:root{--bg:oklch(96.5% .006 84.6);--surface:oklch(100% 0 0);--fg:oklch(21% .007 78.2);--muted:oklch(47% .018 74);--border:oklch(90.2% .012 79.8);--accent:oklch(58.4% .123 50.7);--accent-ink:oklch(50% .12 50.7);--accent-soft:color-mix(in oklch, var(--accent) 12%, transparent);--fg-soft:color-mix(in oklch, var(--fg) 6%, transparent);--ink-hover:oklch(32% .01 78);--font-display:"Songti SC", "Noto Serif SC", "Source Han Serif SC", "STSong", serif;--font-body:-apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;--font-mono:ui-monospace, "SF Mono", "JetBrains Mono", Menlo, monospace;--fs-h1:clamp(40px, 6.2vw, 84px);--fs-h2:clamp(30px, 3.8vw, 48px);--fs-h3:20px;--fs-lead:clamp(16px, 1.4vw, 19px);--fs-body:16px;--fs-meta:13px;--gap-xs:8px;--gap-sm:12px;--gap-md:20px;--gap-lg:32px;--gap-xl:56px;--gap-2xl:112px;--container:1200px;--gutter:clamp(20px, 4vw, 40px);--radius:999px;--radius-md:14px;--radius-lg:22px}*,:before,:after{box-sizing:border-box}html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}body{background:var(--bg);color:var(--fg);font-family:var(--font-body);font-size:var(--fs-body);-webkit-font-smoothing:antialiased;text-rendering:optimizelegibility;margin:0;line-height:1.7;overflow-x:hidden}img{max-width:100%;height:auto;display:block}a{color:inherit;text-decoration:none}p{text-wrap:pretty;margin:0}h1,h2,h3{text-wrap:balance;margin:0}:focus-visible{outline:2px solid var(--fg);outline-offset:3px;border-radius:6px}.skip{position:absolute;top:8px;left:-9999px}.skip:focus{z-index:100;background:var(--fg);color:var(--bg);border-radius:8px;padding:8px 14px;left:12px}.container{max-width:var(--container);padding-inline:var(--gutter);margin-inline:auto}.section{padding-block:clamp(72px, 10vw, var(--gap-2xl))}.rule{border:0;border-top:1px solid var(--border);margin:0}h1,.h1{font-family:var(--font-display);font-size:var(--fs-h1);letter-spacing:.02em;font-weight:600;line-height:1.12}h2,.h2{font-family:var(--font-display);font-size:var(--fs-h2);letter-spacing:.03em;font-weight:600;line-height:1.22}h3,.h3{font-size:var(--fs-h3);font-weight:600;line-height:1.4}.lead{font-size:var(--fs-lead);color:var(--muted);max-width:34em;line-height:1.8}.eyebrow{font-family:var(--font-body);letter-spacing:.28em;color:var(--accent-ink);margin:0 0 var(--gap-md);font-size:12px;font-weight:600}.eyebrow.plain{color:var(--muted)}.meta{font-size:var(--fs-meta);color:var(--muted)}.num{font-family:var(--font-display);font-variant-numeric:tabular-nums}.topnav{z-index:20;background:color-mix(in oklch, var(--bg) 86%, transparent);-webkit-backdrop-filter:saturate(1.2)blur(14px);border-bottom:1px solid #0000;transition:border-color .2s;position:sticky;top:0}.topnav.scrolled{border-bottom-color:var(--border)}.topnav-inner{justify-content:space-between;align-items:center;gap:var(--gap-md);height:68px;display:flex}.brand{align-items:center;gap:12px;min-height:44px;display:inline-flex}.brand svg{width:29px;height:30px;color:color-mix(in oklch, var(--fg) 75%, var(--bg));flex:none}.brand-zh{font-family:var(--font-display);letter-spacing:.14em;font-size:20px;font-weight:600;line-height:1}.brand-en{letter-spacing:.34em;color:var(--muted);margin-top:4px;font-size:9px;font-weight:600;line-height:1}.topnav nav{align-items:center;gap:4px;display:flex}.topnav nav a{color:var(--muted);border-radius:999px;padding:10px 14px;font-size:14px;transition:background .15s,color .15s}.topnav nav a:hover{color:var(--fg);background:var(--fg-soft)}.topnav nav a[aria-current=page]{color:var(--fg)}@media (width<=760px){.topnav nav .hide-sm{display:none}}.btn{border-radius:var(--radius);letter-spacing:.02em;cursor:pointer;border:1px solid #0000;justify-content:center;align-items:center;gap:10px;min-height:48px;padding:12px 24px;font-size:15px;font-weight:600;transition:background .15s,border-color .15s,transform 50ms;display:inline-flex}.btn:active{transform:translateY(1px)}.btn svg{flex:none;width:18px;height:18px}.btn-primary{background:var(--fg);color:var(--bg);border-color:var(--fg)}.btn-primary:hover{background:var(--ink-hover);border-color:var(--ink-hover);color:var(--bg)}.btn-secondary{color:var(--fg);border-color:color-mix(in oklch, var(--fg) 22%, transparent);background:0 0}.btn-secondary:hover{border-color:var(--fg);background:var(--fg-soft)}.link-arrow{border-bottom:1px solid #0000;align-items:center;gap:6px;min-height:44px;font-size:15px;font-weight:600;display:inline-flex}.link-arrow:after{content:"→";transition:transform .15s}.link-arrow:hover:after{transform:translate(3px)}.link-arrow:hover{border-bottom-color:var(--fg)}.chip{z-index:3;letter-spacing:.08em;background:color-mix(in oklch, var(--surface) 82%, transparent);color:var(--fg);-webkit-backdrop-filter:blur(10px);box-shadow:0 2px 10px color-mix(in oklch, var(--fg) 12%, transparent);pointer-events:none;white-space:nowrap;border-radius:999px;align-items:center;gap:6px;padding:6px 12px;font-size:12px;font-weight:600;display:inline-flex;position:absolute}.chip.dark{background:color-mix(in oklch, var(--fg) 72%, transparent);color:var(--surface)}.chip.tl{top:16px;left:16px}.chip.tr{top:16px;right:16px}.chip.bl{bottom:16px;left:16px}.chip.br{bottom:16px;right:16px}.pagefoot{border-top:1px solid var(--border);padding-block:var(--gap-xl) var(--gap-lg);color:var(--muted);font-size:13px}.foot-grid{gap:var(--gap-lg);grid-template-columns:1.4fr 1fr 1fr 1fr;display:grid}.foot-grid h4{color:var(--fg);letter-spacing:.08em;margin:0 0 12px;font-size:13px;font-weight:600}.foot-grid ul{gap:2px;margin:0;padding:0;list-style:none;display:grid}.foot-grid ul a{padding:6px 0;display:inline-block}.foot-grid ul a:hover{color:var(--fg);text-underline-offset:4px;text-decoration:underline}.foot-legal{margin-top:var(--gap-xl);padding-top:var(--gap-md);border-top:1px solid var(--border);flex-wrap:wrap;justify-content:space-between;gap:8px 24px;display:flex}.foot-legal span,.foot-legal a{white-space:normal}.foot-legal a:hover{color:var(--fg);text-underline-offset:4px;text-decoration:underline}.todo{color:var(--accent-ink)}@media (width<=860px){.foot-grid{grid-template-columns:1fr 1fr}.foot-grid>:first-child{grid-column:1/-1}}