/* =====================================================================
   SenderReputation.org - Guide "Documentation" design system
   Namespaced under .gd. Loaded on /guides/* only.
   Wide content + right rail (no left TOC), premium prose components,
   diagrams, callouts, steps, facts, comparison tables, FAQ Q-cards,
   a premium "Continue learning" section, and an eye-catching keyworded
   CTA pinned to the bottom of the related-tools rail.
   ===================================================================== */
.gd{
  --ink:#0B1220;--ink-2:#1E293B;--body:#334155;--body-2:#475569;--muted:#64748B;--muted-2:#94A3B8;
  --line:#E6EBF1;--line-2:#F1F5F9;--surface-2:#F8FAFC;--surface-3:#FCFCFD;
  --sky:#0EA5E9;--sky-deep:#0369A1;--sky-600:#0284C7;--sky-400:#38BDF8;--sky-bg:#F0F9FF;--sky-border:#BAE6FD;
  --success:#10B981;--success-deep:#047857;--success-bg:#ECFDF5;--success-border:#A7F3D0;
  --warn:#F59E0B;--warn-deep:#B45309;--warn-bg:#FFFBEB;--warn-border:#FDE68A;
  --danger:#EF4444;--danger-deep:#B91C1C;--danger-bg:#FEF2F2;--danger-border:#FECACA;
  --card:0 1px 2px rgba(15,23,42,.04),0 18px 40px -24px rgba(15,23,42,.22);
  color:var(--body);
}
.gd svg{display:block}
.gd .grad{background:linear-gradient(108deg,var(--sky),var(--sky-deep));-webkit-background-clip:text;background-clip:text;color:transparent}
.gd .mono{font-family:'JetBrains Mono',monospace}

/* Reading progress bar */
.gd-progress{position:fixed;top:0;left:0;height:3px;width:0;z-index:60;background:linear-gradient(90deg,var(--sky),var(--sky-400));box-shadow:0 0 10px rgba(14,165,233,.6);transition:width .1s linear}

/* ── Hero ── */
.gd-hero{position:relative;background:#fff;border-bottom:1px solid var(--line);padding:2.6rem 0 2.4rem;overflow:hidden}
.gd-hero::before{content:'';position:absolute;inset:0;
  background-image:radial-gradient(circle at 82% 0%,rgba(186,230,253,.34),transparent 46%),radial-gradient(circle at 14% 30%,rgba(186,230,253,.22),transparent 56%),radial-gradient(#CBD5E1 1px,transparent 1px);
  background-size:auto,auto,24px 24px;
  -webkit-mask-image:radial-gradient(ellipse 86% 76% at 42% 24%,#000 32%,transparent 82%);mask-image:radial-gradient(ellipse 86% 76% at 42% 24%,#000 32%,transparent 82%);opacity:.6;pointer-events:none}
.gd-hero .container{position:relative;z-index:1}
.gd .breadcrumbs{padding:0;font-size:.82rem}
.gd .breadcrumbs ol{display:flex;align-items:center;flex-wrap:wrap;gap:6px;margin:0;padding:0;list-style:none}
.gd .breadcrumbs a{color:var(--muted);font-weight:500;min-height:0}
.gd .breadcrumbs a:hover{color:var(--sky-deep)}
.gd .breadcrumbs .separator{color:var(--muted-2);font-size:.75rem}
.gd .breadcrumbs .current{color:var(--body-2);font-weight:600}
.gd-pills{display:flex;align-items:center;gap:9px;flex-wrap:wrap;margin:1.1rem 0 .9rem}
.gd-level{display:inline-flex;align-items:center;gap:7px;font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.06em;padding:5px 12px;border-radius:999px;background:var(--sky-bg);border:1px solid var(--sky-border);color:var(--sky-deep)}
.gd-level.beginner{background:var(--success-bg);border-color:var(--success-border);color:var(--success-deep)}
.gd-level.intermediate{background:var(--sky-bg);border-color:var(--sky-border);color:var(--sky-deep)}
.gd-level.advanced{background:var(--warn-bg);border-color:var(--warn-border);color:var(--warn-deep)}
.gd-hero h1{font-size:clamp(2.1rem,4.4vw,3rem);line-height:1.06;letter-spacing:-.03em;color:var(--ink);font-weight:800;max-width:20ch;text-wrap:balance}
.gd-lead{font-size:clamp(1.08rem,2vw,1.24rem);line-height:1.6;color:var(--body-2);max-width:62ch;margin-top:.9rem;text-wrap:pretty}
.gd-meta{display:flex;align-items:center;gap:14px;flex-wrap:wrap;margin-top:1.4rem;font-size:.84rem;color:var(--muted)}
.gd-meta .m{display:inline-flex;align-items:center;gap:7px}
.gd-meta .m svg{color:var(--sky-deep)}
.gd-meta .dot{width:3px;height:3px;border-radius:50%;background:var(--muted-2)}

