* {
  padding: 0;
  margin: 0;
}
body {
  background: #ff5555;
  overflow: hidden;
  margin: 0;
  /* background-color: #000 !important; */
}
/**
* 主容器
*/
div#main {
  width: 100vw;
  height: 100vh;
}

/**
* 设置无限的动效
* 单次动效时间3s
*/

heart {
    position: absolute;
    width: 20px;
    height: 20px;
    color: #FFF;
    background: url('heart.png') no-repeat center center;
    background-size: contain;
    opacity: 1; /* 初始不透明 */
    will-change: opacity; /* 优化动画性能 */
}

/**
* 用伪类在heart  content即是展示的文字效果
*/
heart::before {
  position: absolute;
  content: 'Miss You, YSM';
  width: 200px;
  height: 20px;
  /* background: #e74c3c; */
  border-radius: 50%;
  transform: translateX(-10px);
}

/**
*用伪类在heart
*/

heart::after {
  position: absolute;
  content: '';
  width: 20px;
  height: 20px;
  /* background: #e74c3c; */
  border-radius: 50%;
  transform: translateY(-10px);
}

/**
* 改变透明度
*/
@keyframes opacity {
  25%,
  75% {
      opacity: 1;
  }
  50%,
  100% {
      opacity: .5;
  }
}