html, body {
  margin: 0;
  width: 100%;
  background-color: #eff1f4;
}

header {
  position: sticky;
  left: 0;
  top: 0;
  width: 100%;
  line-height: 50px;
  text-align: center;
  background-color: #fff;
  font-weight: bold;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.container {
  display: flex;
}

.container .left-nav {
  width: 250px;
  height: auto;
  display: flex;
  justify-content: flex-end;
  padding-top: 30px;
  margin-right: 10px;
}

.container .left-nav .list {
  position: fixed;
  top: 50%;
  list-style: none;
  padding: 0;
  margin: 0;
  transform: translateY(-50%);
  border-left: 2px solid gray;
}

.container .left-nav .list .item {
  position: relative;
  margin: 15px 0;
  line-height: 3;
  color: gray;
  padding-left: 15px;
  cursor: pointer;
}

.container .left-nav .list .item:nth-child(1) {
  margin-top: 0;
}

.container .left-nav .list .item:last-child {
  margin-bottom: 0;
}

.container .left-nav .list .item.active {
  color: #d8152a;
}

.container .left-nav .list .item.active::after {
  content: '';
  position: absolute;
  top: 0;
  left: -2px;
  height: 100%;
  width: 2px;
  background-color: #d8152a;
}

.content-wraper {
  flex: 1;
}

.content-wraper section {
  width: calc(100% - 250px);
  height: 500px;
  margin: 15px 0;
  border-radius: 15px;
  background-color: #ddd;
  display: flex;
  justify-content: center;
  align-items: center;
}