/* 现代化科技运动风格 - 基础知识 */
:root {
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --secondary-gradient: linear-gradient(135deg, #4e5fc1 0%, #5a6fd8 100%);
  --accent-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --dark-bg: #0f172a;
  --card-bg: rgba(255, 255, 255, 0.05);
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --border-radius: 16px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  --glow: 0 0 20px rgba(102, 126, 234, 0.3);
}

.fundamentals-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.fundamental-chapter {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 2rem;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.fundamental-chapter::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--primary-gradient);
    opacity: 0;
    transition: var(--transition);
    z-index: -1;
}

.fundamental-chapter:hover {
    transform: translateY(-10px) scale(1.02);
    box-shadow: var(--shadow), var(--glow);
    border-color: rgba(102, 126, 234, 0.3);
}

.fundamental-chapter:hover::before {
    opacity: 0.05;
}

.fundamental-chapter h3 {
    color: #667eea;
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
    text-align: center;
    position: relative;
}

.fundamental-chapter h3::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 3px;
    background: var(--primary-gradient);
    border-radius: 2px;
}

.chapter-content {
    margin-top: 1rem;
}

.topic {
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.topic:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.topic h4 {
    color: #667eea;
    margin-bottom: 1rem;
    font-size: 1.2rem;
    position: relative;
}

.topic h4::before {
    content: '';
    position: absolute;
    top: 50%;
    left: -15px;
    transform: translateY(-50%);
    width: 8px;
    height: 8px;
    background: var(--primary-gradient);
    border-radius: 50%;
}

.topic p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.7;
}

.topic .details {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 1rem;
    margin-top: 1rem;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.topic .details h5 {
    color: #667eea;
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

.topic .details ul {
    list-style-type: none;
    padding-left: 0;
}

.topic .details ul li {
    padding: 0.5rem 0;
    position: relative;
    padding-left: 1.5rem;
    transition: var(--transition);
    font-size: 1rem;
}

.topic .details ul li:hover {
    transform: translateX(5px);
}

.topic .details ul li:before {
    content: "•";
    color: #667eea;
    position: absolute;
    left: 0;
    top: 0.5rem;
    font-size: 1.2rem;
}

.intro-text {
    text-align: center;
    font-size: 1.25rem;
    max-width: 800px;
    margin: 0 auto 2rem;
    color: var(--text-secondary);
}

.navigation-buttons {
    display: flex;
    justify-content: space-between;
    margin-top: 2rem;
    gap: 1rem;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .fundamentals-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }
    
    .navigation-buttons {
        flex-direction: column;
        gap: 1rem;
    }
    
    .navigation-buttons a {
        text-align: center;
    }
}