: 75%;
filter: drop-shadow(0 0 10px #0003);
perspective: 100px;
}
.carouselblock .carousel .carousel__viewport {
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
display: flex;
overflow-x: scroll;
counter-reset: item;
scroll-behavior: smooth;
scroll-snap-type: x mandatory;
}
.carouselblock .carousel .carousel__slide {
position: relative;
flex: 0 0 100%;
width: 100%;
background-color: #f99;
counter-increment: item;
}
.carouselblock .carousel .carousel__slide:nth-child(even) {
background-color: #99f;
}
.carouselblock .carousel .carousel__slide:before {
content: counter(item);
position: absolute;
top: 50%;
left: 50%;
transform: translate3d(-50%,-40%,70px);
color: #fff;
font-size: 2em;
}
.carouselblock .carousel .carousel__snapper {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
scroll-snap-align: center;
}
@media (hover: hover) {
.carouselblock .carousel .carousel__snapper {
animation-name: tonext, snap;
animation-timing-function: ease;
animation-duration: 4s;
animation-iteration-count: infinite;
}
.carouselblock .carousel .carousel__slide:last-child .carousel__snapper {
animation-name: tostart, snap;
}
}
@media (prefers-reduced-motion: reduce) {
.carouselblock .carousel .carousel__snapper {
animation-name: none;
}
}
.carouselblock .carousel:hover .carousel__snapper,
.carouselblock .carousel:focus-within .carousel__snapper {
animation-name: none;
}
.carouselblock .carousel .carousel__navigation {
position: absolute;
right: 0;
bottom: 0;
left: 0;
text-align: center;
}
.carouselblock .carousel .carousel__navigation-list,
.carouselblock .carousel .carousel__navigation-item {
display: inline-block;
}
.carouselblock .carousel .carousel__navigation-button {
display: inline-block;
width: 1.5rem;
height: 1.5rem;
background-color: #333;
background-clip: content-box;
border: 0.25rem solid transparent;
border-radius: 50%;
font-size: 0;
transition: transform 0.1s;
}
.carouselblock .carousel::before,
.carouselblock .carousel::after,
.carouselblock .carousel .carousel__prev,
.carouselblock .carousel .carousel__next {
position: absolute;
top: 0;
margin-top: 37.5%;
width: 4rem;
height: 4rem;
transform: translateY(-50%);
border-radius: 50%;
font-size: 0;
outline: 0;
}
.carouselblock .carousel::before,
.carouselblock .carousel .carousel__prev {
left: -1rem;
}
.carouselblock .carousel::after,
.carouselblock .carousel .carousel__next {
right: -1rem;
}
.carouselblock .carousel::before,
.carouselblock .carousel::after {
content: '';
z-index: 1;
background-color: #333;
background-size: 1.5rem 1.5rem;
background-repeat: no-repeat;
background-position: center center;
color: #fff;
font-size: 2.5rem;
line-height: 4rem;
text-align: center;
pointer-events: none;
}
.carouselblock .carousel::before {
background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'%3E%3Cpolygon points='0,50 80,100 80,0' fill='%23fff'/%3E%3C/svg%3E");
}
.carouselblock .carousel::after {
background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'%3E%3Cpolygon points='100,50 20,100 20,0' fill='%23fff'/%3E%3C/svg%3E");
}