/* 全局基础样式 */
body {
    font-family: 'PingFang SC', 'Microsoft YaHei', sans-serif;
    padding-bottom: 80px; /* 为底部导航腾出空间 */
    background-color: #f0f0f0;
}

/* 卡片样式 */
.feature-card, .learning-card {
    border-radius: 16px;
    transition: all 0.3s ease;
}
.feature-card:hover, .learning-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

/* 难度标签样式 */
.difficulty-badge, .badge {
    font-size: 0.7rem;
    padding: 0.2rem 0.5rem;
    border-radius: 9999px;
}
.difficulty-easy { 
    background-color: #C6F6D5; 
    color: #22543D; 
}
.difficulty-medium { 
    background-color: #FEEBC8; 
    color: #744210; 
}
.difficulty-hard { 
    background-color: #FED7D7; 
    color: #742A2A; 
}

/* 分类标签样式 */
.category-tab {
    padding: 8px 16px;
    border-radius: 16px;
    font-weight: 500;
    white-space: nowrap;
}
.category-tab.active {
    background-color: #4299e1;
    color: white;
}
.category-content {
    display: none;
}
.category-content.active {
    display: block;
}

/* 菜单项样式 */
.menu-item {
    transition: all 0.2s ease;
}
.menu-item:hover {
    background-color: #F3F4F6;
}

/* 渐变背景 */
.banner {
    background: linear-gradient(135deg, #5B86E5, #36D1DC);
}

/* 底部导航栏样式 */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: white;
    display: flex;
    justify-content: space-around;
    padding: 8px 0;
    box-shadow: 0 -2px 10px rgba(0,0,0,0.1);
    z-index: 100;
}
.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 8px 0;
    width: 50%; /* 修改宽度为50%，只有两个导航项 */
    color: #666;
    font-size: 12px;
    font-weight: 500;
}
.nav-item.active {
    color: #3182ce;
}
.nav-item i {
    font-size: 20px;
    margin-bottom: 4px;
}