/* Unified Blog Theme - Vivid Slate */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

:root{
  --bg:#0f1117;
  --bg-2:#171a24;
  --card:#1e2230;
  --card-2:#252a3a;
  --card-solid:#1e2230;
  --border:#2f3548;
  --border-strong:#404863;
  --text:#eef1f8;
  --text-2:#c8cee0;
  --muted:#8b93ac;
  --a:#6c8cff;
  --a2:#a78bfa;
  --g:#34d399;
  --y:#fbbf24;
  --r:#f87171;
  --o:#fb923c;
  --c:#22d3ee;
  --p:#f472b6;
  --t:#2dd4bf;
  --shadow:0 1px 2px rgba(0,0,0,.3),0 10px 28px -14px rgba(0,0,0,.5);
}

*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;color-scheme:dark}
body{
  font-family:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',system-ui,sans-serif;
  background:var(--bg);
  color:var(--text);
  line-height:1.7;
  font-size:15.5px;
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
  text-rendering:optimizeLegibility;
  font-feature-settings:'cv02','cv11','ss01','tnum';
}
a{color:var(--a);text-decoration:none;transition:color .15s}
a:hover{text-decoration:underline;text-underline-offset:3px;color:var(--a2)}
b,strong{color:#fff;font-weight:600}
::selection{background:rgba(108,140,255,.32);color:#fff}

.hi{color:var(--y);font-weight:600}.hg{color:var(--g);font-weight:600}.hr{color:var(--r);font-weight:600}
.hc{color:var(--c);font-weight:600}.hp{color:var(--p);font-weight:600}.ho{color:var(--o);font-weight:600}
.ha{color:var(--a);font-weight:600}.hv{color:var(--a2);font-weight:600}

/* ── Site Header / Navigation ─────────────────────────────────── */
.sh{
  position:sticky;top:0;z-index:200;
  background:rgba(15,17,23,.95);
  backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);
  border-bottom:1px solid rgba(47,53,72,.4);
  display:flex;align-items:center;justify-content:space-between;
  padding:0 24px;
  height:54px;
}
.sh-brand{
  font-size:1.05rem;font-weight:800;color:var(--text);
  text-decoration:none;letter-spacing:-.03em;
  
}
.sh-brand:hover{color:var(--a);text-decoration:none}
.sh-brand{display:flex;align-items:center;gap:8px}
.sh-logo{flex-shrink:0}
@keyframes shLogoSpin{from{transform:rotate(0deg)}to{transform:rotate(360deg)}}

.sh-nav{display:flex;align-items:center;gap:2px;margin-left:32px}

/* Right side group (premium + auth) */
.sh-right{display:flex;align-items:center;gap:10px;margin-left:auto}
.sh-link{
  padding:7px 14px;border-radius:8px;
  color:var(--muted);text-decoration:none;font-weight:500;font-size:.8rem;
  transition:color .15s,background .15s;
  
}
.sh-link:hover{color:var(--text);background:rgba(255,255,255,.06);text-decoration:none}

.sh-active{color:#fff;background:rgba(108,140,255,.12);font-weight:600}
.sh-active:hover{background:rgba(108,140,255,.18)}

/* Premium button in header */
.sh-premium-btn{padding:5px 12px;border-radius:5px;border:1px solid rgba(108,140,255,.4);background:rgba(108,140,255,.08);color:var(--a);font-size:.7rem;font-weight:600;cursor:pointer;transition:all .2s;white-space:nowrap;letter-spacing:.2px}
.sh-premium-btn:hover{background:var(--a);color:#fff;border-color:var(--a);box-shadow:0 2px 10px rgba(108,140,255,.3)}

/* Mobile */
.sh-toggle{display:none;background:none;border:none;color:var(--text);font-size:1.3rem;cursor:pointer;padding:6px}
@media(max-width:700px){
  .sh{padding:0 16px;flex-wrap:wrap;height:auto;padding-top:10px;padding-bottom:10px}
  .sh-toggle{display:block}
  .sh-nav{display:none;width:100%;padding-top:8px;flex-direction:column;align-items:stretch;gap:2px;order:3;margin-left:0}
  .sh-nav.sh-open{display:flex}
  .sh-link{text-align:center;padding:10px 14px;justify-content:center;font-size:.85rem}
  .sh-active{background:rgba(108,140,255,.1)}
}

