:root{
  --bg:#08080b;--bg-2:#0c0c10;--ink:#f5f5f7;--ink-2:#c9c9d1;--muted:#8b8b96;--muted-2:#6d6d78;
  --stroke:rgba(255,255,255,.10);--stroke-2:rgba(255,255,255,.16);
  --blue:#4da3ff;--ease:cubic-bezier(.22,.61,.36,1);
  color-scheme:dark;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  background:var(--bg);color:var(--ink);
  font:16px/1.7 -apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  -webkit-font-smoothing:antialiased;overflow-x:hidden;
}
body::before{
  content:"";position:fixed;inset:0;pointer-events:none;z-index:0;
  background:
    radial-gradient(900px 600px at 12% -8%,rgba(77,163,255,.10),transparent 60%),
    radial-gradient(700px 500px at 92% 4%,rgba(150,110,255,.09),transparent 62%);
}
.wrap{max-width:1120px;margin:0 auto;padding:0 24px;position:relative;z-index:1}
a{color:inherit;text-decoration:none}

/* nav */
header{position:sticky;top:0;z-index:50;padding:14px 0;background:rgba(8,8,11,.72);backdrop-filter:blur(24px) saturate(180%);border-bottom:1px solid var(--stroke)}
.nav{display:flex;align-items:center;justify-content:space-between;gap:20px}
.brand{display:flex;align-items:center;gap:10px;font-weight:600;letter-spacing:.16em;font-size:13px}
.brand i{width:8px;height:8px;border-radius:50%;background:linear-gradient(135deg,#4da3ff,#a06bff);display:block}
.nav-links{display:flex;gap:26px;font-size:13.5px;color:var(--ink-2)}
.nav-links a:hover{color:#fff}
.btn{
  display:inline-flex;align-items:center;gap:8px;padding:11px 22px;border-radius:999px;font-size:13.5px;
  font-weight:600;border:1px solid var(--stroke-2);transition:.3s var(--ease);
}
.btn:hover{transform:translateY(-1px)}
.btn-primary{background:#f5f5f7;color:#08080b;border-color:transparent}
.btn-ghost{color:var(--ink)}

/* breadcrumb */
.crumb{padding:22px 0 0;font-size:12.5px;color:var(--muted-2)}
.crumb a{color:var(--muted)}
.crumb a:hover{color:var(--ink)}
.crumb span{margin:0 8px;opacity:.5}

/* hero */
.hero{padding:34px 0 10px}
.kicker{font-size:11.5px;letter-spacing:.18em;text-transform:uppercase;color:var(--blue);margin-bottom:16px}
h1{font-size:clamp(30px,4.4vw,50px);line-height:1.1;letter-spacing:-.028em;font-weight:600;max-width:900px}
.meta{display:flex;gap:18px;flex-wrap:wrap;margin-top:20px;font-size:12.5px;color:var(--muted-2)}
.meta b{color:var(--ink-2);font-weight:500}
.lead{margin-top:24px;font-size:17.5px;line-height:1.65;color:var(--ink-2);max-width:760px}

/* hero image */
.hero-img{margin:36px 0 0;border-radius:22px;overflow:hidden;border:1px solid var(--stroke);position:relative}
.hero-img img{width:100%;display:block;aspect-ratio:2.2/1;object-fit:cover}
.hero-img figcaption{padding:12px 18px;font-size:12px;color:var(--muted-2);background:rgba(255,255,255,.02)}

/* toc */
.toc{margin:44px 0;padding:22px 26px;border:1px solid var(--stroke);border-radius:18px;background:rgba(255,255,255,.022)}
.toc h2{font-size:12px;letter-spacing:.16em;text-transform:uppercase;color:var(--muted);margin-bottom:14px;font-weight:600}
.toc ol{list-style:none;counter-reset:t;display:grid;grid-template-columns:repeat(2,1fr);gap:9px 30px}
.toc li{counter-increment:t;font-size:14px;color:var(--ink-2)}
.toc li::before{content:counter(t,decimal-leading-zero) "  ";color:var(--muted-2);font-size:12px;font-variant-numeric:tabular-nums}
.toc a:hover{color:var(--blue)}

/* article */
article{padding:10px 0 60px;max-width:820px}
article h2{font-size:clamp(23px,2.6vw,30px);line-height:1.25;letter-spacing:-.02em;margin:56px 0 18px;font-weight:600;scroll-margin-top:90px}
article h2:first-of-type{margin-top:0}
article h3{font-size:18px;margin:32px 0 12px;font-weight:600;color:var(--ink)}
article p{margin:0 0 18px;color:var(--ink-2)}
article strong{color:#fff;font-weight:600}
article ul,article ol{margin:0 0 20px 22px;color:var(--ink-2)}
article li{margin-bottom:9px}
article a{color:var(--blue);border-bottom:1px solid rgba(77,163,255,.3)}
article a:hover{border-color:var(--blue)}

/* answer box */
.answer{
  margin:0 0 30px;padding:22px 26px;border-radius:18px;
  background:linear-gradient(135deg,rgba(77,163,255,.10),rgba(160,107,255,.06));
  border:1px solid rgba(77,163,255,.22);
}
.answer p{margin:0;color:#e8e8ee;font-size:16px}

