h1 {
    font-size: 4em;
    color: #cc0000;
    text-shadow:
        0 0 5px #ff0000,
        0 0 10px #ff0000,
        0 0 20px #990000,
        0 8px 0 #660000;
    letter-spacing: 5px;
}
body {
    margin: 0;
    font-family: sans-serif;
    background: #111;
    color: white;
    text-align: center;
    overflow-x: hidden;
}

/* 霧 */
body::before,
body::after {
    content: "";
    position: fixed;
    top: 0;
    left: -50%;
    width: 200%;
    height: 100%;
    pointer-events: none;
    z-index: -1;

    background:
        radial-gradient(circle, rgba(255,255,255,0.08) 0%, transparent 60%),
        radial-gradient(circle, rgba(255,255,255,0.05) 0%, transparent 50%);

    background-size: 400px 400px, 300px 300px;
    animation: fogMove 40s linear infinite;
}

body::after {
    opacity: 0.5;
    animation-duration: 60s;
    animation-direction: reverse;
}

@keyframes fogMove {
    from {
        transform: translateX(0);
    }
    to {
        transform: translateX(25%);
    }
}
body {
    background:
        radial-gradient(circle at center,
        #330000 0%,
        #1a0000 30%,
        #000000 100%);
}
#menu{
  display:none;
  margin-top:20px;
  padding:20px;
  background:#222;
  color:white;
  border:2px solid darkred;
}

.menu-btn{
  padding:15px 30px;
  font-size:20px;
  background:darkred;
  color:white;
  border:none;
  cursor:pointer;
}

.hero-image{
    width: 100%;
    max-width: 1200px;
    display: block;
    margin: 0 auto;

    border-radius: 20px;

    box-shadow:
        0 0 20px rgba(255,0,0,.5),
        0 0 50px rgba(255,0,0,.3);

    animation: imageGlow 4s infinite alternate;
}

@keyframes imageGlow{
    from{
        filter: brightness(0.9);
    }
    to{
        filter: brightness(1.1);
    }
}

header {
  animation: fadeIn 2s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(-50px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

header {
  animation: fadeIn 2s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(-50px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

}
.moon{
  position:fixed;
  top:50px;
  right:50px;
  width:120px;
  height:120px;
  border-radius:50%;
  background:#fff8dc;
  box-shadow:0 0 50px #fff8dc;
  opacity:.8;
  z-index:-2;
}
.moon{
  z-index: -1
   ;
}

.stars{
  position: fixed;
  inset: 0;
  pointer-events: none;

  background-image:
    radial-gradient(white 1px, transparent 1px),
    radial-gradient(white 1.5px, transparent 1.5px),
    radial-gradient(white 2px, transparent 2px);

  background-size:
    180px 180px,
    320px 320px,
    500px 500px;

  background-position:
    0 0,
    50px 120px,
    200px 80px;

  animation: twinkle 6s infinite alternate;
  opacity: .4;
}
background-image:
  radial-gradient(#d8e6ff 1.5px, transparent 1.5px);

.moon{
  position: fixed;
  top: 50px;
  right: 50px;
  width: 120px;
  height: 120px;
  border-radius: 50%;
  background: #fff8dc;
  box-shadow: 0 0 50px #fff8dc;
  cursor: pointer;
  transition: 1s;
}

.blood-moon{
  background: #aa0000;
  box-shadow: 0 0 80px red;
}

.moon{
  position: fixed;
  top: 50px;
  right: 50px;
  width: 120px;
  height: 120px;
  border-radius: 50%;
  background: #fff8dc;
  box-shadow: 0 0 50px #fff8dc;

  cursor: pointer;
  transition: all 2s ease;
}

.moon::after{
  content:"";
  position:absolute;
  inset:0;
  border-radius:50%;
  background:#8b0000;

  opacity:0;
  transition:opacity 2s ease;
}

.moon.eclipse{
  transform:scale(1.15);
  box-shadow:
    0 0 30px #ff0000,
    0 0 80px #ff0000,
    0 0 150px #660000;
}

.moon.eclipse::after{
  opacity:.85;
}
body{
  transition:background 3s ease;
}

body.blood-night{
  background:
    radial-gradient(circle at center,
    #330000 0%,
    #120000 50%,
    #000000 100%);
}

.hidden-box{
  display:none;

  margin:20px auto;
  max-width:700px;

  padding:20px;

  background:rgba(20,20,20,.85);

  border:1px solid #660000;
  border-radius:15px;

  animation:fadeIn .5s;
}

@keyframes fadeIn{
  from{
    opacity:0;
    transform:translateY(-20px);
  }
  to{
    opacity:1;
    transform:translateY(0);
  }
}