/* ============================================
   小学生防溺水知识问答 — 共享样式
   暗色深海主题 · 水面光影渐变 · 微动效
   ============================================ */

/* ---- CSS 自定义属性（主题色） ---- */
:root {
  --color-bg-deep: #0a1628;
  --color-bg-mid: #0f1f3d;
  --color-bg-card: #162a4a;
  --color-primary: #4fc3f7;
  --color-primary-glow: #29b6f6;
  --color-accent: #ffd54f;
  --color-accent-glow: #ffca28;
  --color-danger: #ef5350;
  --color-success: #66bb6a;
  --color-text: #e0e8f0;
  --color-text-dim: #90a4ae;
  --color-border: #1e3a5f;
  --color-surface: rgba(22, 42, 74, 0.85);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --shadow-card: 0 4px 20px rgba(0, 0, 0, 0.4);
  --shadow-glow: 0 0 20px rgba(79, 195, 247, 0.3);
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC",
               "Microsoft YaHei", "Helvetica Neue", sans-serif;
  background: linear-gradient(135deg, var(--color-bg-deep), var(--color-bg-mid), #0d1b2a);
  color: var(--color-text);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ---- 渐变标题 ---- */
.gradient-title {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: 800;
  letter-spacing: 0.02em;
}

/* ---- 卡片 ---- */
.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-card);
  transition: transform var(--transition), box-shadow var(--transition);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-glow);
}

.card:active {
  transform: translateY(-1px);
}

/* ---- 按钮 ---- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  color: var(--color-text);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  user-select: none;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-glow));
  color: #0a1628;
  border: none;
}

.btn-primary:hover {
  box-shadow: 0 0 25px rgba(79, 195, 247, 0.5);
}

.btn-accent {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-glow));
  color: #0a1628;
  border: none;
}

.btn-accent:hover {
  box-shadow: 0 0 25px rgba(255, 213, 79, 0.5);
}

.btn-danger {
  background: linear-gradient(135deg, var(--color-danger), #e53935);
  color: #fff;
  border: none;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
  box-shadow: none !important;
}

/* ---- 导航栏 ---- */
.nav-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: rgba(10, 22, 40, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-bar .logo {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--color-primary);
  text-decoration: none;
}

.nav-bar .nav-links {
  display: flex;
  gap: 16px;
  list-style: none;
}

.nav-bar .nav-links a {
  color: var(--color-text-dim);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color var(--transition);
}

.nav-bar .nav-links a:hover {
  color: var(--color-primary);
}

/* ---- 容器 ---- */
.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 24px 16px;
}

/* ---- 入口卡片网格 ---- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
  margin-top: 24px;
}

.card-grid .card {
  text-align: center;
  cursor: pointer;
}

.card-grid .card .card-icon {
  font-size: 3rem;
  margin-bottom: 12px;
}

.card-grid .card h3 {
  font-size: 1.15rem;
  margin-bottom: 8px;
  color: var(--color-primary);
}

.card-grid .card p {
  font-size: 0.9rem;
  color: var(--color-text-dim);
  line-height: 1.5;
}

/* ---- 返回首页链接 ---- */
.back-home {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-dim);
  text-decoration: none;
  font-size: 0.9rem;
  margin-bottom: 20px;
  transition: color var(--transition);
}

.back-home:hover {
  color: var(--color-primary);
}

/* ---- 响应式 ---- */
@media (max-width: 600px) {
  html { font-size: 14px; }
  .container { padding: 16px 12px; }
  .card-grid { grid-template-columns: 1fr; }
  .nav-bar { flex-direction: column; gap: 8px; padding: 12px 16px; }
}

/* ---- 工具类 ---- */
.text-center { text-align: center; }
.mt-8 { margin-top: 8px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mb-16 { margin-bottom: 16px; }
.fade-in { animation: fadeIn 0.5s ease forwards; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}