/* tables */
.tablewrap{overflow-x:auto;margin:0 0 26px;border:1px solid var(--stroke);border-radius:16px}
table{width:100%;border-collapse:collapse;font-size:14px;min-width:560px}
th{text-align:left;padding:13px 16px;font-size:11px;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);font-weight:600;border-bottom:1px solid var(--stroke-2);background:rgba(255,255,255,.03)}
td{padding:13px 16px;border-bottom:1px solid rgba(255,255,255,.055);color:var(--ink-2);vertical-align:top}
tr:last-child td{border-bottom:none}
td b{color:#fff;font-weight:600}
td.num{font-variant-numeric:tabular-nums;white-space:nowrap}

/* callout */
.callout{
  margin:26px 0;padding:20px 24px;border-left:3px solid var(--blue);border-radius:0 14px 14px 0;
  background:rgba(77,163,255,.06);font-size:14.5px;color:var(--ink-2);
}
.callout b{color:#fff}
.callout.warn{border-left-color:#ffb340;background:rgba(255,179,64,.07)}

/* mistake list */
.mistakes{list-style:none;margin:0 0 26px!important;counter-reset:m}
.mistakes li{
  counter-increment:m;position:relative;padding:16px 0 16px 52px;border-bottom:1px solid rgba(255,255,255,.06);
}
.mistakes li::before{
  content:counter(m,decimal-leading-zero);position:absolute;left:0;top:17px;
  font-size:12px;color:#ff6b6b;font-variant-numeric:tabular-nums;font-weight:600;
}
.mistakes li:last-child{border-bottom:none}
.mistakes b{display:block;color:#fff;margin-bottom:4px;font-size:15px}

/* faq */
.faq{margin:56px 0 0;max-width:820px}
.faq h2{font-size:clamp(23px,2.6vw,30px);letter-spacing:-.02em;margin-bottom:24px}
.faq details{border-bottom:1px solid var(--stroke);padding:20px 0}
.faq summary{
  cursor:pointer;font-size:16px;font-weight:600;color:var(--ink);list-style:none;
  display:flex;justify-content:space-between;gap:16px;align-items:flex-start;
}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"+";color:var(--muted);font-size:20px;line-height:1;flex-shrink:0;transition:transform .3s}
.faq details[open] summary::after{transform:rotate(45deg)}
.faq p{margin:14px 0 0;font-size:15px;color:var(--ink-2)}

/* cta */
.cta{
  margin:70px 0 0;padding:40px;border-radius:24px;border:1px solid var(--stroke-2);
  background:linear-gradient(135deg,rgba(255,255,255,.05),rgba(255,255,255,.02));
  display:flex;align-items:center;justify-content:space-between;gap:30px;flex-wrap:wrap;
}
.cta h2{font-size:26px;letter-spacing:-.02em;margin:0 0 8px;font-weight:600}
.cta p{margin:0;color:var(--muted);font-size:14px}
.cta-actions{display:flex;gap:12px;flex-wrap:wrap}

/* footer */
footer{margin-top:70px;border-top:1px solid var(--stroke);padding:36px 0 44px;font-size:13px;color:var(--muted-2)}
.foot{display:flex;justify-content:space-between;gap:24px;flex-wrap:wrap;align-items:center}
.foot a:hover{color:var(--ink)}
@media(max-width:760px){
  .nav-links{display:none}
  .toc ol{grid-template-columns:1fr}
  .cta{padding:28px}
  .hero-img img{aspect-ratio:1.6/1}
}
/* ---------- shared article extras ---------- */
.answer.two p+p{margin-top:12px}
.grid2{display:grid;grid-template-columns:repeat(2,1fr);gap:18px;margin:0 0 26px}
.card{padding:20px 22px;border:1px solid var(--stroke);border-radius:16px;background:rgba(255,255,255,.022)}
.card h3{font-size:15px;margin:0 0 10px;color:#fff}
.card p{font-size:14px;margin:0;color:var(--ink-2)}
.card .tag{display:inline-block;font-size:10.5px;letter-spacing:.12em;text-transform:uppercase;color:var(--blue);margin-bottom:8px}
.card.bad .tag{color:#ff6b6b}
.card.good .tag{color:#4ade80}
.steps{list-style:none;counter-reset:s;margin:0 0 26px!important}
.steps li{counter-increment:s;position:relative;padding:14px 0 14px 46px;border-bottom:1px solid rgba(255,255,255,.06)}
.steps li:last-child{border-bottom:none}
.steps li::before{content:counter(s);position:absolute;left:0;top:14px;width:26px;height:26px;border-radius:50%;background:rgba(77,163,255,.14);color:var(--blue);font-size:12px;font-weight:700;display:flex;align-items:center;justify-content:center}
.steps b{color:#fff}
figure.inline{margin:28px 0;border-radius:18px;overflow:hidden;border:1px solid var(--stroke)}
figure.inline img{width:100%;display:block;aspect-ratio:2.4/1;object-fit:cover}
figure.inline figcaption{padding:11px 16px;font-size:12px;color:var(--muted-2);background:rgba(255,255,255,.02)}
@media(max-width:760px){.grid2{grid-template-columns:1fr}}