/* Слой снега */
#snow-layer {
  pointer-events: none;
  position: fixed;
  inset: 0;
  z-index: 9999;
  overflow: hidden;
}

/* Одна снежинка */
.snowflake {
  position: absolute;
  top: -10px;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: #fff;
  opacity: 0.8;
  filter: drop-shadow(0 0 4px rgba(255,255,255,0.9));
  will-change: transform;
  animation-name: snow-fall;
  animation-timing-function: linear;
  animation-iteration-count: 1;
}

/* небольшая вариация размеров */
.snowflake.small  { width: 2px; height: 2px; opacity: .6; }
.snowflake.big    { width: 6px; height: 6px; opacity: 1;  }

/* падение + лёгкое покачивание */
@keyframes snow-fall {
  0% {
    transform: translate3d(0, -10px, 0);
  }
  100% {
    transform: translate3d(var(--sx, 0px), 110vh, 0);
  }
}