/* 西南交大 2026 级铁道一班 · 课件资料共享站
   简约校园风格 · 移动端优先 · 无第三方依赖 */

:root {
  --blue: #17457e;
  --blue-dark: #0f3158;
  --blue-soft: #e8f0fa;
  --gold: #c8a35a;
  --ink: #1d2733;
  --ink-soft: #5a6b7f;
  --line: #e3e9f1;
  --bg: #f4f6f9;
  --card: #ffffff;
  --danger-soft: #fdecec;
  --danger-ink: #b03a3a;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
}

.wrap {
  max-width: 900px;
  margin: 0 auto;
  padding-left: 16px;
  padding-right: 16px;
}

/* ---------- 顶部标题 ---------- */

.site-header {
  background: var(--blue);
  border-bottom: 3px solid var(--gold);
  color: #fff;
  padding: 26px 0 20px;
}

.site-header h1 {
  margin: 0;
  font-size: 21px;
  font-weight: 600;
  letter-spacing: 0.5px;
}

.site-header .subtitle {
  margin: 6px 0 0;
  font-size: 14px;
  color: rgba(255, 255, 255, 0.85);
}

.site-header .meta-line {
  margin: 10px 0 0;
  font-size: 13px;
  color: rgba(255, 255, 255, 0.75);
}

/* ---------- 学科导航 ---------- */

.subject-nav {
  position: sticky;
  top: 0;
  z-index: 10;
  background: #fff;
  border-bottom: 1px solid var(--line);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.subject-nav::-webkit-scrollbar { display: none; }

.subject-nav .nav-inner {
  display: flex;
  gap: 8px;
  padding: 10px 16px;
  max-width: 900px;
  margin: 0 auto;
  width: max-content;
  min-width: 100%;
}

.nav-chip {
  flex: 0 0 auto;
  display: inline-block;
  padding: 5px 14px;
  border: 1px solid var(--blue);
  border-radius: 999px;
  color: var(--blue);
  font-size: 14px;
  text-decoration: none;
  white-space: nowrap;
  background: #fff;
}

.nav-chip:active {
  background: var(--blue-soft);
}

/* ---------- 主体 ---------- */

main.wrap {
  padding-top: 16px;
  padding-bottom: 24px;
}

.state-box {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 22px 16px;
  text-align: center;
  color: var(--ink-soft);
  font-size: 15px;
  margin-bottom: 16px;
}

.state-error p { margin: 0 0 12px; color: var(--danger-ink); }

.retry-btn {
  border: 1px solid var(--blue);
  background: #fff;
  color: var(--blue);
  border-radius: 8px;
  padding: 8px 22px;
  font-size: 15px;
  cursor: pointer;
}

/* ---------- 学科卡片 ---------- */

.subject-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 6px 16px 10px;
  margin-bottom: 16px;
  scroll-margin-top: 72px;
}

.subject-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px;
  padding: 12px 0 8px;
  border-bottom: 1px solid var(--line);
}

.subject-head h2 {
  margin: 0;
  font-size: 17px;
  font-weight: 600;
  color: var(--blue-dark);
  border-left: 4px solid var(--blue);
  padding-left: 10px;
  line-height: 1.3;
}

.subject-head .count {
  flex: 0 0 auto;
  font-size: 13px;
  color: var(--ink-soft);
}

/* ---------- 文件列表 ---------- */

.file-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.file-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--line);
}

.file-item:last-child { border-bottom: none; }

.file-badge {
  flex: 0 0 auto;
  width: 46px;
  height: 46px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.3px;
  background: var(--blue-soft);
  color: var(--blue);
  text-transform: uppercase;
}

.file-badge.b-pdf  { background: var(--danger-soft); color: var(--danger-ink); }
.file-badge.b-ppt  { background: #fdf0e3; color: #b06a1f; }
.file-badge.b-doc  { background: #e8f0fa; color: #2b5aa0; }
.file-badge.b-xls  { background: #e7f5ec; color: #237a46; }
.file-badge.b-zip  { background: #f0ecf9; color: #5b3fa8; }
.file-badge.b-img  { background: #eaf6f6; color: #1f7a7a; }

.file-info {
  flex: 1 1 auto;
  min-width: 0;
}

.file-name {
  font-size: 15px;
  color: var(--ink);
  word-break: break-all;
  line-height: 1.45;
}

.file-meta {
  margin-top: 2px;
  font-size: 12px;
  color: var(--ink-soft);
}

.download-btn {
  flex: 0 0 auto;
  display: inline-block;
  background: var(--blue);
  color: #fff;
  text-decoration: none;
  font-size: 14px;
  padding: 9px 18px;
  border-radius: 8px;
  white-space: nowrap;
}

.download-btn:active { background: var(--blue-dark); }

/* 预览 / 下载 两个入口并排：预览为描边，下载为实心 */
.file-actions {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 8px;
}

.preview-btn {
  display: inline-block;
  background: #fff;
  color: var(--blue);
  border: 1px solid var(--blue);
  text-decoration: none;
  font-size: 14px;
  padding: 8px 14px;
  border-radius: 8px;
  white-space: nowrap;
}

.preview-btn:active { background: var(--blue-soft); }

.empty-box {
  padding: 18px 0 14px;
  text-align: center;
  color: #9aa8b8;
  font-size: 14px;
}

/* ---------- 页脚 ---------- */

.site-footer {
  border-top: 1px solid var(--line);
  background: #fff;
  padding: 18px 0 calc(18px + env(safe-area-inset-bottom));
  text-align: center;
}

.site-footer p {
  margin: 0;
  font-size: 13px;
  color: var(--ink-soft);
}

.site-footer .footer-tip {
  margin-top: 4px;
  color: #9aa8b8;
  font-size: 12px;
}

/* ---------- 桌面端微调 ---------- */

@media (min-width: 720px) {
  .site-header { padding: 34px 0 26px; }
  .site-header h1 { font-size: 26px; }
  .site-header .subtitle { font-size: 15px; }
  .file-badge { width: 50px; height: 50px; font-size: 12px; }
  .file-name { font-size: 16px; }
}