/* ── Hero ─────────────────────────────────────────────────────── */
.hero{
  display:flex;flex-direction:column;align-items:center;justify-content:center;
  text-align:center;padding:40px 24px 28px;
  background:var(--bg-2);
  border-bottom:1px solid var(--border);
  width:100%;
}
.hero h1{font-size:1.8rem;font-weight:800;letter-spacing:-.02em;color:#fff;margin:0;width:100%;text-align:center}
.hero h1 span{background:linear-gradient(to right,var(--a),var(--a2));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;position:relative;display:inline-block}
.hero h1 span::after{content:'';position:absolute;left:0;bottom:-6px;width:100%;height:8px;background:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 200 8'%3E%3Cpath d='M0,4 Q25,0 50,4 T100,4 T150,4 T200,4' fill='none' stroke='%236c8cff' stroke-width='2' stroke-linecap='round'/%3E%3C/svg%3E") repeat-x;background-size:200px 8px;animation:heroUnderlineDraw .8s ease-out forwards,heroUnderlineShimmer 3s ease-in-out .8s infinite}
@keyframes heroUnderlineDraw{from{clip-path:inset(0 100% 0 0)}to{clip-path:inset(0 0 0 0)}}
@keyframes heroUnderlineShimmer{0%,100%{opacity:.7;transform:translateX(0)}50%{opacity:1;transform:translateX(3px)}}
.hero p{color:var(--muted);margin-top:8px;font-size:.88rem;line-height:1.5;width:100%;text-align:center}

/* ── Module nav grid (top) ────────────────────────────────────── */
.ng{
  margin:0;padding:18px 32px 22px;
  column-width:260px;
  column-gap:28px;
  column-rule:1px solid var(--border);
  overflow:hidden;
}
.nc{
  display:inline-block;
  width:100%;
  margin:0 0 10px;
  break-inside:avoid;
  -webkit-column-break-inside:avoid;
  page-break-inside:avoid;
  background:var(--card);
  border:1px solid var(--border);
  border-radius:8px;
  padding:0;
  transition:border-color .15s,background .15s;
  overflow:hidden;
}
.nc:hover{border-color:var(--border-strong)}
.nc h3{
  font-size:.78rem;
  text-transform:uppercase;
  letter-spacing:.8px;
  margin:0;
  padding:10px 14px;
  font-weight:600;
  user-select:none;
  display:flex;align-items:center;gap:8px;
  color:var(--text-2);
}
.nc h3:hover{color:#fff;background:var(--card-2)}
.nc-body{padding:0 12px 12px;display:flex;flex-direction:column;gap:6px}
.nc .lk,.nc .sg{display:flex;flex-wrap:wrap;gap:5px}
.nc .sg{padding:6px 8px;border-radius:6px;background:rgba(255,255,255,.025);border:1px solid var(--border)}
.nc .lk a,.nc .sg a{
  font-size:.78rem;
  padding:4px 10px;
  border-radius:6px;
  background:rgba(108,140,255,.08);
  border:1px solid rgba(108,140,255,.18);
  color:var(--text);
  transition:background .15s,border-color .15s,color .15s;
}
.nc .lk a:hover,.nc .sg a:hover{
  background:rgba(108,140,255,.18);
  border-color:var(--a);
  color:#fff;
  text-decoration:none;
}
.nc.active{border-color:var(--a);background:var(--card-2)}
.nc.active h3{color:#fff}

/* ── Content wrapper ──────────────────────────────────────────── */
.ct{margin:0;padding:0 32px 80px;max-width:none}

/* Section divider */
.sd{
  margin:36px 0 22px;
  padding:12px 16px;
  border-radius:8px;
  font-size:1rem;
  font-weight:600;
  letter-spacing:.4px;
  display:flex;align-items:center;gap:12px;
  background:var(--card);
  border:1px solid var(--border);
  border-left:3px solid var(--a);
  color:var(--text);
}
.sd .e{font-size:1.2rem}

