/* CSS 变量定义 */
:root {
    /* 颜色变量 */
    --color-primary: rgba(157, 182, 140, 1);
    --color-primary-light: rgba(157, 182, 140, 0.6);
    --color-primary-dark: rgba(110, 150, 110, 1);
    --color-secondary: rgba(200, 186, 164, 1);
    --color-dark: rgba(20, 30, 20, 0.85);
    --color-light: rgba(255, 255, 255, 0.9);
    
    /* 动画曲线 */
    --ease-out-cubic: cubic-bezier(0.215, 0.61, 0.355, 1);
    --ease-out-back: cubic-bezier(0.175, 0.885, 0.32, 1.275);
    --ease-in-out-back: cubic-bezier(0.68, -0.55, 0.265, 1.55);
    
    /* 阴影 */
    --shadow-light: 0 10px 25px rgba(0, 0, 0, 0.4);
    --shadow-medium: 0 15px 30px rgba(0, 0, 0, 0.3);
    --shadow-heavy: 0 20px 40px rgba(0, 0, 0, 0.5);
    
    /* 间距 */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 3rem;
    --spacing-xl: 4rem;
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: 'Roboto', 'Noto Serif SC', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f9f9f9;
    overflow-x: hidden;
}

.main-content {
    position: relative;
    z-index: 1;
}

/* 实用类 */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.fade-up {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s var(--ease-out-cubic), transform 0.6s var(--ease-out-cubic);
}

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

/* 响应式容器 */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
}

/* 按钮基础样式 */
.btn {
    display: inline-block;
    padding: 1rem 2rem;
    border: none;
    border-radius: 50px;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.4s var(--ease-out-back);
}

.btn--primary {
    background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 100%);
    color: white;
}

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

/* 响应式断点 */
@media (max-width: 1200px) {
    html { font-size: 15px; }
}

@media (max-width: 992px) {
    html { font-size: 14px; }
}

@media (max-width: 768px) {
    html { font-size: 13px; }
}

@media (max-width: 576px) {
    html { font-size: 12px; }
}