/* --- start --- this style is constant ---------- */
@keyframes slider-key-next {
  0% {left: 100%; }
  100% {left: 0; }
}
@keyframes slider-key-left {
  0% {left: 0; }
  100% {left: -100%; }
}
@keyframes slider-key-previous {
  0% {left: -100%; }
  100% {left: 0; }
}
@keyframes slider-key-right {
  0% {left: 0; }
  100% {left: 100%; }
}
.slider {
  position: relative;
}
.slider > ul {
  margin: 0;
  padding: 0;
  list-style: none;
  position: relative;
  float: left;
  width: 100%;
  overflow: hidden;
}
.slider > ul > li {
  position: absolute;
  left: 100%;
  top: 0;
  width: 100%;
  height: 100%;
  visibility: hidden;
  animation-timing-function: ease-in-out;
  animation-fill-mode: forwards;
}
.slider > ul > li.active {visibility: visible; left: 0; }
.slider > ul > li.left {animation-name: slider-key-left; }
.slider > ul > li.next {animation-name: slider-key-next; }
.slider > ul > li.right {animation-name: slider-key-right; }
.slider > ul > li.previous {animation-name: slider-key-previous; }
/* --- end --- this style is constant ---------- */


/* -- your style here -- */
.slider > button {
  transition: 0.3s;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 40px;
  height: 40px;
  background-color: #FAFAFA;
  opacity: 0.5;
  border: 0;
  outline: none;
  padding: 0;
  cursor: pointer;
  border-radius: 100%;
  box-shadow: 0 3px 6px rgba(0,0,0,0.2);
  background-size: 60%;
  background-repeat: no-repeat;
  background-position: center;
}
.slider > button:hover {
  opacity: 1;
  box-shadow: 0 5px 10px rgba(0,0,0,0.2);
}

.slider > ul > li > img {
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
}
.slider > ul > li {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 0;
}