/* ── Topic boxes ──────────────────────────────────────────────── */
.T{
  background:var(--card);
  border:1px solid var(--border);
  border-radius:10px;
  padding:22px 26px;
  margin-bottom:18px;
  box-shadow:var(--shadow);
}
.T > svg:not([style]){
  display:block;margin:6px auto 10px;max-width:280px;width:100%;height:auto;
}
.T h2{
  font-size:1.25rem;font-weight:700;margin-bottom:6px;letter-spacing:-.01em;color:#fff;
}
.T .su{
  color:var(--muted);font-size:.92rem;margin-bottom:16px;font-style:italic;
}

/* Tables */
.T table{
  width:100%;border-collapse:separate;border-spacing:0;margin:14px 0;font-size:.92rem;
  border:1px solid var(--border);border-radius:8px;overflow:hidden;
}
.T th{
  text-align:left;padding:10px 14px;background:var(--card-2);
  border-bottom:1px solid var(--border-strong);font-weight:600;color:var(--text);
  font-size:.78rem;text-transform:uppercase;letter-spacing:.6px;
}
.T td{padding:10px 14px;border-bottom:1px solid var(--border);vertical-align:top;color:var(--text-2)}
.T tr:last-child td{border-bottom:none}
.T tbody tr:nth-child(even) td{background:rgba(255,255,255,.018)}
.T tr:hover td{background:rgba(108,140,255,.05);color:var(--text)}
.T ul,.T ol{padding-left:22px;margin:10px 0}
.T li{margin-bottom:6px;color:var(--text-2)}
.T p{color:var(--text-2)}

/* Code */
pre{
  background:#0f1218;border:1px solid var(--border);border-radius:8px;
  padding:14px 16px;overflow-x:auto;font-size:.86rem;line-height:1.65;
  font-family:'JetBrains Mono',Consolas,'Cascadia Code',monospace;margin:12px 0;color:#dde3eb;
}
code{
  font-family:'JetBrains Mono',Consolas,'Cascadia Code',monospace;
  background:rgba(108,140,255,.10);border:1px solid rgba(108,140,255,.20);
  padding:1px 6px;border-radius:4px;font-size:.86rem;color:#bce0e8;
}
pre code{background:none;padding:0;border:none;color:inherit}

/* Callouts */
.b{
  border-radius:8px;padding:12px 16px;margin:14px 0;font-size:.92rem;
  border:1px solid var(--border);border-left-width:3px;color:var(--text-2);
}
.bb{background:rgba(155,199,224,.06);border-left-color:var(--c)}
.bg{background:rgba(143,209,158,.06);border-left-color:var(--g)}
.by{background:rgba(216,192,117,.06);border-left-color:var(--y)}
.br{background:rgba(226,146,146,.06);border-left-color:var(--r)}
.bp{background:rgba(184,168,212,.06);border-left-color:var(--p)}
.bo{background:rgba(214,164,122,.06);border-left-color:var(--o)}

.cols{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:12px 0}
@media(max-width:700px){.cols{grid-template-columns:1fr}}

.tg,.tr{display:inline-block;font-size:.72rem;padding:2px 9px;border-radius:999px;font-weight:600;margin-right:4px;border:1px solid}
.tg{background:rgba(143,209,158,.10);color:var(--g);border-color:rgba(143,209,158,.30)}
.tr{background:rgba(226,146,146,.10);color:var(--r);border-color:rgba(226,146,146,.30)}

/* Top button */
#topBtn{
  position:fixed;bottom:24px;right:24px;z-index:999;
  width:42px;height:42px;border-radius:50%;
  background:var(--a);color:var(--bg);border:none;cursor:pointer;
  font-size:1.2rem;font-weight:700;
  display:none;align-items:center;justify-content:center;
  box-shadow:var(--shadow);transition:transform .15s;
}
#topBtn:hover{transform:translateY(-2px)}

/* Section header colors */
.sd-1{border-left-color:var(--c)}
.sd-2{border-left-color:var(--r)}
.sd-3{border-left-color:var(--g)}
.sd-4{border-left-color:var(--p)}
.sd-5{border-left-color:var(--a)}
.sd-6{border-left-color:var(--g)}
.sd-7{border-left-color:var(--y)}
.sd-8{border-left-color:var(--o)}
.sd-9{border-left-color:var(--p)}
.sd-10{border-left-color:var(--t)}
.sd-11{border-left-color:var(--o)}
.sd-12{border-left-color:var(--a2)}
.sd-13{border-left-color:var(--c)}

