/* 基础样式 */
* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  font-family: "华文楷体", "STKaiti", "KaiTi", "楷体", serif;
}

/* 容器与背景 */
.shell {
  width: 100%;
  position: relative;
  padding: 80px 0;
  transition: 0.3s ease 0s;
  background-attachment: fixed;
  background-size: cover;
}
.shell::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(99,99,99, 0.8);
}

/* 头部 */
header {
  width: 100%;
  text-align: center;
  margin-bottom: 80px;
  position: relative;
}
.title {
  font-size: 46px;
  color: #fff;
  font-weight: normal;
  margin: 10px 0 0 0;
}
.subtitle {
  color: rgba(255, 255, 255, 0.5);
  font-size: 16px;
  letter-spacing: 5px;
  margin: 10px 0 0 0;
  font-weight: normal;
}

/* 时间线 */
.timeline {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  max-width: 700px;
  margin: 0 auto;
  position: relative;
}
.timeline::before {
  position: absolute;
  left: 50%;
  width: 2px;
  height: 100%;
  margin-left: -1px;
  content: '';
  background-color: rgba(255, 255, 255, 0.07);
}

/* 时间线条目 */
.item {
  width: calc(50% - 40px);
  display: flex;
  position: relative;
  padding: 50px 0;
  opacity: 1;
  filter: none;
  transition: 0.5s;
  transform: none;
}
.item:nth-child(even) {
  align-self: flex-end;
}
.item::before {
  content: attr(data-text);
  position: absolute;
  top: 70%;
  right: calc(-100% - 56px);
  width: 100%;
  color: rgba(255, 255, 255, 0.5);
  font-size: 13px;
  border-left: 2px solid rgba(255, 255, 255, 0.5);
  margin-top: -5px;
  padding-left: 15px;
  opacity: 0;
  font: 900 20px '';
  letter-spacing: 5px;
}
.item:nth-child(even)::before {
  right: auto;
  left: calc(-100% - 56px);
  text-align: right;
  padding-left: 0;
  border-left: none;
  border-right: 2px solid rgba(255, 255, 255, 0.5);
  padding-right: 15px;
}

/* 激活状态 */
.item--active {
  opacity: 1;
  filter: blur(0px);
  transform: translateY(0);
}
.item--active::before {
  opacity: 1;
  transition: 0.3s all 0.2s;
  top: 50%;
}
.item--active .content-title {
  margin: -50px 0 20px 0;
}

/* 内容 */
.content-title {
  font-size: 66px;
  color: #fff;
  font-weight: normal;
  margin: -10px 0 0 0;
  transition: 0.4s;
  padding: 0 10px;
}
.content-desc {
  margin: 0;
  font-size: 15px;
  color: rgba(255, 255, 255, 0.7);
  line-height: 25px;
}
.img {
  max-width: 100%;
  box-shadow: 0 10px 15px rgba(0, 0, 0, 0.4);
}

/* footer */
.footer {
  padding: 95px 0;
  text-align: center;
}
.footer a {
  color: #999;
  display: inline-block;
}

/* 显隐动画与状态 */
.hide-body .timeline,
.hide-body header {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.5s;
}
.show-body .timeline,
.show-body header {
  opacity: 1;
  pointer-events: auto;
  transition: opacity 0.5s;
}

/* 滚动后（show-body）才有透明、模糊、上移 */
.show-body .item {
  opacity: 0.3;
  filter: blur(2px);
  transform: translateY(-80px);
}
.show-body .item--active {
  opacity: 1;
  filter: blur(0px);
  transform: translateY(0);
}
.hide-body .item {
  opacity: 1 !important;
  filter: none !important;
  transform: none !important;
}
.hide-body .shell::before,
.hide-body .timeline::before {
  background-color: transparent !important;
}

/* 动画 */
@keyframes fadeInFromCenter {
  0% {
    opacity: 0;
    transform: scaleX(0.5);
  }
  100% {
    opacity: 1;
    transform: scaleX(1);
  }
}
.show-body .timeline {
  animation: fadeInFromCenter 0.6s cubic-bezier(.4,0,.2,1);
}

/* 响应式 */
@media only screen and (max-width: 767px) {
  .item {
    align-self: baseline !important;
    width: 100%;
    padding: 0 30px 150px 80px;
  }
  .item:before {
    left: 10px !important;
    padding: 0 !important;
    top: 50px;
    text-align: center !important;
    width: 60px;
    border: none !important;
  }
  .item:last-child {
    padding-bottom: 40px;
  }
  .timeline:before {
    left: 40px;
  }
}