/* ========== 全局变量定义 ========== */
:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --accent-color: #3b82f6;
    --text-color: #1f2937;
    --text-light: #6b7280;
    --bg-color: #ffffff;
    --bg-light: #f9fafb;
    --bg-dark: #111827;
    --border-color: #e5e7eb;
    --success-color: #10b981;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
}

/* ========== 基础重置 ========== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s ease;
}

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

/* ========== 导航栏 ========== */
.navbar {
    background-color: var(--bg-color);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-menu a {
    color: var(--text-color);
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
}

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

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--primary-color);
}

.menu-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    background: none;
    border: none;
}

.menu-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--text-color);
    margin: 3px 0;
    transition: 0.3s;
}

/* ========== 页面容器 ========== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

section {
    padding: 4rem 0;
}

/* ========== Hero区域 ========== */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 6rem 0;
    text-align: center;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
    font-size: 1rem;
}

.btn-primary {
    background-color: white;
    color: var(--primary-color);
}

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

.btn-secondary {
    background-color: var(--primary-color);
    color: white;
    border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
    background-color: var(--secondary-color);
    border-color: var(--secondary-color);
}

/* ========== 特性卡片 ========== */
.features {
    background-color: var(--bg-light);
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.section-subtitle {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 3rem;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    background-color: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    width: 60px;
    height: 60px;
    background-color: var(--accent-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.feature-card p {
    color: var(--text-light);
    line-height: 1.7;
}

/* ========== CTA区域 ========== */
.cta {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: 5rem 0;
}

.cta h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.cta p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

/* ========== 表单 ========== */
.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-color);
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.3s ease;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

/* ========== 页脚 ========== */
.footer {
    background-color: var(--bg-dark);
    color: white;
    padding: 3rem 0 1.5rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    margin-bottom: 1rem;
    color: white;
}

.footer-section p,
.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 0.5rem;
    display: block;
}

.footer-section a:hover {
    color: var(--accent-color);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

.footer-bottom a {
    color: inherit;
}

.footer-bottom a:hover {
    color: var(--accent-color);
}

/* ========== 响应式设计 ========== */
@media (max-width: 768px) {
    .menu-toggle {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--bg-color);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow-lg);
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

    .section-title {
        font-size: 2rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .cta h2 {
        font-size: 1.75rem;
    }

    .cta p {
        font-size: 1rem;
    }
}

/* ========== 工具类 ========== */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: 1rem; }
.mt-2 { margin-top: 2rem; }
.mt-3 { margin-top: 3rem; }
.mb-1 { margin-bottom: 1rem; }
.mb-2 { margin-bottom: 2rem; }
.mb-3 { margin-bottom: 3rem; }