.breadcrumb{padding:12px 32px;font-size:.88rem;color:var(--muted)}
.breadcrumb a{color:var(--a)}

/* ── Search ───────────────────────────────────────────────────── */
.search-wrap{max-width:680px;margin:18px auto 4px;padding:0 32px;position:relative}
.search-box{
  width:100%;padding:11px 16px;border-radius:8px;border:1px solid var(--border-strong);
  background:var(--card);color:var(--text);font-size:.95rem;outline:none;
  transition:border-color .15s,box-shadow .15s;
}
.search-box:focus{border-color:var(--a);box-shadow:0 0 0 3px rgba(108,140,255,.18)}
.search-box::placeholder{color:var(--muted)}
.search-results{
  position:absolute;top:100%;left:32px;right:32px;
  background:var(--card);border:1px solid var(--border-strong);
  border-radius:8px;margin-top:4px;max-height:380px;overflow-y:auto;display:none;z-index:100;
  box-shadow:var(--shadow);
}
.sr-item{display:flex;align-items:center;gap:10px;padding:10px 16px;text-decoration:none;color:var(--text);transition:background .12s;border-bottom:1px solid var(--border)}
.sr-item:last-child{border-bottom:none}
.sr-item:hover{background:rgba(108,140,255,.08);text-decoration:none}
.sr-cat{font-size:.7rem;text-transform:uppercase;letter-spacing:.5px;color:var(--muted);min-width:100px;flex-shrink:0}
.sr-text{font-size:.88rem;color:var(--a)}
.sr-empty{padding:14px 16px;color:var(--muted);font-size:.88rem;text-align:center}

/* ── Right rail ───────────────────────────────────────────────── */
#pageRail{
  position:fixed;top:84px;right:14px;width:260px;max-height:calc(100vh - 110px);
  overflow-y:auto;padding:14px 12px 16px;background:var(--card);
  border:1px solid var(--border-strong);border-radius:10px;z-index:50;
  font-size:.82rem;line-height:1.45;box-shadow:var(--shadow);display:none;
  transform:translateX(8px);opacity:0;transition:transform .18s ease, opacity .18s ease;
}
#pageRail.pr-visible{display:block;transform:none;opacity:1}
#pageRail h4{
  margin:0 0 10px;font-size:.7rem;letter-spacing:.7px;text-transform:uppercase;
  color:var(--a);font-weight:700;
  padding-bottom:8px;border-bottom:1px solid var(--border);
}
#pageRail h4 .pr-dot{width:6px;height:6px;border-radius:50%;background:var(--a)}
#pageRail ol{list-style:none;padding:0;margin:0;counter-reset:pr}
#pageRail li{counter-increment:pr;margin:0}
#pageRail a{
  display:block;padding:6px 8px 6px 26px;border-radius:5px;
  color:var(--text-2);text-decoration:none;position:relative;border-left:2px solid transparent;
  transition:background .12s,color .12s,border-color .12s;
}
#pageRail a::before{
  content:counter(pr);position:absolute;left:8px;top:6px;
  font-size:.7rem;color:var(--muted);font-weight:600;font-variant-numeric:tabular-nums;
}
#pageRail a:hover{background:var(--card-2);color:#fff}
#pageRail a.pr-active{background:rgba(108,140,255,.12);color:#fff;border-left-color:var(--a);font-weight:600}
#pageRail a.pr-active::before{color:var(--a)}
#pageRail::-webkit-scrollbar{width:6px}
#pageRail::-webkit-scrollbar-thumb{background:var(--border-strong);border-radius:3px}

#pr-toggle{
  position:fixed;top:84px;right:14px;z-index:51;
  display:inline-flex;align-items:center;gap:8px;
  padding:8px 12px;border-radius:8px;border:1px solid var(--border-strong);
  background:var(--card);color:var(--text);cursor:pointer;font:inherit;
  font-size:.78rem;font-weight:600;letter-spacing:.4px;box-shadow:var(--shadow);
  transition:background .15s,border-color .15s,color .15s,transform .12s;
}
#pr-toggle:hover{background:var(--card-2);color:#fff;border-color:var(--a)}
#pr-toggle .pr-tog-ic{font-size:1rem;line-height:1}
#pr-toggle.pr-tog-open{background:var(--a);color:#0f1117;border-color:var(--a)}
#pr-toggle.pr-tog-open:hover{background:var(--a2);border-color:var(--a2);color:#0f1117}
#pageRail.pr-visible ~ #pr-toggle{right:286px}
@media(max-width:600px){
  #pr-toggle .pr-tog-lbl{display:none}
  #pr-toggle{padding:8px 10px}
}

