css3实现流星坠落效果

<div class="star"></div>
      <div class="star pink"></div>
      <div class="star blue"></div>

.star {
    display: block;
    width: 5px;
    height: 5px;
    border-radius: 50%;
    background: #FFF;
    top: 100px;
    left: 500px;
    position: relative;
    transform-origin: 100% 0;
    animation: star-ani 4s linear infinite;
    -webkit-animation:star-ani 5s linear infinite;
    box-shadow: 0 0 5px 5px rgba(255, 255, 255, .3);
    opacity: 0;
    z-index: 2;
}
.star:after {
    content: ‘‘;
    display: block;
    top: 0px;
    left: 4px;
    border: 0px solid #fff;
    border-width: 0px 90px 2px 90px;
    border-color: transparent transparent transparent rgba(255, 255, 255, .3);
    transform: rotate(-45deg) translate3d(1px, 3px, 0);
    box-shadow: 0 0 1px 0 rgba(255, 255, 255, .1);
    transform-origin: 0% 100%;
    animation: shooting-ani 3s infinite ease-out;
}
.pink {
    top: 100px;
    left: 800px;
    background: #fff;
    animation-delay: 3s;
    -webkit-animation-delay: 3s;
    -moz-animation-delay: 3s;
}
.pink:after {
    border-color: transparent transparent transparent #fff;
    animation-delay: 3s;
    -webkit-animation-delay: 3s;
    -moz-animation-delay: 3s;
}
.blue {
    top: 120px;
    left: 1200px;
    background: fff;
    animation-delay: 7s;
    -webkit-animation-delay: 7s;
    -moz-animation-delay: 7s;
}
.blue:after {
     border-color: transparent transparent transparent fff;
    -webkit-animation-delay: 7s;
    -moz-animation-delay: 7s;
    animation-delay: 7s;
}
  @keyframes star-ani {
    0% {
        opacity: 0;
        transform: scale(0) translate3d(0, 0, 0);
    }
    20%{
        opacity: 0.8;
        transform: scale(0.2) translate3d(-100px, 100px, 0);
    }
    40% {
        opacity: 0.8;
        transform: scale(0.4) translate3d(-200px, 200px, 0);
    }
    60% {
        opacity: 0.8;
        transform: scale(0.6) translate3d(-300px, 300px, 0);
    }
    80% {
        opacity: 1;
        transform: scale(1) translate3d(-350px, 350px, 0);
    }
    100% {
        opacity: 1;
        transform: scale(1.2) translate3d(-400px, 380px, 0);
    }
}