* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 0;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: #f5f5f5;
  font-family: 'Microsoft YaHei', 'PingFang SC', 'Helvetica Neue', Arial, sans-serif;
}

.page-title {
  position: fixed;
  top: 30px;
  left: 50%;
  transform: translateX(-50%);
  color: #333;
  font-size: 28px;
  font-weight: 300;
  text-align: center;
  z-index: 10;
}

svg {
  margin: auto;
  width: 90vmin;
  height: 65%;
  border: 4px solid black;
  background: #fff;
}

.top-cube {
  stroke-dasharray: 1600;
  stroke-dashoffset: 100%;
  -webkit-animation: anim 4s linear forwards;
          animation: anim 4s linear forwards;
}

.right-cube,
.left-cube {
  stroke-dasharray: 1760;
  stroke-dashoffset: 100%;
  -webkit-animation: anim 4s linear forwards;
          animation: anim 4s linear forwards;
}

@-webkit-keyframes anim {
  from {
    stroke-dashoffset: 100%;
  }
  to {
    stroke-dashoffset: 0;
  }
}

@keyframes anim {
  from {
    stroke-dashoffset: 100%;
  }
  to {
    stroke-dashoffset: 0;
  }
}