* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: "Microsoft YaHei", sans-serif;
}
/* 全局链接统一重置 解决加a标签样式错乱 */
a {
    color: inherit;
    text-decoration: none;
}
a:hover {
    color: var(--tsinghua-purple);
    text-decoration: none;
}
/* 清华主色调 */
:root {
            --tsinghua-purple: #6E0099;
            --tsinghua-light: #9B38BB;
            --tsinghua-dark: #4D0066;
            --white: #fff;
            --gray: #f5f5f5;
            --border: #eee;
}

body {
            background-color: #f9f9f9;
}

/* 顶部LOGO */
.header {
            background-color: var(--tsinghua-purple);
            color: var(--white);
            padding: 20px 0;
            text-align: center;
            box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.logo {
            font-size: 28px;
            font-weight: bold;
            letter-spacing: 1px;
}

        /* Banner */
       /* Banner 自适应图片模式 */


/* Banner 关键修复：手机不留白 */
.banner {
    width: 100%;
    margin: 0;
    padding: 0;
    line-height: 0;
}
/* 默认隐藏手机图 */
.m-banner {
    display: none;
}
/* 电脑端：显示大图 1200px居中 */
.pc-banner {
    display: block;
    max-width: 1200px;
    width: 100%;
    height: auto;
    margin: 0 auto;
}

/* 手机端：隐藏电脑大图，只显示手机专用图 */
@media (max-width: 768px) {
    .pc-banner {
        display: none;
    }
    .m-banner {
        display: block;
        width: 100%;
        height: 200px; /* 你可以自己改：180 / 200 / 220 */
        object-fit: cover;
    }
}


        /* 导航 */
        .nav {
            background: var(--tsinghua-purple);
            box-shadow: 0 3px 12px rgba(0,0,0,0.15);
            position: relative;
            z-index: 99;
        }

        .nav-menu {
            max-width: 1200px;
            margin: 0 auto;
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            list-style: none;
        }

        .nav-menu a {
            display: inline-block;
            color: var(--white);
            text-decoration: none;
            font-size: 15px;
            font-weight: 500;
            padding: 16px 18px;
            transition: all 0.3s ease;
        }

        .nav-menu a:hover {
            background: rgba(255,255,255,0.15);
            color: #ffd700;
            transform: translateY(-1px);
        }

        /* 主体布局 */
        .container {
            max-width: 1200px;
            width: 100%;
            margin: 30px auto;
            display: flex;
            flex-wrap: wrap;
            gap: 25px;
            padding: 0 15px;
        }

        /* 左侧课程列表 */
        .left-box {
            flex: 1;
            min-width: 300px;
            background: var(--white);
            border-radius: 12px;
            padding: 10px;
            box-shadow: 0 5px 20px rgba(0,0,0,0.06);
        }

        .class-title {
            font-size: 22px;
            color: var(--tsinghua-purple);
            margin-bottom: 20px;
            padding-bottom: 10px;
            border-bottom: 3px solid var(--tsinghua-purple);
            font-weight: bold;
        }

        .course-category {
            font-size: 17px;
            font-weight: bold;
            color: var(--tsinghua-purple);
            margin: 25px 0 10px 0;
            padding-left: 12px;
            border-left: 5px solid var(--tsinghua-purple);
        }
        .course-category:first-of-type {
            margin-top: 0 !important;
        }

        /* ================= 核心修复：不用表格，改用自适应布局 ================= */
        .course-item {
            display: grid;
            grid-template-columns: 1.9fr 1.7fr 0.5fr 0.5fr;
            align-items: center;
            padding: 11px 12px;
            border-bottom: 1px solid var(--border);
            font-size: 14px;
        }
        .course-head {
            background: var(--tsinghua-light);
            color: #fff;
            font-weight: bold;
            border-radius: 6px 6px 0 0;
        }
        .course-list:hover {
            background: #f8f2ff;
        }
		/* 电脑端：隐藏标签 */
       .course-label {
    display: none;
}

        /* 手机端自动竖排，彻底不撑宽 */
        @media (max-width: 768px) {
            .course-item {
                grid-template-columns: 1fr;
                gap: 5px;
                padding: 12px 15px;
                border-radius: 8px;
                margin-bottom: 8px;
                border: 1px solid #eee;
            }
            .course-head {
                display: none; /* 手机端隐藏表头，更清爽 */
            }
			
            .course-label {
			     display: inline; /* 手机端显示 */
                font-size: 12px;
                color: var(--tsinghua-purple);
                font-weight: bold;
                margin-right:2px;
            }
        }
        /* ======================================================================= */

        /* 右侧 */
        .right-box {
            width: 280px;
            flex-shrink: 0;
            display: flex;
            flex-direction: column;
            gap: 20px;
        }

        .right-item {
            background: var(--white);
            border-radius: 12px;
            padding: 25px 20px;
            box-shadow: 0 5px 20px rgba(0,0,0,0.06);
            border-top: 4px solid var(--tsinghua-purple);
        }

