body {
  max-width: 800px;
  margin: auto;
  padding: 1em;
  font-size: 17px;
  line-height: 1.7;
  background-color: #ffffff;  /*  rgba(255,255,255,0.95) */
  position: relative;         /* 确保背景层正常显示 */
}

/* background */
.background-logo {
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  background-image: url("ucas2.png");
  background-size: 22%;
  background-position: center center;
  background-repeat: no-repeat;
  opacity: 0.05;            /* transparent */
  z-index: -1;              /* background */
  pointer-events: none;     /* do not influence pointer behavior */
}




/* header and footer areas */
.menu { padding: 0; }
.menu li { display: inline-block; }
.article-meta, .menu a {
  text-decoration: none;
  background: #eee;
  padding: 5px;
  border-radius: 5px;
}
.menu, .article-meta, footer { text-align: center; }
.title { font-size: 1.1em; }
footer a { text-decoration: none; }
hr {
  border-style: dashed;
  color: #ddd;
}

/* code */
pre {
  border: 1px solid #ddd;
  box-shadow: 5px 5px 5px #eee;
  padding: 1em;
  overflow-x: auto;
}
code { background: #f9f9f9; }
pre code { background: none; }

/* misc elements */
img, iframe, video { max-width: 100%; }
main { hyphens: auto; }
blockquote {
  background: #f9f9f9;
  border-left: 5px solid #ccc;
  padding: 3px 1em 3px;
}

table {
  margin: auto;
  border-top: 1px solid #666;
  border-bottom: 1px solid #666;
}
table thead th { border-bottom: 1px solid #ddd; }
th, td { padding: 5px; }
thead, tfoot, tr:nth-child(even) { background: #eee; }




.classic-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid black;
  padding: 10px 0;
  margin-top: 80px; /* 离页面顶部空出更多 */
  position: relative;
  background-color: white;
}

/* 左上角装饰 */
.classic-nav::before {
  content: "";
  position: absolute;
  top: -15px;
  left: -15px;
  width: 20px;
  height: 20px;
  border-left: 1px solid black;
  border-top: 1px solid black;
}

/* 右上角装饰 */
.classic-nav::after {
  content: "";
  position: absolute;
  top: -15px;
  right: -15px;
  width: 20px;
  height: 20px;
  border-right: 1px solid black;
  border-top: 1px solid black;
}


.nav-logo img {
  height: 45px;  /* 或者你想要的尺寸，例如 32px、48px */
  width: auto;   /* 保持图片原始比例 */
  margin-left: 10px; /* 与左边缘留白 */
}
.nav-logo-text {
  /* background-color: #8C1515;   Stanford Cardinal Red */
  /* color: white;                White text */
  font-weight: bold;
  font-size: 20px;
  width: 40px;
  height: 40px;
  border-radius: 50%;          /* Circle shape */
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Georgia', serif;
  margin-right: 20px;
}



.nav-menu {
  font-size: 18px;  
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-menu li {
  margin: 0 10px;
  position: relative;
}

.nav-menu a {
  color: black;
  text-decoration: none;
  font-weight: bold;
  padding-bottom: 5px;
}

.nav-menu li.active a {
  color: #8C1515; /* Stanford red */
}


.nav-menu li.active a::after {
  content: "";
  position: absolute;
  left: 0;
  width: 100%;
  height: 3px;
  color: #8C1515; /* Stanford red */
}


a {
  color: black;
  text-decoration: underline;
  text-decoration-style: dashed;
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
}
a:hover {
  color: #8C1515;
}


.responsive-img {
  max-height: 100px;
  height: auto;
  width: auto;
}



#back-to-top {
  position: fixed;
  bottom: 40px;
  right: 30px;
  z-index: 99;
  border: none;
  outline: none;
  background-color: #8C1515;
  color: white;
  cursor: pointer;
  padding: 10px 15px;
  border-radius: 50%;
  font-size: 18px;
  display: none;
  transition: opacity 0.3s;
  font-weight: bold;
}
#back-to-top:hover {
  background-color: #a11b1b;
}