:root{
  --ink:#101D2D; --ink-2:#3C4B5D; --ink-3:#6B7B8D; --line:#E3EAF1; --line-2:#CFE0EC;
  --bg:#FFFFFF; --bg-soft:#F5F9FC; --accent:#0288D1; --accent-dk:#0874B2; --accent-bg:#E6F3FB;
  --ok:#12A36A; --ok-bg:#E8F8F1; --warn:#B26A00; --warn-bg:#FFF4E0; --bad:#C23B4B; --bad-bg:#FDECEE;
  --r-sm:10px; --r:14px; --r-lg:20px;
  --shadow:0 1px 2px rgba(16,29,45,.04),0 8px 24px rgba(16,29,45,.06);
  --font:"Google Sans","Plus Jakarta Sans",system-ui,-apple-system,"Segoe UI",sans-serif;
  --mono:"JetBrains Mono",ui-monospace,Consolas,monospace;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:88px}
body{margin:0;font-family:var(--font);color:var(--ink);background:var(--bg);font-size:17px;line-height:1.65;-webkit-font-smoothing:antialiased}
a{color:var(--accent);text-decoration:none}
a:hover{color:var(--accent-dk);text-decoration:underline}
:focus-visible{outline:3px solid rgba(2,136,209,.45);outline-offset:2px;border-radius:6px}
code{font-family:var(--mono);font-size:.86em;background:var(--bg-soft);border:1px solid var(--line);padding:.1em .4em;border-radius:6px}

/* header */
.top{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.86);backdrop-filter:saturate(1.4) blur(12px);border-bottom:1px solid var(--line)}
.top-in{max-width:1240px;margin:0 auto;padding:0 20px;height:64px;display:flex;align-items:center;gap:28px}
.logo{font-weight:800;font-size:19px;color:var(--ink);letter-spacing:-.01em}
.logo b{color:var(--accent)}
.logo:hover{text-decoration:none;color:var(--ink)}
.nav{display:flex;gap:22px;font-size:15px;font-weight:500}
.nav a{color:var(--ink-2)}
.nav a.on{color:var(--accent)}
.top .btn{margin-left:auto}
.btn{display:inline-flex;align-items:center;gap:8px;background:var(--accent);color:#fff;font-weight:600;font-size:15px;padding:11px 18px;border-radius:var(--r-sm);border:0;cursor:pointer;transition:background .15s}
.btn:hover{background:var(--accent-dk);color:#fff;text-decoration:none}
.btn.ghost{background:#fff;color:var(--ink);border:1px solid var(--line-2)}
.btn.ghost:hover{background:var(--bg-soft);color:var(--ink)}
@media (max-width:820px){.nav{display:none}}

/* hero */
.hero{position:relative;overflow:hidden;border-bottom:1px solid var(--line)}
.hero::before{content:"";position:absolute;inset:-40% -10% auto auto;width:720px;height:720px;background:radial-gradient(closest-side,rgba(2,136,209,.10),transparent);pointer-events:none}
.hero::after{content:"";position:absolute;inset:auto auto -60% -15%;width:640px;height:640px;background:radial-gradient(closest-side,rgba(18,163,106,.07),transparent);pointer-events:none}
.hero-in{position:relative;max-width:1240px;margin:0 auto;padding:36px 20px 40px}
.crumbs{font-size:14px;color:var(--ink-3);display:flex;flex-wrap:wrap;gap:6px}
.crumbs a{color:var(--ink-3)}
.crumbs span[aria-hidden]{opacity:.5}
.pills{display:flex;flex-wrap:wrap;gap:8px;margin:18px 0 14px}
.pill{display:inline-flex;align-items:center;gap:6px;font-size:12.5px;font-weight:600;letter-spacing:.02em;padding:5px 11px;border-radius:999px;background:var(--accent-bg);color:var(--accent-dk)}
.pill.ok{background:var(--ok-bg);color:#0C7A4F}
.pill.mute{background:var(--bg-soft);color:var(--ink-2);border:1px solid var(--line)}
h1{font-size:clamp(30px,4.2vw,46px);line-height:1.12;letter-spacing:-.02em;margin:0;max-width:900px;font-weight:800}
h1 em{font-style:normal;color:var(--accent)}
.lede{font-size:19px;color:var(--ink-2);max-width:760px;margin:16px 0 0}
.meta{display:flex;flex-wrap:wrap;gap:18px;margin-top:20px;font-size:14px;color:var(--ink-3)}
.meta strong{color:var(--ink-2);font-weight:600}