/* ── Body layout: wide content + right rail ── */
.gd-body{padding:2.6rem 0 1rem;background:#fff}
.gd-grid{display:grid;grid-template-columns:minmax(0,1fr) 304px;gap:48px;align-items:start}
@media (max-width:1000px){.gd-grid{grid-template-columns:1fr;gap:34px}}
.gd-article{min-width:0;max-width:none}

/* Prose */
.gd-article>h2{font-size:clamp(1.55rem,2.8vw,1.95rem);letter-spacing:-.02em;color:var(--ink);font-weight:800;line-height:1.2;margin:2.6rem 0 .9rem;scroll-margin-top:80px;text-wrap:balance}
.gd-article>h2:first-child{margin-top:0}
.gd-article h3{font-size:1.24rem;letter-spacing:-.01em;color:var(--ink);font-weight:700;margin:1.9rem 0 .7rem;text-wrap:balance}
.gd-article p{font-size:1.06rem;line-height:1.78;color:var(--body);margin-bottom:1.15rem;text-wrap:pretty}
.gd-article .lead-answer{font-size:1.12rem;line-height:1.7;color:var(--ink-2);font-weight:500;border-left:3px solid var(--sky);padding-left:18px;margin:0 0 1.3rem}
.gd-article a{color:var(--sky-deep);text-decoration:underline;text-decoration-color:var(--sky-border);text-underline-offset:2px}
.gd-article a:hover{text-decoration-color:var(--sky)}
.gd-article strong{color:var(--ink);font-weight:700}
.gd-article code{font-family:'JetBrains Mono',monospace;font-size:.86em;background:var(--sky-bg);color:var(--sky-deep);border:1px solid var(--sky-border);padding:1px 6px;border-radius:6px;white-space:nowrap}
.gd-article ul,.gd-article ol{margin:0 0 1.3rem;padding-left:0;list-style:none;display:grid;gap:9px}
.gd-article ul li{position:relative;padding-left:30px;font-size:1.04rem;line-height:1.65;color:var(--body)}
.gd-article ul li::before{content:'';position:absolute;left:8px;top:.62em;width:8px;height:8px;border-radius:2px;background:var(--sky);transform:rotate(45deg)}
.gd-article ol{counter-reset:li}
.gd-article ol li{counter-increment:li;position:relative;padding-left:38px;font-size:1.04rem;line-height:1.65;color:var(--body)}
.gd-article ol li::before{content:counter(li);position:absolute;left:0;top:.05em;width:24px;height:24px;border-radius:7px;background:var(--sky-bg);border:1px solid var(--sky-border);color:var(--sky-deep);font-family:'JetBrains Mono',monospace;font-size:.78rem;font-weight:700;display:flex;align-items:center;justify-content:center}