/* ── Real-time problems specific ──────────────────────────────── */
.category-title{color:var(--y);font-size:2.2em;margin:0 0 8px;font-weight:700}
.category-desc{color:var(--muted);font-size:1.1em;margin:0 0 40px}
.problems-list{display:flex;flex-direction:column;gap:32px}
.problem-card{
  background:var(--card);border:1px solid var(--border);border-radius:12px;
  padding:24px;transition:all 0.3s ease;box-shadow:var(--shadow);
}
.problem-card:hover{border-color:var(--a);box-shadow:0 8px 24px rgba(108,140,255,0.2)}
.problem-num{
  display:inline-flex;align-items:center;justify-content:center;
  background:var(--a);color:white;width:32px;height:32px;border-radius:50%;
  font-weight:700;font-size:0.9em;margin-bottom:12px;
}
.problem-title{color:var(--y);font-size:1.3em;margin:12px 0 12px;font-weight:600}
.problem-constraint{
  background:rgba(108,140,255,0.08);border-left:3px solid var(--a);
  padding:12px 16px;margin:16px 0;border-radius:4px;font-size:0.95em;border:1px solid var(--border);
}
.problem-constraint strong{color:var(--y)}
.topics-list{display:flex;flex-wrap:wrap;gap:8px;margin:16px 0}
.topic-tag{
  background:rgba(107,114,128,0.2);border:1px solid rgba(107,114,128,0.4);
  color:var(--text);padding:6px 12px;border-radius:20px;font-size:0.85em;
}
.solution-section{
  background:rgba(52,211,153,0.06);border-left:3px solid var(--g);
  padding:16px;margin-top:16px;border-radius:8px;border:1px solid var(--border);
}
.solution-section h4{color:var(--g);margin:0 0 8px;font-size:0.95em;text-transform:uppercase;letter-spacing:0.5px;font-weight:600}
.solution-text{font-size:0.95em;line-height:1.7;color:var(--text)}
.architecture-points{list-style:none;padding:0;margin:12px 0 0}
.architecture-points li{padding:6px 0 6px 24px;position:relative;font-size:0.9em}
.architecture-points li:before{content:"→";position:absolute;left:0;color:var(--g);font-weight:bold}
.nav-links{display:flex;justify-content:space-between;margin-top:40px;padding-top:40px;border-top:1px solid var(--border)}
.nav-links a{
  padding:12px 24px;background:var(--card);border:1px solid var(--border);
  border-radius:8px;color:var(--a);text-decoration:none;transition:all 0.3s;
}
.nav-links a:hover{background:var(--a);color:white;border-color:var(--a)}

/* ── Index page cards ─────────────────────────────────────────── */
.intro-section{margin-top:60px;padding-top:40px;border-top:1px solid var(--border)}
.intro-section h2{color:var(--y);margin-bottom:24px;font-weight:700;font-size:1.5rem}
.intro-content{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:20px;margin-bottom:40px}
.intro-card{background:var(--card);border:1px solid var(--border);border-radius:8px;padding:20px}
.intro-card h3{color:var(--a);margin-top:0;font-weight:600;font-size:1rem}
.intro-card p{color:var(--text-2);margin:8px 0}
.intro-card ul{list-style:none;padding:0;margin:0}
.intro-card li{padding:6px 0;padding-left:20px;position:relative;color:var(--text-2)}
.intro-card li:before{content:"▸";position:absolute;left:0;color:var(--a)}
.stats-table{width:100%;border-collapse:collapse;margin:24px 0;background:var(--card);border:1px solid var(--border);border-radius:8px;overflow:hidden}
.stats-table td{padding:16px 20px;border-bottom:1px solid var(--border);color:var(--text-2)}
.stats-table tr:last-child td{border-bottom:none}
.stats-table td:first-child{color:var(--y);font-weight:600;width:30%}
.scale-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:16px;margin:24px 0}
.scale-card{background:var(--card);border-left:4px solid var(--a);border-radius:8px;padding:20px;border:1px solid var(--border)}
.scale-card h3{color:var(--y);margin:0 0 8px;font-weight:600}
.scale-card p{margin:6px 0;font-size:0.9em;color:var(--text-2)}
.scale-card .topics{color:var(--muted);font-size:0.85em;font-style:italic}

