.snow {
    /*雪の色*/
    color: snow;
    /*雪の大きさ*/
    font-size: 15px;
    /*初期位置*/
    position: fixed;
    top: -5%;
    /*雪を適当な幅で降らせる*/
    text-shadow:
    5vw   -100px 2px,
    10vw  -400px 3px,
    20vw  -500px 4px,
    30vw  -580px 1px,
    39vw  -250px 2px,
    42vw  -340px 5px,
    56vw  -150px 2px,
    63vw  -180px 0,
    78vw  -220px 4px,
    86vw  -320px 9px,
    94vw  -170px 7px;
    /*雪アニメーション1*/
    animation: roll 5s linear infinite;
  }
    /*2つめの雪アニメーション*/
  .snow2nd{animation: anim 8s linear infinite;}
  
  @keyframes roll {
      0% {transform:rotate(0deg);}
     90% {opacity:1;}
     100% {transform:rotate(20deg);top:100%;opacity:0;}
  }
  @keyframes anim {
    100% {color:transparent;top:150%;}
  }