/* Callouts (key takeaway / tip / warning) */
.gd-callout{display:flex;gap:14px;align-items:flex-start;margin:1.7rem 0;padding:17px 19px;border-radius:14px;border:1px solid var(--sky-border);background:linear-gradient(180deg,var(--sky-bg),#fff)}
.gd-callout .ic{flex-shrink:0;width:30px;height:30px;border-radius:9px;display:flex;align-items:center;justify-content:center;color:#fff;background:linear-gradient(140deg,var(--sky),var(--sky-600))}
.gd-callout .cb{min-width:0}
.gd-callout .cb strong{display:block;font-size:.78rem;text-transform:uppercase;letter-spacing:.06em;color:var(--sky-deep);margin-bottom:3px}
.gd-callout .cb p{margin:0;font-size:.98rem;line-height:1.6;color:var(--body)}
.gd-callout.tip{border-color:var(--success-border);background:linear-gradient(180deg,var(--success-bg),#fff)}
.gd-callout.tip .ic{background:linear-gradient(140deg,#34D399,var(--success-deep))}
.gd-callout.tip .cb strong{color:var(--success-deep)}
.gd-callout.warn{border-color:var(--warn-border);background:linear-gradient(180deg,var(--warn-bg),#fff)}
.gd-callout.warn .ic{background:linear-gradient(140deg,#FBBF24,var(--warn-deep))}
.gd-callout.warn .cb strong{color:var(--warn-deep)}

/* Step cards (richer than ol) */
.gd-steps{display:grid;gap:12px;margin:1.5rem 0;counter-reset:st}
.gd-step{counter-increment:st;position:relative;display:grid;grid-template-columns:auto 1fr;gap:16px;align-items:start;padding:18px 20px;border:1px solid var(--line);border-radius:14px;background:#fff;box-shadow:var(--card)}
.gd-step .num{width:34px;height:34px;border-radius:10px;display:flex;align-items:center;justify-content:center;font-family:'JetBrains Mono',monospace;font-weight:700;color:#fff;background:linear-gradient(140deg,var(--sky),var(--sky-600));box-shadow:0 8px 16px -8px rgba(2,132,199,.6)}
.gd-step .num::before{content:counter(st,decimal-leading-zero)}
.gd-step h4{font-size:1.06rem;color:var(--ink);font-weight:700;margin-bottom:4px}
.gd-step p{margin:0;font-size:.98rem;line-height:1.6;color:var(--body-2)}
.gd-step p code{font-size:.85em}

/* Fact / stat strip */
.gd-facts{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px;margin:1.7rem 0;padding:0}
.gd-fact{border:1px solid var(--line);border-radius:14px;background:linear-gradient(180deg,var(--surface-2),#fff);padding:18px;text-align:center;box-shadow:var(--card)}
.gd-fact .n{font-family:'JetBrains Mono',monospace;font-weight:700;font-size:1.7rem;letter-spacing:-.02em;background:linear-gradient(120deg,var(--sky),var(--sky-deep));-webkit-background-clip:text;background-clip:text;color:transparent;line-height:1}
.gd-fact .l{font-size:.84rem;color:var(--muted);margin-top:7px;line-height:1.4}

/* Comparison / data table */
.gd-table-wrap{margin:1.6rem 0;border:1px solid var(--line);border-radius:14px;overflow:hidden;box-shadow:var(--card)}
.gd-table{width:100%;border-collapse:collapse;font-size:.96rem}
.gd-table thead th{text-align:left;font-size:.78rem;font-weight:700;text-transform:uppercase;letter-spacing:.04em;color:var(--muted);padding:13px 18px;background:var(--surface-2);border-bottom:1px solid var(--line)}
.gd-table tbody td,.gd-table tbody th{padding:14px 18px;border-bottom:1px solid var(--line-2);vertical-align:top;color:var(--body);line-height:1.55;text-align:left}
.gd-table tbody tr:last-child td,.gd-table tbody tr:last-child th{border-bottom:none}
.gd-table tbody th{font-weight:600;color:var(--ink-2);white-space:nowrap}
.gd-table tbody tr:hover{background:var(--surface-3)}
.gd-table code{font-family:'JetBrains Mono',monospace;font-size:.88em;color:var(--sky-deep)}
.gd-table .yes{color:var(--success-deep);font-weight:600}
.gd-table .no{color:var(--danger-deep);font-weight:600}

