:root {
    /* 背景层 */
    --bg-image: radial-gradient(at 100% 0%, hsla(220, 30%, 90%, 1) 0, transparent 50%), 
                radial-gradient(at 0% 100%, hsla(240, 30%, 95%, 1) 0, transparent 50%),
                linear-gradient(to right, #e2e8f0, #f8fafc);
    --bg-color: #eef2f6;

    /* 扇形卡片层 */
    --card-bg: rgba(255, 255, 255, 0.4);
    --card-border: 1px solid rgba(255, 255, 255, 0.6);
    --card-shadow: 0 20px 50px rgba(0, 0, 0, 0.1);
    --card-title-color: #334155;
    --card-hover-bg: rgba(255, 255, 255, 0.8);
    --card-hover-border: #fff;
    --card-hover-shadow: 0 30px 60px rgba(0, 0, 0, 0.15);

    /* 文字层 */
    --main-title-color: rgba(0,0,0,0.03);
    --sub-title-color: #64748b;
    --text-primary: #1a202c;
    --text-secondary: #94a3b8;

    /* UI 组件 */
    --btn-bg: #0f172a;
    --btn-text: #fff;
    --btn-hover-bg: #1e293b;
    
    /* 阅读器 */
    --reader-bg: #f8fafc;
    --back-btn-bg: white;
    --back-btn-text: #334155;
    
    /* 弹窗 */
    --modal-overlay: rgba(0,0,0,0.4);
    --modal-bg: white;
}

/* --- 全局重置 --- */
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
body {
    /* 背景由 Theme Manager 或各风格独立控制 */
    /* background-color: var(--bg-color); */
    /* background-image: var(--bg-image); */
    height: 100vh; margin: 0; 
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    overflow: hidden;
    color: var(--text-primary);
    
    /* 全局颜色过渡 (纸飞机切换体验优化) */
    transition: background-color 0.5s ease, color 0.5s ease;
}