:root{--color-brand:#2563EB;--color-brand-dark:#1D4ED8;--color-brand-light:#DBEAFE;--color-ai:#7C3AED;--color-ai-light:#EDE9FE;--color-success:#059669;--color-warning:#D97706;--color-error:#DC2626;--color-info:#0891B2;--color-title:#111827;--color-text:#374151;--color-muted:#6B7280;--color-placeholder:#9CA3AF;--color-border:#E5E7EB;--color-bg-alt:#F9FAFB;--color-bg:#FFFFFF;--color-footer-bg:#111827;--color-footer-text:#D1D5DB;--color-footer-link:#93C5FD;--font-h1:40px;--font-h2:30px;--font-h3:22px;--font-body:16px;--font-small:14px;--font-tiny:12px;--lh-heading:1.3;--lh-body:1.75;--lh-small:1.6;--space-xs:4px;--space-sm:8px;--space-md:16px;--space-lg:24px;--space-xl:32px;--space-2xl:48px;--space-3xl:64px;--space-4xl:96px;--radius-sm:4px;--radius-md:8px;--radius-lg:12px;--radius-full:9999px;--shadow-sm:0 1px 2px rgba(0,0,0,0.05);--shadow-md:0 4px 6px rgba(0,0,0,0.07);--shadow-lg:0 10px 15px rgba(0,0,0,0.1);--transition-fast:0.15s ease;--transition-normal:0.2s ease;--transition-slow:0.3s ease-in-out;--max-width:1200px;--max-width-reading:720px;--nav-height:64px;--nav-height-mobile:56px;--font-sans:"PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei", sans-serif;--font-display:"Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif}