body {
  display: flex;
  min-height: 100vh;
  background-color: #e6e6fa;
}
#c-slider {
  margin: auto;
  width: 90%;
  max-width: 900px;
  position: relative;
  overflow: hidden;
  box-shadow: 0 0 0 10px #fff, 0 15px 50px;
}

#slider {
  display: flex;
  width: 500%;
}

section {
  width: 100%;
}

#slider img {
  display: block;
  width: 100%;
  height: 100%;
}
#btn-prev,
#btn-next {
  width: 40px;
  height: 40px;
  background: rgba(255, 255, 255, 0.7);
  position: absolute;
  top: 63%;
  transform: translateY(-50%);
  line-height: 40px;
  font-size: 25px;
  font-weight: bold;
  text-align: center;
  border-radius: 50%;
  font-family: monospace;
  cursor: pointer;
}
#btn-prev:hover,
#btn-next:hover {
  background: rgba(255, 255, 255, 1);
}
#btn-prev {
  left: 10px;
}
#btn-next {
  right: 10px;
}