/* 雪の結晶エフェクト用CSS */
.snowflake {
  position: fixed;
  top: -10px;
  color: #e6f3ff;
  user-select: none;
  pointer-events: none;
  z-index: 1000;
  font-size: 1.8em;
  animation-name: snowfall;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
  text-shadow: 0 0 8px rgba(135, 206, 235, 0.3), 0 0 3px rgba(173, 216, 230, 0.5);
}

@keyframes snowfall {
  0% {
    transform: translateY(0) rotate(0deg);
    opacity: 1;
  }
  100% {
    transform: translateY(100vh) rotate(360deg);
    opacity: 0;
  }
}

/* 異なるサイズと速度のバリエーション */
.snowflake:nth-child(1) {
  left: 10%;
  animation-duration: 8s;
  font-size: 1.4em;
}
.snowflake:nth-child(2) {
  left: 20%;
  animation-duration: 12s;
  font-size: 1.8em;
  animation-delay: -2s;
}
.snowflake:nth-child(3) {
  left: 30%;
  animation-duration: 10s;
  font-size: 1.5em;
  animation-delay: -4s;
}
.snowflake:nth-child(4) {
  left: 40%;
  animation-duration: 15s;
  font-size: 1.7em;
  animation-delay: -1s;
}
.snowflake:nth-child(5) {
  left: 50%;
  animation-duration: 9s;
  font-size: 1.3em;
  animation-delay: -3s;
}
.snowflake:nth-child(6) {
  left: 60%;
  animation-duration: 13s;
  font-size: 1.9em;
  animation-delay: -5s;
}
.snowflake:nth-child(7) {
  left: 70%;
  animation-duration: 11s;
  font-size: 1.5em;
  animation-delay: -2.5s;
}
.snowflake:nth-child(8) {
  left: 80%;
  animation-duration: 14s;
  font-size: 1.6em;
  animation-delay: -4.5s;
}
.snowflake:nth-child(9) {
  left: 90%;
  animation-duration: 10s;
  font-size: 1.4em;
  animation-delay: -1.5s;
}
.snowflake:nth-child(10) {
  left: 5%;
  animation-duration: 16s;
  font-size: 2.0em;
  animation-delay: -6s;
}
.snowflake:nth-child(11) {
  left: 15%;
  animation-duration: 8s;
  font-size: 1.2em;
  animation-delay: -7s;
}
.snowflake:nth-child(12) {
  left: 25%;
  animation-duration: 12s;
  font-size: 1.7em;
  animation-delay: -8s;
}
.snowflake:nth-child(13) {
  left: 35%;
  animation-duration: 9s;
  font-size: 1.5em;
  animation-delay: -3.5s;
}
.snowflake:nth-child(14) {
  left: 45%;
  animation-duration: 11s;
  font-size: 1.8em;
  animation-delay: -4.8s;
}
.snowflake:nth-child(15) {
  left: 55%;
  animation-duration: 13s;
  font-size: 1.4em;
  animation-delay: -2.2s;
}
.snowflake:nth-child(16) {
  left: 65%;
  animation-duration: 10s;
  font-size: 1.6em;
  animation-delay: -5.5s;
}
.snowflake:nth-child(17) {
  left: 75%;
  animation-duration: 14s;
  font-size: 1.3em;
  animation-delay: -6.8s;
}
.snowflake:nth-child(18) {
  left: 85%;
  animation-duration: 8s;
  font-size: 1.9em;
  animation-delay: -1.8s;
}
.snowflake:nth-child(19) {
  left: 95%;
  animation-duration: 12s;
  font-size: 1.5em;
  animation-delay: -3.2s;
}
.snowflake:nth-child(20) {
  left: 3%;
  animation-duration: 15s;
  font-size: 1.7em;
  animation-delay: -4.2s;
}