/* 1. 主题变量与基础设置 */
:root {
  --primary: #0078ff;
  --primary-light: #e6f2ff;
  --secondary: #f5f6fa;
  --card-bg: #fff;
  --nav-bg: rgba(245, 246, 250, 0.85);
  --border-radius: 18px;
  --shadow: 0 2px 12px rgba(0,0,0,0.08);
  --active: #0078ff;
  --inactive: #888;
  --glass-blur: blur(10px);
  --transition: 0.22s cubic-bezier(.4,0,.2,1);
}

/* 2. 全局布局与字体 */
body {
  margin: 0;
  font-family: 'Segoe UI', 'PingFang SC', 'Hiragino Sans', 'Arial', sans-serif;
  background: var(--secondary);
  color: #222;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background var(--transition);
}

/* 3. 顶部导航栏 */
header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--card-bg);
  padding: 0.5rem 1.5rem;
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 10;
  transition: box-shadow var(--transition), background var(--transition);
}
.user-area {
  display: flex;
  align-items: center;
}
.avatar {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: #e0e0e0;
  overflow: hidden;
  margin-right: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  box-shadow: 0 1px 4px rgba(0,120,255,0.06);
  transition: box-shadow var(--transition);
}
.avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.username {
  font-weight: 600;
  font-size: 1.1rem;
  margin-right: 0.5rem;
}
.user-status {
  font-size: 0.9rem;
  color: #888;
  background: #f0f2f5;
  border-radius: 8px;
  padding: 2px 8px;
}
.settings-btn {
  font-size: 1.7rem;
  color: #888;
  cursor: pointer;
  transition: color var(--transition);
}
.settings-btn:hover {
  color: var(--primary);
}

/* 4. 主内容区 */
main {
  flex: 1 1 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1.5rem 1rem 4.5rem 1rem;
  box-sizing: border-box;
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  transition: padding var(--transition);
}
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  width: 100%;
  margin-top: 2rem;
  transition: gap var(--transition);
}
.feature-card {
  background: var(--card-bg);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  padding: 2rem 1.2rem 1.2rem 1.2rem;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  transition: box-shadow var(--transition), transform var(--transition);
  cursor: pointer;
  min-height: 180px;
  will-change: transform;
  text-decoration: none;
}
.feature-card:hover,
.feature-card:focus-visible {
  box-shadow: 0 6px 24px rgba(0,120,255,0.16);
  transform: scale(1.045);
  z-index: 2;
}
.feature-card * {
  text-decoration: none !important;
}
.feature-icon {
  font-size: 2.5rem;
  color: var(--primary);
  margin-bottom: 1rem;
  transition: color var(--transition);
}
.feature-title {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}
.feature-desc {
  font-size: 1rem;
  color: #666;
  flex: 1 1 auto;
}

/* 5. 底部导航栏 */
nav.bottom-nav {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  height: 60px;
  background: var(--nav-bg);
  display: flex;
  justify-content: space-around;
  align-items: center;
  box-shadow: 0 -2px 8px rgba(0,0,0,0.06);
  z-index: 20;
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-top: 1px solid #e6eaf0;
  transition: background var(--transition), box-shadow var(--transition);
}
.nav-btn {
  flex: 1 1 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: var(--inactive);
  font-size: 1.2rem;
  cursor: pointer;
  transition: color var(--transition), background var(--transition), transform var(--transition);
  padding: 0.3rem 0;
  border-radius: 12px;
  user-select: none;
  outline: none;
}
.nav-btn.active,
.nav-btn:active,
.nav-btn:focus-visible {
  color: var(--active);
  background: var(--primary-light);
  transform: scale(1.08);
}
.nav-btn .nav-icon {
  font-size: 1.7rem;
  margin-bottom: 2px;
}
.nav-btn .nav-label {
  font-size: 0.9rem;
  font-weight: 500;
}

/* 6. 响应式断点 */
@media (max-width: 767px) {
  main {
    padding: 1rem 0.3rem 4.5rem 0.3rem;
  }
  .card-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  .feature-card {
    min-height: 140px;
    padding: 1.2rem 0.8rem 0.8rem 0.8rem;
    /* 触摸目标优化 */
    min-width: 44px;
    min-height: 44px;
    /* 触摸反馈 */
    transition: background 0.18s, box-shadow 0.18s, transform 0.18s;
  }
  header {
    padding: 0.5rem 0.7rem;
  }
  /* 用户区域移动端布局优化 */
  .user-area {
    flex-direction: row;
    gap: 0.5rem;
    padding: 0.4em 0.2em;
    min-width: 44px;
    min-height: 44px;
    border-radius: 12px;
    background: var(--card-bg);
    box-shadow: 0 1px 4px rgba(0,120,255,0.04);
    transition: background 0.18s, box-shadow 0.18s;
  }
  .user-area:active,
  .user-area.active {
    background: var(--primary-light);
    box-shadow: 0 2px 8px rgba(0,120,255,0.10);
  }
  .avatar {
    width: 38px;
    height: 38px;
    font-size: 1.5rem;
    margin-right: 0.5rem;
  }
  .settings-btn {
    font-size: 1.3rem;
    margin-left: 0.3rem;
  }
  .username {
    font-size: 1rem;
    margin-right: 0.3rem;
  }
  .user-status {
    font-size: 0.85rem;
    padding: 2px 6px;
  }
  /* 底部导航触摸区域优化 */
  nav.bottom-nav {
    height: 64px;
    padding: 0 2px;
  }
  .nav-btn {
    min-width: 44px;
    min-height: 44px;
    border-radius: 14px;
    font-size: 1.15rem;
    padding: 0.2rem 0;
    transition: background 0.18s, color 0.18s, transform 0.18s;
    /* 触摸反馈 */
  }
  .nav-btn:active,
  .nav-btn.active {
    background: var(--primary-light);
    color: var(--active);
    box-shadow: 0 2px 8px rgba(0,120,255,0.10);
    transform: scale(1.08);
  }
  /* 功能卡片触摸反馈 */
  .feature-card:active,
  .feature-card.active {
    background: var(--primary-light);
    box-shadow: 0 2px 8px rgba(0,120,255,0.10);
    transform: scale(1.03);
    outline: none;
  }
}

/* 4. 全局触摸反馈：所有可交互元素 */
button:active,
input[type="button"]:active,
input[type="submit"]:active,
a:active,
[role="button"]:active {
  background: var(--primary-light);
  color: var(--active);
  box-shadow: 0 2px 8px rgba(0,120,255,0.10);
  outline: none;
  transition: background 0.18s, color 0.18s, box-shadow 0.18s;
}

/* 7. 交互动画与加载状态 */
.feature-card,
.nav-btn {
  transition: box-shadow var(--transition), color var(--transition), background var(--transition), transform var(--transition);
}
@keyframes loading-spin {
  0% { transform: rotate(0deg);}
  100% { transform: rotate(360deg);}
}
.loading-spinner {
  display: inline-block;
  width: 28px;
  height: 28px;
  border: 3px solid var(--primary-light);
  border-top: 3px solid var(--primary);
  border-radius: 50%;
  animation: loading-spin 1s linear infinite;
  margin: 0 auto;
}

/* 8. 可访问性优化 */
.feature-card:focus-visible,
.nav-btn:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}