/* layout */
.wrap{max-width:1240px;margin:0 auto;padding:40px 20px 80px;display:grid;grid-template-columns:260px minmax(0,1fr);gap:56px}
@media (max-width:1000px){.wrap{grid-template-columns:1fr;gap:0}.side{display:none}}
.side{position:sticky;top:88px;align-self:start;max-height:calc(100vh - 110px);overflow:auto;font-size:14.5px}
.side h4{font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--ink-3);margin:0 0 10px}
.toc{list-style:none;margin:0 0 28px;padding:0;border-left:2px solid var(--line)}
.toc a{display:block;padding:5px 0 5px 14px;margin-left:-2px;border-left:2px solid transparent;color:var(--ink-2);line-height:1.4}
.toc a:hover{color:var(--accent);text-decoration:none}
.toc a.on{color:var(--accent);border-left-color:var(--accent);font-weight:600}
.course{background:var(--bg-soft);border:1px solid var(--line);border-radius:var(--r);padding:16px}
.course .bar{height:6px;background:var(--line);border-radius:6px;overflow:hidden;margin:8px 0 14px}
.course .bar i{display:block;height:100%;width:17%;background:var(--accent)}
.course ol{margin:0;padding:0;list-style:none;counter-reset:l}
.course li{counter-increment:l;display:flex;gap:10px;padding:5px 0;color:var(--ink-3);line-height:1.35}
.course li::before{content:counter(l);flex:none;width:20px;height:20px;border-radius:50%;background:#fff;border:1px solid var(--line-2);font-size:11px;display:grid;place-items:center;color:var(--ink-3)}
.course li.done::before{content:"✓";background:var(--ok);border-color:var(--ok);color:#fff}
.course li.cur{color:var(--ink);font-weight:600}
.course li.cur::before{background:var(--accent);border-color:var(--accent);color:#fff}

/* article */
article{max-width:780px;min-width:0}
article h2{font-size:28px;line-height:1.25;letter-spacing:-.015em;margin:56px 0 14px;font-weight:800}
article h3{font-size:20px;line-height:1.35;margin:30px 0 8px;font-weight:700}
article p{margin:0 0 16px;color:var(--ink-2)}
article li{color:var(--ink-2);margin-bottom:8px}
article strong{color:var(--ink)}
.num{counter-reset:s;list-style:none;padding:0}
.num>li{counter-increment:s;position:relative;padding-left:44px;margin-bottom:16px}
.num>li::before{content:counter(s);position:absolute;left:0;top:1px;width:28px;height:28px;border-radius:8px;background:var(--accent-bg);color:var(--accent-dk);font-weight:700;font-size:14px;display:grid;place-items:center}

.short{background:linear-gradient(135deg,#F2F9FE,#fff 70%);border:1px solid var(--line-2);border-radius:var(--r-lg);padding:22px 24px;margin:0 0 8px}
.short h2{margin:0 0 8px;font-size:15px;letter-spacing:.08em;text-transform:uppercase;color:var(--accent-dk)}
.short p{margin:0;color:var(--ink);font-size:17.5px}

.quote{border-left:4px solid var(--accent);background:var(--bg-soft);border-radius:0 var(--r) var(--r) 0;padding:14px 18px;margin:0 0 14px}
.quote p{margin:0;color:var(--ink)}
.quote cite{display:block;margin-top:6px;font-style:normal;font-size:13.5px;color:var(--ink-3)}

.cause{border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;margin:0 0 12px;background:#fff}
.cause h3{margin:0 0 6px;font-size:17.5px;display:flex;align-items:center;gap:10px}
.cause p{margin:0;font-size:16px}
.tag{font-size:11.5px;font-weight:700;letter-spacing:.04em;padding:3px 8px;border-radius:999px;white-space:nowrap}
.tag.d{background:var(--warn-bg);color:var(--warn)}
.tag.c{background:var(--bad-bg);color:var(--bad)}

/* figures */
figure{margin:28px 0 30px;background:#fff;border:1px solid var(--line);border-radius:var(--r-lg);box-shadow:var(--shadow);overflow:hidden}
figure .fig-head{display:flex;align-items:center;gap:10px;padding:14px 18px;border-bottom:1px solid var(--line);font-size:13px;font-weight:700;letter-spacing:.05em;text-transform:uppercase;color:var(--ink-3)}
figure .fig-body{padding:18px}
figure .scroll{overflow-x:auto}
figure svg{display:block;width:100%;height:auto}
figcaption{padding:12px 18px 16px;font-size:14.5px;color:var(--ink-3);border-top:1px solid var(--line);background:var(--bg-soft)}
.fig-tree svg{min-width:720px}
.fig-flow svg{min-width:640px}

table{width:100%;border-collapse:collapse;font-size:15px}
th,td{text-align:left;vertical-align:top;padding:12px 14px;border-bottom:1px solid var(--line)}
thead th{font-size:13px;letter-spacing:.04em;text-transform:uppercase;color:var(--ink-3);background:var(--bg-soft)}
tbody th{color:var(--ink);font-weight:600;width:24%}
td{color:var(--ink-2)}
.cmp td:nth-child(2){background:rgba(255,244,224,.35)}
.cmp td:nth-child(3){background:rgba(253,236,238,.35)}

