@keyframes itemactive {
  0% {
    opacity: 0;
    transform: translateY(-20%);
  }
  10% {
    opacity: 1;
    transform: translateY(0%);
  }
  90% {
    opacity: 1;
    transform: translateY(0%);
  }
  100% {
    opacity: 0;
    transform: translateY(20%);
  }
}
@keyframes bgactive {
  0% {
    transform: scale(1);
  }
  100% {
    transform: scale(1.1);
  }
}
@keyframes fadeout {
  0% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}
@keyframes show {
  0% {
    opacity: 0;
    transform: translateY(-30px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}
@keyframes text {
  0% {
    opacity: 0;
    transform: translateY(30px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}
@keyframes scale {
  0% {
    transform: scale(0.95);
    opacity: 0;
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}
body {
  background-color: #202124;
}
section.main {
  animation: show 0.3s linear forwards;
  width: 100%;
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  background: skyblue;
}
section.main .bg {
  position: absolute;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1;
}
section.main .bg .bg-item {
  position: absolute;
  width: 100%;
  height: 100%;
  overflow: hidden;
  z-index: 1;
}
section.main .bg .bg-item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  display: none;
  transform: scale(1.1);
}
section.main .bg .bg-item:nth-of-type(even) img {
  transform: scale(1);
}
section.main .bg .bg-item.active {
  z-index: 2;
}
section.main .bg .bg-item.active img {
  display: block;
  animation: bgactive 5s ease-in-out forwards;
}
section.main .bg .bg-item.active:nth-of-type(2n) img {
  display: block;
  animation: bgactive 5s ease-in-out reverse forwards;
}
section.main .bg .bg-item.previous {
  z-index: 3;
}
section.main .bg .bg-item.previous img {
  display: block;
  animation: fadeout 1s ease-out forwards;
}
section.main .content {
  padding: 100px;
  position: relative;
  z-index: 10;
  display: flex;
  flex-direction: column;
}
section.main .content .title {
  font-size: 96px;
  color: #fff;
  opacity: 0;
  animation: show 0.5s linear forwards;
}
section.main .content .options {
  margin: 40px 0;
  opacity: 0;
  animation: show 0.5s linear forwards;
  animation-delay: 0.5s;
}
section.main .content .options .item {
  display: none;
  opacity: 0;
  color: white;
  font-size: 22px;
}
section.main .content .options .item.active {
  display: block;
  animation: itemactive 5s linear;
}
section.main .content #download_button {
  border: 2px solid #fff;
  width: 150px;
  text-align: center;
  height: 40px;
  line-height: 40px;
  color: #fff;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  opacity: 0;
  animation: show 0.5s linear forwards;
  animation-delay: 0.7s;
}
section.main .content #download_button span {
  position: relative;
  z-index: 2;
  transition: all 0.3s ease-in-out;
}
section.main .content #download_button::after {
  content: '';
  position: absolute;
  top: -100%;
  left: 0;
  width: 100%;
  height: 100%;
  background: #FFF;
  transition: all 0.3s ease-in-out;
}
section.main .content #download_button:hover::after {
  top: 0;
}
section.main .content #download_button:hover span {
  color: #1A73E8;
}
section.introduce {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  color: white;
  padding-top: 120px;
}
section.introduce .card .title {
  font-weight: 400;
  text-align: center;
  font-size: 34px;
  opacity: 0;
}
section.introduce .card .title.show {
  animation: text 0.5s linear forwards;
}
section.introduce .card .des {
  width: 35vw;
  min-width: 570px;
  font-weight: 400;
  font-size: 16px;
  text-align: center;
  line-height: 23px;
  margin: 0 auto;
  margin-top: 15px;
  opacity: 0;
}
section.introduce .card .des.show {
  animation: text 0.5s linear forwards;
  animation-delay: 0.5s;
}
section.introduce .info_1 > img {
  margin-top: 25px;
  min-width: 570px;
  width: 40vw;
  opacity: 0;
}
section.introduce .info_1 > img.show {
