.first-loading-box {
  height: 100vh;
  width: 100vw;
  /*display: grid;*/
  /*grid-template-rows: repeat(3, 33.33vh);*/
  /*grid-template-columns: repeat(4, 25vw);*/
  display: flex;
  justify-content: center;
  align-items: center;
}

.first-loading-box > .loading-item {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.first-loading-box > .loading-item > h1 {
  height: 3.6vw;
  line-height: 3.6vw;
  font-size: 1.8vw;
  font-weight: bolder;
  color: rgba(0, 0, 0, 0.65);
  /*filter: blur(0.5px);*/
}

/*  ① two-balls start
------------------------------------------------ */
.first-loading-box .two-balls {
  width: 2.6vw;
  height: 3.2vw;
  position: relative;
  padding-top: 1vw;
}

.two-balls > div {
  position: absolute;
  width: 1.1vw;
  height: 1.1vw;
  border-radius: 50%;
  animation: two-balls-pink 0.8s ease-in-out infinite;
}

.two-balls .ball-pink {
  background: #ff4a69;
  left: -0.2vw;
}

.two-balls .ball-blue {
  background: #1342ed;
  right: -0.2vw;
  /* infinite：动画重复播放 */
  animation: two-balls-blue 0.8s ease-in-out infinite;
}

@keyframes two-balls-pink {
  from {
    z-index: 1;
  }
  50% {
    transform: translateX(1.8vw);
  }
}

@keyframes two-balls-blue {
  50% {
    transform: translateX(-1.8vw);
  }
}
/*  ① two-balls end
------------------------------------------------ */

/*  ② three-balls-bounce start
------------------------------------------------ */
.three-balls-bounce {
  position: relative;
  width: 10.5vw;
  height: 3.2vw;
}

.three-balls-bounce .ball-circle {
  width: 1.1vw;
  height: 1.1vw;
  border-radius: 50%;
  background: #ff4569;
  position: absolute;
  left: 15%;
  transform-origin: 50%;
  /* alternate: 偶数次动画反向播放 */
  animation: balls-circle 0.5s ease-in-out infinite alternate;
}

.three-balls-bounce .ball-shadow {
  width: 1.1vw;
  height: 0.22vw;
  border-radius: 50%;
  background: rgba(0, 0, 0, 0.4);
  position: absolute;
  top: 3.2vw;
  left: 15%;
  transform-origin: 50%;
  /* alternate: 偶数次动画反向播放 */
  animation: balls-shadow 0.5s ease-in-out infinite alternate;
  z-index: -1;
  filter: blur(1px);
}
.three-balls-bounce .ball-circle:nth-child(2) {
  background: #1342ed;
}
.three-balls-bounce .ball-circle:nth-child(2),
.three-balls-bounce .ball-shadow:nth-child(5) {
  left: 45%;
  animation-delay: 0.2s;
}

.three-balls-bounce .ball-circle:nth-child(3) {
  background: #fabe02;
}
.three-balls-bounce .ball-circle:nth-child(3),
.three-balls-bounce .ball-shadow:nth-child(6) {
  left: auto;
  right: 15%;
  animation-delay: 0.3s;
}

@keyframes balls-circle {
  from {
    top: 3.2vw;
    height: 0.22vw;
    border-radius: 2.4vw 2.4vw 1.2vw 1.2vw;
    transform: scaleX(1.7);
  }
  40% {
    height: 1.1vw;
    border-radius: 50%;
    transform: scaleX(1);
  }
  to {
    top: 0px;
  }
}

@keyframes balls-shadow {
  from {
    transform: scaleX(1.5);
  }
  40% {
    opacity: 0.7;
    transform: scaleX(1);
  }
  to {
    opacity: 0.4;
    transform: scaleX(0.2);
  }
}

/*  ② three-balls-bounce end
------------------------------------------------ */

/*  ③ rainbow start
------------------------------------------------ */
.rainbow-waves .rainbow-waves-item {
  background-color: var(--bg-color);
  display: inline-block;
  width: 0.22vw;
  height: 2.5vw;
  border-radius: 999px;
  /* alternate-reverse: 奇数次动画反向播放，偶数次动画正向播放 */
  animation: rainbow-waves 0.5s linear infinite alternate-reverse;
  animation-delay: calc(var(--i));
}

.rainbow-waves-item + .rainbow-waves-item {
  margin-left: 0.5vw;
}

@keyframes rainbow-waves{
    from {
        transform: scale(1, 0.2);
    }
    to {
        transform: scale(1, 1);
    }
}
/*  ③ rainbow end
------------------------------------------------ */