        .right-title {
            font-size: 18px;
            color: var(--tsinghua-purple);
            margin-bottom: 18px;
            padding-bottom: 8px;
            border-bottom: 2px solid var(--tsinghua-purple);
            font-weight: bold;
        }

        .right-list {
            list-style: none;
        }

        .right-list li {
            padding: 10px 0;
            border-bottom: 1px dashed #e8e8e8;
        }

        .right-list li a {
            color: #333;
            text-decoration: none;
            font-size: 14px;
            display: block;
            transition: padding 0.2s;
        }

        .right-list li a:hover {
            color: var(--tsinghua-purple);
            padding-left: 6px;
            font-weight: 500;
        }
		
		/* 右侧课程分类：大气按钮版 */
.course-grid {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}
.course-grid li {
  padding: 0;
  border: 0 !important;
}
.course-grid li a {
  display: block;
  padding: 12px 10px;
  background: #f8f2ff;
  border: 1px solid #e8d6f2;
  border-radius: 8px;
  text-align: center;
  font-size: 14px;
  color: #6E0099;
  text-decoration: none;
  transition: all 0.25s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.course-grid li a:hover {
  background: #6E0099;
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 3px 8px rgba(110,0,153,0.15);
}
		
		

        /* 底部板块 */
        .section {
            max-width: 1200px;
            width: 100%;
            margin: 0 auto 40px;
            padding: 0 15px;
        }
        .section-title {
            font-size: 24px;
            color: var(--tsinghua-purple);
            text-align: center;
            margin-bottom: 30px;
            font-weight: bold;
            position: relative;
        }
        .section-title::after {
            content: "";
            width: 50px;
            height: 3px;
            background: var(--tsinghua-purple);
            position: absolute;
            left: 50%;
            bottom: -10px;
            transform: translateX(-50%);
        }

        /* 课堂照片 每行8个 */
        .photo-wrap {
            display: grid;
            grid-template-columns: repeat(8, 1fr);
            gap: 10px;
        }
        .photo-item {
            background: #fff;
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 2px 8px rgba(0,0,0,0.06);
        }
        .photo-item img {
            width: 100%;
            height: 100px;
            object-fit: cover;
            display: block;
        }
        .photo-info {
            padding: 8px;
            font-size: 12px;
            color: #333;
            text-align: center;
        }

        /* 授课师资 每行8个 */
        .teacher-wrap {
            display: grid;
            grid-template-columns: repeat(8, 1fr);
            gap: 10px;
        }
        .teacher-item {
            background: #fff;
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 2px 8px rgba(0,0,0,0.06);
            text-align: center;
            padding-bottom: 8px;
        }
        .teacher-item img {
            width: 100%;
            height: 120px;
            object-fit: cover;
            display: block;
        }
        .teacher-name {
            font-size: 14px;
            font-weight: bold;
            color: var(--tsinghua-purple);
            margin: 8px 0 3px;
        }
        .teacher-post {
            font-size: 11px;
            color: #666;
            margin-bottom: 5px;
        }

        /* 页脚 */
        .footer {
            background: var(--tsinghua-dark);
            color: var(--white);
            text-align: center;
            padding: 25px 15px;
            margin-top: 40px;
            font-size: 14px;
            box-shadow: 0 -3px 10px rgba(0,0,0,0.1);
        }

        /* 自适应 */
        @media (max-width: 1024px) {
            .photo-wrap, .teacher-wrap {
                grid-template-columns: repeat(4, 1fr);
            }
        }
        @media (max-width: 768px) {
            .container {
                flex-direction: column;
            }
            .right-box {
                width: 100%;
            }
            .photo-wrap, .teacher-wrap {
                grid-template-columns: repeat(3, 1fr);
            }
            .banner {
                height: 180px;
                font-size: 26px;
            }
        }
        @media (max-width: 480px) {
            .photo-wrap, .teacher-wrap {
                grid-template-columns: repeat(2, 1fr);
            }
            .nav-menu a {
                padding: 12px 10px;
                font-size: 14px;
            }
        }
		
		/* ====================== 手机底部漂浮导航 ====================== */

/* ----------------- 手机底部大气导航 ----------------- */
.mobile-footer-nav {
  display: none;
}
@media (max-width:768px) {
  .mobile-footer-nav {
    display: flex;
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 60px;
    background: #6E0099;
    z-index: 9999;
    box-shadow: 0 -3px 15px rgba(0,0,0,0.15);
  }
  body {
    padding-bottom: 70px !important;
  }
  .footer {
    padding-bottom: 20px !important;
  }

  /* 按钮 */
  .mobile-nav-btn {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 15px;
    font-weight: 500;
    text-decoration: none;
    border-right: 1px solid rgba(255,255,255,0.1);
  }
  .mobile-nav-btn:last-child {
    border-right: 0;
  }
  .mobile-nav-btn:hover {
    background: #9B38BB;
    color: #ffd700;
  }
  .mobile-nav-btn:active {
    background: #4D0066;
  }
}