/* Diagram block (visual flows) */
.gd-diagram{margin:1.8rem 0;border:1px solid var(--line);border-radius:16px;background:radial-gradient(circle at 50% 0%,var(--sky-bg),transparent 64%),#FCFEFF;padding:24px 22px;box-shadow:var(--card)}
.gd-diagram-cap{display:flex;align-items:center;gap:8px;font-size:.74rem;font-weight:700;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);margin-bottom:18px}
.gd-diagram-cap svg{color:var(--sky)}
.gd-flow{display:flex;align-items:stretch;justify-content:center;gap:0;flex-wrap:wrap}
.gd-node{flex:1;min-width:140px;max-width:230px;text-align:center;padding:16px 14px;border:1.5px solid var(--sky-border);border-radius:13px;background:#fff;box-shadow:0 6px 16px -10px rgba(15,23,42,.2)}
.gd-node .ni{width:38px;height:38px;border-radius:11px;margin:0 auto 10px;display:flex;align-items:center;justify-content:center;color:#fff;background:linear-gradient(140deg,var(--sky),var(--sky-600))}
.gd-node h5{font-size:.95rem;color:var(--ink);font-weight:700;margin-bottom:3px}
.gd-node p{font-size:.82rem;color:var(--muted);line-height:1.45;margin:0}
.gd-node.good{border-color:var(--success-border)}.gd-node.good .ni{background:linear-gradient(140deg,#34D399,var(--success-deep))}
.gd-node.bad{border-color:var(--danger-border)}.gd-node.bad .ni{background:linear-gradient(140deg,#F87171,var(--danger-deep))}
.gd-arrow{display:flex;align-items:center;justify-content:center;color:var(--sky);padding:0 6px}
@media (max-width:620px){.gd-flow{flex-direction:column}.gd-arrow{transform:rotate(90deg);padding:6px 0}}

/* Pull quote */
.gd-quote{margin:1.8rem 0;padding:6px 0 6px 24px;border-left:4px solid var(--sky);font-size:1.24rem;line-height:1.5;font-weight:600;color:var(--ink-2);letter-spacing:-.01em}

/* Guide nav (prev/next) */
.gd-nav{display:flex;align-items:center;justify-content:space-between;gap:14px;flex-wrap:wrap;margin-top:2.4rem;padding-top:1.6rem;border-top:1px solid var(--line)}
.gd-nav a{display:inline-flex;align-items:center;gap:8px;font-weight:600;font-size:.92rem;padding:11px 18px;border-radius:11px;border:1px solid var(--line);color:var(--ink-2);background:#fff;transition:border-color .15s,background .15s,color .15s}
.gd-nav a:hover{border-color:var(--sky-border);background:var(--sky-bg);color:var(--sky-deep)}
.gd-nav a.next{color:#fff;background:linear-gradient(135deg,var(--sky),var(--sky-600));border-color:transparent;box-shadow:0 10px 22px -10px rgba(2,132,199,.6)}
.gd-nav a.next:hover{color:#fff}

/* Reviewer credit (matches the glossary/bounce "Reviewed by ..." line) */
.gd-reviewer{display:flex;align-items:center;gap:8px;margin-top:2rem;padding-top:1.5rem;border-top:1px solid var(--line);font-size:.86rem;color:var(--muted);font-weight:500}
.gd-reviewer svg{color:var(--success);flex-shrink:0}

