/* ===== 基础样式 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    color: #333;
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ===== 工具类 ===== */
:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --accent-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --dark-color: #1a1a2e;
    --text-color: #333;
    --text-light: #666;
    --text-lighter: #888;
    --bg-light: #f8f9fc;
    --bg-white: #ffffff;
    --shadow-sm: 0 5px 30px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 40px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 20px 50px rgba(102, 126, 234, 0.15);
    --radius-sm: 10px;
    --radius-md: 20px;
    --radius-lg: 30px;
    --transition: all 0.3s ease;
    --transition-slow: all 0.4s ease;
}

.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.8s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

.section-header {
    text-align: center;
    margin-bottom: 70px;
}

.section-header h2 {
    font-size: 2.5rem;
    color: #333;
    margin-bottom: 15px;
}

.section-header p {
    font-size: 1.1rem;
    color: #666;
    max-width: 600px;
    margin: 0 auto;
}