  animation: scale 0.5s linear forwards;
  animation-delay: 1s;
}
section.introduce .info_2 {
  margin-top: 150px;
}
section.introduce .info_2 .title {
  margin-bottom: 25px;
}
section.introduce .info_2 .list {
  margin-top: 50px;
  width: 50vw;
  min-width: 570px;
  display: grid;
  grid-template-columns: 1fr repeat(3, 1fr);
  grid-gap: 10px;
}
section.introduce .info_2 .list.show .item {
  animation: scale 0.5s linear forwards;
}
section.introduce .info_2 .list.show .item:nth-of-type(1) {
  animation-delay: 0.8s;
}
section.introduce .info_2 .list.show .item:nth-of-type(2) {
  animation-delay: 1s;
}
section.introduce .info_2 .list.show .item:nth-of-type(3) {
  animation-delay: 1.2s;
}
section.introduce .info_2 .list.show .item:nth-of-type(4) {
  animation-delay: 1.4s;
}
section.introduce .info_2 .list.show .item:nth-of-type(5) {
  animation-delay: 1.6s;
}
section.introduce .info_2 .list .item {
  position: relative;
  opacity: 0;
  overflow: hidden;
  cursor: pointer;
}
section.introduce .info_2 .list .item:hover::after {
  opacity: 1;
}
section.introduce .info_2 .list .item:hover .mask {
  opacity: 1;
  transform: translateY(0);
}
section.introduce .info_2 .list .item::after {
  opacity: 0;
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transition: all 0.3s ease-in-out;
  background-image: radial-gradient(circle, rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0.5) 100%);
}
section.introduce .info_2 .list .item img {
  width: 100%;
  height: 100%;
}
section.introduce .info_2 .list .item .mask {
  position: absolute;
  bottom: 0;
  padding: 24px;
  z-index: 2;
  transform: translateY(30%);
  transition: all 0.3s ease-in-out;
  opacity: 0;
}
section.introduce .info_2 .list .item .mask .item_title {
  font-size: 32px;
}
section.introduce .info_2 .list .item .mask .common_text {
  margin-top: 16px;
  display: flex;
  align-items: center;
  font-size: 16px;
}
section.introduce .info_2 .list .item .mask .common_text svg {
  width: 24px;
  height: 24px;
}
section.introduce .info_2 .list .big {
  grid-column: span 2;
  grid-row: span 2;
  overflow: hidden;
}
section.bottom {
  margin-top: 150px;
  position: relative;
  font-size: 0;
}
section.bottom img {
  width: 100%;
}
section.bottom .content {
  color: white;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 50vw;
  min-width: 570px;
}
section.bottom .content .title {
  font-weight: 400;
  font-size: 38px;
  color: #FFFFFF;
  text-align: center;
}
section.bottom .content .des {
  width: 600px;
  height: 46px;
  font-family: Microsoft YaHei, Microsoft YaHei;
  font-weight: 400;
  font-size: 18px;
  color: #FFFFFF;
  line-height: 23px;
  text-align: center;
  margin: 0 auto;
  margin-top: 25px;
}
section.bottom .content #download_button {
  border: 2px solid #fff;
  width: fit-content;
  text-align: center;
  padding: 0 20px;
  height: 40px;
  line-height: 40px;
  color: #fff;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  opacity: 0;
  animation: show 0.5s linear forwards;
  animation-delay: 0.7s;
  margin: 0 auto;
  margin-top: 50px;
}
section.bottom .content #download_button span {
  position: relative;
  z-index: 2;
  transition: all 0.3s ease-in-out;
  font-size: 18px;
}
section.bottom .content #download_button::after {
  content: '';
  position: absolute;
  top: -100%;
  left: 0;
  width: 100%;
  height: 100%;
  background: #FFF;
  transition: all 0.3s ease-in-out;
}
section.bottom .content #download_button:hover::after {
  top: 0;
}
section.bottom .content #download_button:hover span {
  color: #1A73E8;
}
footer {
  background-color: #222222;
  color: #A4A4A4;
  padding: 15px;
}
footer .container {
  display: flex;
  gap: 20px;
  justify-content: center;
  font-size: 14px;
}
footer .container a {
  color: inherit;
}
footer .container div::after {
  content: '';
  height: 10px;
  border-right: 1px solid #A4A4A4;
  margin-left: 20px;
}
footer .container div:last-of-type::after {
  display: none;
}