/* GSC mock */
.gsc{font-family:Roboto,Arial,sans-serif;font-size:14px;color:#202124;border:1px solid #DADCE0;border-radius:8px;overflow:hidden;min-width:620px}
.gsc-h{padding:14px 16px;font-size:16px;border-bottom:1px solid #DADCE0;display:flex;justify-content:space-between;align-items:center}
.gsc-h small{color:#5F6368;font-size:12px}
.gsc table{font-size:13.5px}
.gsc th{font-size:12px;text-transform:none;letter-spacing:0;color:#5F6368;background:#fff;font-weight:500}
.gsc td,.gsc th{padding:10px 14px;border-bottom:1px solid #EEF0F2;color:#202124}
.gsc tr.hl td{background:#FFF8E6}
.gsc .n{text-align:right;font-variant-numeric:tabular-nums}
.gsc .spark{display:inline-block;width:70px;height:16px;vertical-align:middle}
.mark{display:inline-grid;place-items:center;width:22px;height:22px;border-radius:50%;background:var(--accent);color:#fff;font:700 12px/1 var(--font);margin-left:6px;vertical-align:middle}
.legend{list-style:none;padding:0;margin:16px 0 0;font-size:15px}
.legend li{display:flex;gap:10px;margin-bottom:8px;color:var(--ink-2)}
.legend .mark{flex:none;margin:2px 0 0}

/* callouts */
.note{display:flex;gap:14px;border-radius:var(--r);padding:16px 18px;margin:20px 0;font-size:16px}
.note svg{flex:none;width:22px;height:22px;margin-top:2px}
.note p{margin:0;color:var(--ink)}
.note.info{background:var(--accent-bg)} .note.info svg{color:var(--accent)}
.note.warn{background:var(--warn-bg)} .note.warn svg{color:var(--warn)}

.myths{list-style:none;padding:0}
.myths li{display:grid;grid-template-columns:auto 1fr;gap:4px 12px;border:1px solid var(--line);border-radius:var(--r);padding:14px 16px;margin-bottom:10px}
.myths .x{grid-row:span 2;width:26px;height:26px;border-radius:8px;background:var(--bad-bg);color:var(--bad);display:grid;place-items:center;font-weight:800}
.myths b{color:var(--ink)}

.ok-list{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:10px;padding:0;list-style:none}
.ok-list li{background:var(--ok-bg);border-radius:var(--r);padding:14px 16px;margin:0;font-size:15.5px}
.ok-list b{display:block;color:#0C7A4F;margin-bottom:2px}

/* CTA */
.cta{position:relative;overflow:hidden;border-radius:var(--r-lg);padding:28px;background:var(--ink);color:#fff;margin:40px 0}
.cta::after{content:"";position:absolute;right:-120px;top:-120px;width:360px;height:360px;background:radial-gradient(closest-side,rgba(2,136,209,.55),transparent)}
.cta>*{position:relative}
.cta h2{color:#fff;margin:0 0 8px;font-size:24px}
.cta p{color:#C9D6E3;margin:0 0 18px}
.cta form{display:flex;gap:10px;flex-wrap:wrap}
.cta input{flex:1 1 240px;min-width:0;font:inherit;font-size:16px;padding:12px 14px;border-radius:var(--r-sm);border:1px solid #33465C;background:#16273B;color:#fff}
.cta input::placeholder{color:#8DA1B5}
.cta .chk{display:flex;flex-wrap:wrap;gap:14px;margin-top:14px;font-size:13.5px;color:#9FB3C7}
.cta .chk span::before{content:"✓ ";color:#3FD49A}

details{border:1px solid var(--line);border-radius:var(--r);margin-bottom:10px;background:#fff}
summary{cursor:pointer;list-style:none;padding:15px 48px 15px 18px;font-weight:600;position:relative}
summary::-webkit-details-marker{display:none}
summary::after{content:"";position:absolute;right:18px;top:50%;width:9px;height:9px;border-right:2px solid var(--ink-3);border-bottom:2px solid var(--ink-3);transform:translateY(-70%) rotate(45deg);transition:transform .2s}
details[open] summary::after{transform:translateY(-30%) rotate(-135deg)}
details p{padding:0 18px 16px;margin:0}

