style.css

/*
// .categories
*/
.categories {
  width: 255px;
  color: #fff;
  position: relative;
}

.categories__button {
  border: none;
  background: transparent;
  color: inherit;
  font-size: 15px;
  position: absolute;
  z-index: 1;
  width: 100%;
  top: 0;
  left: 0;
  height: 42px;
  line-height: 42px;
  cursor: default;
  font-weight: 500;
  padding: 0;
}

[dir=ltr] .categories__button {
  padding-right: 32px;
  padding-left: 47px;
  text-align: left;
}

[dir=rtl] .categories__button {
  padding-left: 32px;
  padding-right: 47px;
  text-align: right;
}

.categories__button:focus {
  outline: none;
}

.categories__button-icon {
  position: absolute;
  top: calc(50% - 7px);
  fill: #859ba6;
  -webkit-transition: fill .2s;
  transition: fill .2s;
}

[dir=ltr] .categories__button-icon {
  left: 16px;
}

[dir=rtl] .categories__button-icon {
  right: 16px;
}

.categories__button-arrow {
  position: absolute;
  top: calc(50% - 3px);
  fill: #859ba6;
  -webkit-transition: fill .2s, -webkit-transform .2s;
  transition: fill .2s, -webkit-transform .2s;
  transition: fill .2s, transform .2s;
  transition: fill .2s, transform .2s, -webkit-transform .2s;
}

[dir=ltr] .categories__button-arrow {
  right: 13px;
}

[dir=rtl] .categories__button-arrow {
  left: 13px;
}

.categories__body {
  max-width: 320px;
  position: relative;
  background: #3d464d;
  -webkit-box-shadow: none;
          box-shadow: none;
  border-radius: 2px;
  top: 0;
}

.categories__links {
  position: relative;
  list-style: none;
  padding: 0 0 14px;
  margin: 0;
  overflow-y: auto;
  overscroll-behavior-y: contain;
  -webkit-overflow-scrolling: touch;
  overflow-scrolling: touch;
}

.categories__item-link {
  font-weight: 400;
  position: relative;
  display: block;
  padding: 10px 16px;
  color: inherit;
  font-size: 14px;
  line-height: 16px;
  letter-spacing: .02em;
}

.categories__item-link:hover {
  color: inherit;
}

.categories__item--hover .categories__item-link {
  background: #525d66;
}

.categories__item-arrow {
  top: calc(50% - 5px);
  position: absolute;
  fill: #98aab3;
}

[dir=ltr] .categories__item-arrow {
  right: 14px;
  -webkit-transform: scaleX(1);
          transform: scaleX(1);
}

[dir=rtl] .categories__item-arrow {
  left: 14px;
  -webkit-transform: scaleX(-1);
          transform: scaleX(-1);
}

.categories__submenus-container {
  position: relative;
  height: calc(100% - 48px);
  padding-top: 48px;
  width: 100%;
}

.categories__submenu {
  position: relative;
  top: 0;
  visibility: hidden;
  display: none;
  z-index: 100;
}

[dir=ltr] .categories__submenu {
  left: 100%;
}

[dir=rtl] .categories__submenu {
  right: 100%;
}

.categories__submenu--type--megamenu {
  min-height: 100%;
  -webkit-box-flex: 1;
      -ms-flex-positive: 1;
          flex-grow: 1;
}

.categories__submenu--open {
  visibility: visible;
  opacity: 1;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
}

.categories__submenu--size--sm {
  width: 237px;
}

.categories__submenu--size--nl {
  width: 443px;
}

.categories__submenu--size--lg {
  width: 649px;
}

.categories__submenu--size--xl {
  width: 855px;
}

.categories__links-wrapper {
  overflow: hidden;
  height: 0;
  opacity: 0;
  -webkit-transition: height 0.25s ease-in-out, opacity 0.25s ease-in-out;
  transition: height 0.25s ease-in-out, opacity 0.25s ease-in-out;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
      -ms-flex-direction: column;
          flex-direction: column;
  max-height: 100%;
}

.categories__links-wrapper:before {
  display: block;
  content: '';
  height: 6px;
  -ms-flex-negative: 0;
      flex-shrink: 0;
}

.categories:not(.categories--fixed) .categories__button {
  cursor: pointer;
}

.categories:not(.categories--fixed) .categories__button:hover .categories__button-icon,
.categories:not(.categories--fixed) .categories__button:hover .categories__button-arrow {
  fill: currentColor;
}

.categories--open .categories__links-wrapper {
  overflow: visible;
  height: auto;
  opacity: 1;
}

.categories--open .categories__button-arrow {
  -webkit-transform: rotateZ(180deg);
          transform: rotateZ(180deg);
}

.categories--transition .categories__links,
.categories--transition .categories__links-wrapper {
  overflow: hidden;
}

@media (min-width: 992px) and (max-width: 1199px) {
  .categories {
    width: 210px;
  }
  .categories__submenu--size--sm {
    width: 204px;
  }
  .categories__submenu--size--nl {
    width: 376px;
  }
  .categories__submenu--size--lg {
    width: 548px;
  }
  .categories__submenu--size--xl {
    width: 720px;
  }
}