style.css

* {
  margin: 0;
  box-sizing: border-box;
}

body {
  font-family: "Roboto", sans-serif;
  background: #f7f6ff;
}

h2 {
  margin: 16px;
}

.container {
  margin-top: 100px;
  padding: 32px;
}

.select-box {
  position: relative;
  display: flex;
  width: 400px;
  flex-direction: column;
}

.select-box .options-container {
  background: #2f3640;
  color: #f5f6fa;
  max-height: 0;
  width: 100%;
  opacity: 0;
  transition: all 0.4s;
  border-radius: 8px;
  overflow: hidden;

  order: 1;
}

.selected {
  background: #2f3640;
  border-radius: 8px;
  margin-bottom: 8px;
  color: #f5f6fa;
  position: relative;

  order: 0;
}

.selected::after {
  content: "";
  background: url("img/arrow-down.svg");
  background-size: contain;
  background-repeat: no-repeat;

  position: absolute;
  height: 100%;
  width: 32px;
  right: 10px;
  top: 5px;

  transition: all 0.4s;
}

.select-box .options-container.active {
  max-height: 240px;
  opacity: 1;
  overflow-y: scroll;
  margin-top: 54px;
}

.select-box .options-container.active + .selected::after {
  transform: rotateX(180deg);
  top: -6px;
}

.select-box .options-container::-webkit-scrollbar {
  width: 8px;
  background: #0d141f;
  border-radius: 0 8px 8px 0;
}

.select-box .options-container::-webkit-scrollbar-thumb {
  background: #525861;
  border-radius: 0 8px 8px 0;
}

.select-box .option,
.selected {
  padding: 12px 24px;
  cursor: pointer;
}

.select-box .option:hover {
  background: #414b57;
}

.select-box label {
  cursor: pointer;
}

.select-box .option .radio {
  display: none;
}

/* Searchbox */

.search-box input {
  width: 100%;
  padding: 12px 16px;
  font-family: "Roboto", sans-serif;
  font-size: 16px;
  position: absolute;
  border-radius: 8px 8px 0 0;
  z-index: 100;
  border: 8px solid #2f3640;

  opacity: 0;
  pointer-events: none;
  transition: all 0.4s;
}

.search-box input:focus {
  outline: none;
}

.select-box .options-container.active ~ .search-box input {
  opacity: 1;
  pointer-events: auto;
}