.sources{font-size:15px}
.sources li{margin-bottom:6px}
.next{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:40px}
.next a{border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;color:var(--ink)}
.next a:hover{border-color:var(--accent);text-decoration:none}
.next small{display:block;color:var(--ink-3);font-size:13px}
.next a:last-child,.next span:last-child{text-align:right}
.next .soon{border:1px dashed var(--line-2);border-radius:var(--r);padding:16px 18px;color:var(--ink-3)}
.next .soon small{display:block;font-size:13px}
@media (max-width:600px){.next{grid-template-columns:1fr}.next a:last-child{text-align:left}}
footer{border-top:1px solid var(--line);color:var(--ink-3);font-size:14px}
footer div{max-width:1240px;margin:0 auto;padding:24px 20px;display:flex;flex-wrap:wrap;gap:16px;justify-content:space-between}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{transition:none!important}}

/* code blocks and comparisons */
pre{background:#0F1B2A;color:#E3EAF1;border-radius:12px;padding:16px 18px;overflow-x:auto;font-family:var(--mono);font-size:14px;line-height:1.65;margin:0 0 18px}
pre code{background:none;border:0;padding:0;color:inherit;font-size:inherit}
figure pre{margin:0;border-radius:0}
.t-tag{color:#7CC7F0}.t-attr{color:#F5C26B}.t-str{color:#8FE3B5}.t-com{color:#7D8EA3}.t-bad{background:rgba(194,59,75,.45);border-radius:4px;padding:0 2px}.t-good{background:rgba(18,163,106,.35);border-radius:4px;padding:0 2px}
.code-cmp{display:grid;grid-template-columns:1fr 1fr}
.code-cmp>div{min-width:0;border-right:1px solid #22344A}
.code-cmp>div:last-child{border-right:0}
.code-cmp h4{margin:0;padding:10px 18px;font-size:12.5px;letter-spacing:.06em;text-transform:uppercase;background:#16273B}
.code-cmp .bad h4{color:#F59AA5}.code-cmp .good h4{color:#7FE0B0}
.code-cmp ul{margin:0;padding:12px 18px 16px 34px;background:#0F1B2A;color:#C9D6E3;font-size:14px}
.code-cmp li{color:#C9D6E3;margin-bottom:4px}
@media (max-width:720px){.code-cmp{grid-template-columns:1fr}.code-cmp>div{border-right:0;border-bottom:1px solid #22344A}}
.fig-dark{background:#0F1B2A;border-color:#22344A}
.fig-dark .fig-head{color:#9FB3C7;border-color:#22344A}
.fig-dark figcaption{background:#16273B;color:#9FB3C7;border-color:#22344A}
.rules{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:10px;padding:18px}
.rules div{border:1px solid var(--line);border-radius:12px;padding:12px 14px;background:#fff}
.rules code{font-weight:600;color:var(--accent-dk);background:var(--accent-bg);border-color:transparent}
.rules p{margin:6px 0 0;font-size:14.5px}
.ok-bad{display:grid;grid-template-columns:1fr 1fr;gap:0}
.ok-bad>div{padding:18px}
.ok-bad>div:first-child{background:#F3FBF7;border-right:1px solid var(--line)}
.ok-bad>div:last-child{background:#FEF6F7}
.ok-bad h4{margin:0 0 10px;font-size:13px;letter-spacing:.06em;text-transform:uppercase}
.ok-bad>div:first-child h4{color:#0C7A4F}.ok-bad>div:last-child h4{color:var(--bad)}
.ok-bad ul{margin:0;padding-left:18px;font-size:15px}
.ok-bad li{margin-bottom:6px}
@media (max-width:640px){.ok-bad{grid-template-columns:1fr}.ok-bad>div:first-child{border-right:0;border-bottom:1px solid var(--line)}}
.fig-dark code{background:#22344A;border-color:#33465C;color:#E3EAF1}
.scroll{overflow-x:auto;max-width:100%}
article :not(pre)>code{overflow-wrap:anywhere}
/* v2: figures use the full column, text stays at reading width */
article{max-width:none}
article>*:not(figure):not(.cta):not(.scroll){max-width:780px}
figure .fig-body{padding:14px}

/* v3: author byline box */
.author-box{display:flex;gap:16px;align-items:flex-start;border:1px solid var(--line-2);border-radius:var(--r-lg);padding:20px 22px;margin:44px 0 0;background:linear-gradient(160deg,#F2F9FE,#fff 65%);max-width:780px}
.author-ini{flex:none;width:52px;height:52px;border-radius:50%;background:var(--accent);color:#fff;font-weight:800;display:grid;place-items:center;font-size:17px}
.author-k{font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--ink-3);font-weight:700}
.author-n{font-size:18px;font-weight:800;color:var(--ink)}
.author-r{font-size:14px;color:var(--accent-dk);font-weight:600;margin-bottom:6px}
.author-box p{margin:0;font-size:15px;color:var(--ink-2)}
.hub-author{margin-top:14px;font-size:14.5px;color:var(--ink-3)}
.hub-author a{font-weight:600}
.author-img{flex:none;width:64px;height:64px;border-radius:50%;object-fit:cover;display:block}