/* ── Right rail ── */
.gd-rail{position:sticky;top:84px;display:grid;gap:16px;align-self:start;height:fit-content}
@media (max-width:1000px){.gd-rail{position:static}}
.gd-rail-card{border:1px solid var(--line);border-radius:16px;background:#fff;box-shadow:var(--card);overflow:hidden}
.gd-rail-card h3{font-size:.72rem;text-transform:uppercase;letter-spacing:.07em;color:var(--muted-2);font-weight:700;padding:15px 17px 0}
.gd-rail-links{padding:8px 9px 10px}
.gd-rail-link{display:flex;align-items:center;gap:11px;padding:10px 8px;border-radius:11px;text-decoration:none;transition:background .15s}
.gd-rail-link:hover{background:var(--surface-2)}
.gd-rail-link .ic{flex-shrink:0;width:34px;height:34px;border-radius:10px;display:flex;align-items:center;justify-content:center;background:var(--sky-bg);color:var(--sky-deep);border:1px solid var(--sky-border)}
.gd-rail-link .tx{min-width:0}
.gd-rail-link .tx strong{display:block;font-size:.9rem;font-weight:600;color:var(--ink-2);line-height:1.3}
.gd-rail-link .tx span{font-size:.78rem;color:var(--muted)}
.gd-rail-link .ar{margin-left:auto;color:var(--muted-2);transition:transform .15s,color .15s;flex-shrink:0}
.gd-rail-link:hover .ar{color:var(--sky);transform:translateX(2px)}

/* Eye-catching keyworded CTA pinned at the bottom of the rail */
.gd-rail-cta{position:relative;border-radius:16px;overflow:hidden;background:linear-gradient(150deg,#0A1322,#13243d);color:#fff;padding:20px;border:1px solid rgba(56,189,248,.16);box-shadow:0 26px 50px -28px rgba(2,40,80,.6)}
.gd-rail-cta::before{content:'';position:absolute;inset:0;background:radial-gradient(90% 80% at 88% 4%,rgba(56,189,248,.5),transparent 54%),radial-gradient(80% 80% at 4% 110%,rgba(14,165,233,.32),transparent 56%);opacity:.95}
.gd-rail-cta>*{position:relative;z-index:1}
.gd-rail-cta .g{display:inline-flex;align-items:center;gap:8px;margin-bottom:12px}
.gd-rail-cta .g .grade{width:36px;height:36px;border-radius:11px;display:flex;align-items:center;justify-content:center;font-family:'JetBrains Mono',monospace;font-weight:700;font-size:1.05rem;color:#fff;background:linear-gradient(140deg,var(--sky),var(--sky-600));box-shadow:0 10px 20px -8px rgba(14,165,233,.7)}
.gd-rail-cta .g .scale{font-family:'JetBrains Mono',monospace;font-size:.74rem;color:#7C8AA5;letter-spacing:.04em}
.gd-rail-cta h4{font-size:1.08rem;font-weight:700;color:#fff;line-height:1.3;margin-bottom:6px;text-wrap:balance}
.gd-rail-cta p{font-size:.85rem;color:#9FB0C9;line-height:1.55;margin-bottom:15px}
.gd-rail-cta a{display:inline-flex;align-items:center;gap:8px;font-size:.9rem;font-weight:600;color:var(--ink);background:#fff;padding:11px 16px;border-radius:11px;width:100%;justify-content:center;transition:transform .15s,box-shadow .15s}
.gd-rail-cta a:hover{transform:translateY(-1px);box-shadow:0 12px 24px -10px rgba(0,0,0,.5)}

