/* =========================
   全局重置
   ========================= */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* =========================
   深色背景 + 居中布局
   ========================= */
body {
  background-color: #0f172a; /* 深邃蓝黑 */
  color: #e5e7eb;           /* 浅灰白字，比纯白柔和 */
  font-family: "Microsoft YaHei", sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;        /* 撑满全屏高度 */
  padding: 20px;
}

/* =========================
   内容卡片容器
   ========================= */
.container {
  max-width: 600px;
  text-align: center;
  background: #1e293b;      /* 卡片深灰色 */
  padding: 40px;
  border-radius: 12px;
  box-shadow: 0 10px 25px rgba(0,0,0,0.5);
}

/* =========================
   首页标题
   ========================= */
.WelcomeTextTitle {
  font-size: 36px;
  color: #38bdf8;           /* 亮蓝色标题 */
  margin-bottom: 20px;
}

/* =========================
   普通说明文字
   ========================= */
.AboutInfoText {
  font-size: 16px;
  line-height: 1.6;         /* 行高，让文字不那么挤 */
  margin-bottom: 12px;
  color: #94a3b8;           /* 次级文字颜色 */
}

.AboutInfoText a {
  color: #3b82f6;
  text-decoration: none;
  transition: color 0.3s;
}
.AboutInfoText a:hover {
  color: #60a5fa;
  text-decoration: underline;
}

/* =========================
   自我介绍栏
   ========================= */
.intro {
  margin-top: 36px;
  padding-top: 28px;
  border-top: 1px solid #334155; /* 用一根细线把上下两区分开 */
  text-align: left;              /* 自我介绍左对齐，读着舒服 */
}

.IntroTitle {
  font-size: 22px;
  color: #38bdf8;
  margin-bottom: 14px;
  text-align: center;
}

.IntroText {
  font-size: 15px;
  line-height: 1.8;
  color: #cbd5e1;
  margin-bottom: 12px;
}

.IntroEmail {
  color: #3b82f6;
  text-decoration: none;
  border-bottom: 1px dashed #3b82f6; /* 虚线，暗示“可点击” */
  transition: color 0.3s;
}
.IntroEmail:hover {
  color: #60a5fa;
}

/* =========================
   导航按钮（已修正）
   ========================= */
.nav-buttons {
  margin-top: 36px;
  text-align: center;
  /* 已移除 fixed 定位，按钮会自然排在内容下方 */
}

.btn-primary {
  display: inline-block;
  padding: 14px 32px;
  background: #3b82f6;
  color: white;
  text-decoration: none;
  border-radius: 8px;
  font-size: 16px;
  font-weight: bold;
  transition: background 0.3s, transform 0.2s;
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
}
.btn-primary:hover {
  background: #2563eb;
  transform: scale(1.05);
}

/* =========================
   视频网格布局
   ========================= */
.video-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);  /* 两列 */
  gap: 20px;
  margin-top: 28px;
}

/* 单个视频卡片 */
.video-card {
  display: block;
  background: #1e293b;
  border: 1px solid #334155;
  border-radius: 12px;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  color: #e5e7eb;
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}
.video-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 20px rgba(56, 189, 248, 0.2);
  border-color: #38bdf8;
}

/* 缩略图占位（先用 emoji 顶着，以后换真图） */
.video-thumb {
  font-size: 48px;
  margin-bottom: 12px;
}

/* 视频标题 */
.video-title {
  font-size: 15px;
  color: #94a3b8;
}