:root {
  --bg: #f5f6f8;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --primary: #2196f3;
  --banner-h: 52px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

.app-banner {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: var(--banner-h);
  padding: 10px 16px;
  background: linear-gradient(90deg, #1e3a5f, #0f172a);
  color: #fff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.12);
}

.app-banner p {
  margin: 0;
  font-size: 13px;
  opacity: 0.95;
}

.app-banner .actions {
  display: flex;
  flex-shrink: 0;
  gap: 8px;
}

.btn {
  border: none;
  border-radius: 8px;
  padding: 8px 14px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.5);
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 16px;
}

.card {
  background: var(--card);
  border-radius: 12px;
  padding: 16px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
  margin-bottom: 16px;
}

.card h1 {
  margin: 0 0 8px;
  font-size: 20px;
  line-height: 1.3;
}

.meta {
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 12px;
}

.content-preview {
  font-size: 15px;
  color: #374151;
  white-space: pre-wrap;
  word-break: break-word;
}

.group-head {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}

.group-head img {
  width: 64px;
  height: 64px;
  border-radius: 12px;
  object-fit: cover;
  background: #e5e7eb;
}

.error {
  color: #b91c1c;
  padding: 16px;
}

.loading {
  text-align: center;
  padding: 48px 16px;
  color: var(--muted);
}

footer {
  text-align: center;
  font-size: 12px;
  color: var(--muted);
  padding: 24px 16px 40px;
}

  /* 首页介绍（直接访问、无分享参数） */
.intro-wrap {
  padding-bottom: 24px;
}

.intro-hero {
  text-align: center;
  padding: 28px 12px 8px;
}

.intro-hero h1 {
  margin: 0 0 12px;
  font-size: 26px;
  font-weight: 800;
  letter-spacing: 0.02em;
  background: linear-gradient(120deg, #1e40af, #0d9488);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.intro-hero .lead {
  margin: 0 auto;
  max-width: 28em;
  font-size: 16px;
  color: var(--muted);
  line-height: 1.65;
}

.intro-card {
  margin-top: 20px;
  text-align: left;
}

.intro-card h2 {
  margin: 0 0 12px;
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
}

.intro-list {
  margin: 0;
  padding-left: 1.15em;
  color: #374151;
  font-size: 15px;
  line-height: 1.75;
}

.intro-list li {
  margin-bottom: 6px;
}

.intro-note {
  margin-top: 18px;
  padding: 12px 14px;
  font-size: 13px;
  color: var(--muted);
  background: rgba(33, 150, 243, 0.08);
  border-radius: 10px;
  border-left: 3px solid var(--primary);
}