/* ── Continue learning (premium, wide) ── */
.gd-continue{padding:3.5rem 0 4.5rem;background:linear-gradient(180deg,var(--surface-3),#fff);border-top:1px solid var(--line)}
.gd-continue .container{position:relative}
.gd-continue-head{margin-bottom:1.8rem}
.gd-continue-head .k{display:inline-flex;align-items:center;gap:8px;font-size:.74rem;font-weight:700;text-transform:uppercase;letter-spacing:.1em;color:var(--sky-deep);margin-bottom:.7rem}
.gd-continue-head .k::before{content:'';width:18px;height:2px;background:var(--sky);border-radius:2px}
.gd-continue-head h2{font-size:clamp(1.5rem,3vw,2rem);letter-spacing:-.025em;color:var(--ink);font-weight:800;line-height:1.15}
.gd-cont-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
@media (max-width:900px){.gd-cont-grid{grid-template-columns:1fr 1fr}}
@media (max-width:620px){.gd-cont-grid{grid-template-columns:1fr}}
.gd-cont-card{display:flex;flex-direction:column;border:1px solid var(--line);border-radius:18px;background:#fff;padding:24px;box-shadow:var(--card);transition:transform .2s,box-shadow .2s,border-color .2s;color:inherit}
.gd-cont-card:hover{transform:translateY(-4px);border-color:var(--sky-border);box-shadow:0 24px 46px -24px rgba(2,40,80,.3)}
.gd-cont-card .ic{width:46px;height:46px;border-radius:13px;display:flex;align-items:center;justify-content:center;background:var(--sky-bg);color:var(--sky-deep);border:1px solid var(--sky-border);margin-bottom:15px}
.gd-cont-meta{display:flex;align-items:center;gap:9px;margin-bottom:9px}
.gd-cont-meta .lvl{font-size:.66rem;font-weight:700;text-transform:uppercase;letter-spacing:.04em;padding:2px 8px;border-radius:5px;background:var(--sky-bg);border:1px solid var(--sky-border);color:var(--sky-deep)}
.gd-cont-meta time{font-size:.78rem;color:var(--muted)}
.gd-cont-card h3{font-size:1.12rem;color:var(--ink);font-weight:700;letter-spacing:-.01em;line-height:1.3;margin-bottom:8px;text-wrap:balance}
.gd-cont-card p{font-size:.9rem;color:var(--body-2);line-height:1.55;flex:1;text-wrap:pretty}
.gd-cont-card .rm{margin-top:15px;font-size:.86rem;font-weight:600;color:var(--sky-deep);display:inline-flex;align-items:center;gap:6px}
.gd-cont-card .rm svg{transition:transform .18s}.gd-cont-card:hover .rm svg{transform:translateX(3px)}

/* ── FAQ ── */
.gd-faq{padding:1rem 0 1.5rem;background:#fff}
.gd-faq-inner{max-width:820px}
.gd-faq h2{font-size:clamp(1.5rem,2.8vw,1.95rem);letter-spacing:-.02em;color:var(--ink);font-weight:800;margin-bottom:1.3rem}
.gd-faq-grid{display:grid;gap:11px}
.gd-faq-item{border:1px solid var(--line);border-radius:14px;padding:18px 20px;background:#fff;transition:border-color .15s,box-shadow .15s}
.gd-faq-item:hover{border-color:var(--sky-border);box-shadow:0 12px 26px -20px rgba(15,23,42,.3)}
.gd-faq-q{display:flex;gap:11px;font-weight:700;color:var(--ink);font-size:1.05rem;line-height:1.4;margin-bottom:9px}
.gd-faq-q::before{content:'Q';font-family:'JetBrains Mono',monospace;font-size:.78rem;font-weight:700;color:var(--sky-deep);background:var(--sky-bg);border:1px solid var(--sky-border);border-radius:7px;width:24px;height:24px;display:inline-flex;align-items:center;justify-content:center;flex-shrink:0}
.gd-faq-a{font-size:.98rem;line-height:1.7;color:var(--body-2);padding-left:35px}
.gd-faq-a a{color:var(--sky-deep);text-decoration:underline;text-decoration-color:var(--sky-border);text-underline-offset:2px}
.gd-faq-a code{font-family:'JetBrains Mono',monospace;font-size:.85em;background:var(--surface-2);color:var(--ink-2);border:1px solid var(--line);padding:1px 5px;border-radius:5px}

@media (prefers-reduced-motion:reduce){.gd-progress{transition:none}}