/* ── Blog home page cards ─────────────────────────────────────── */
.blog-sections{
  display:grid;grid-template-columns:repeat(auto-fit,minmax(340px,1fr));
  gap:24px;padding:32px;max-width:1200px;margin:0 auto;
}
.blog-card{
  background:var(--card);border:1px solid var(--border);border-radius:12px;
  padding:28px;transition:all .2s;box-shadow:var(--shadow);
  display:flex;flex-direction:column;gap:12px;
}
.blog-card:hover{border-color:var(--a);transform:translateY(-2px);box-shadow:0 12px 32px rgba(108,140,255,.15)}
.blog-card h2{font-size:1.3rem;color:#fff;margin:0}
.blog-card p{color:var(--text-2);font-size:.92rem;margin:0;flex:1}
.blog-card .card-meta{display:flex;align-items:center;gap:8px;margin-top:8px}
.blog-card .card-tag{
  font-size:.72rem;padding:3px 10px;border-radius:999px;font-weight:600;
  background:rgba(108,140,255,.1);color:var(--a);border:1px solid rgba(108,140,255,.25);
}
.blog-card .card-link{
  display:inline-flex;align-items:center;gap:6px;
  padding:8px 16px;border-radius:8px;background:rgba(108,140,255,.1);
  border:1px solid rgba(108,140,255,.25);color:var(--a);font-weight:600;font-size:.85rem;
  text-decoration:none;transition:all .15s;margin-top:auto;align-self:flex-start;
}
.blog-card .card-link:hover{background:var(--a);color:#fff;border-color:var(--a);text-decoration:none}

/* ── Responsive ───────────────────────────────────────────────── */
@media(max-width:900px){
  .hero{padding:32px 16px 20px}
  .hero h1{font-size:1.5rem}
  .ng{column-width:220px;padding:14px 16px}
  .ct{padding:0 16px 60px}
  .sd{margin:28px 0 18px;padding:10px 14px;font-size:.95rem}
  .T{padding:18px 18px}
  .T table{font-size:.86rem}
  .T th,.T td{padding:8px 10px}
  pre{font-size:.8rem;padding:10px 12px}
  .search-wrap{padding:0 16px}
  .search-results{left:16px;right:16px}
  .breadcrumb{padding:10px 16px}
  .blog-sections{padding:20px 16px;gap:16px}
}

@media(max-width:600px){
  body{font-size:14.5px}
  .hero{padding:28px 12px 20px}
  .hero h1{font-size:1.35rem}
  .hero p{font-size:.82rem}
  .ng{column-width:100%;column-gap:0;column-rule:none;padding:10px}
  .nc h3{font-size:.74rem;padding:9px 12px}
  .ct{padding:0 12px 50px}
  .sd{font-size:.9rem;padding:9px 12px;margin:24px 0 16px}
  .T{padding:14px 14px;margin-bottom:14px}
  .T h2{font-size:1.1rem}
  .T .su{font-size:.84rem;margin-bottom:12px}
  .T table{font-size:.8rem;display:block;overflow-x:auto;-webkit-overflow-scrolling:touch}
  .T th,.T td{padding:6px 8px;white-space:nowrap}
  pre{font-size:.78rem;padding:10px 12px}
  code{font-size:.8rem}
  .b{padding:10px 12px;font-size:.86rem}
  .cols{grid-template-columns:1fr;gap:10px}
  .search-box{font-size:.9rem;padding:10px 14px}
  .sr-cat{min-width:70px;font-size:.65rem}
  .sr-text{font-size:.82rem}
  #topBtn{bottom:16px;right:16px;width:38px;height:38px;font-size:1.05rem}
  svg{max-width:100%!important}
  .nc .sg{padding:4px 6px}
  .nc .lk a,.nc .sg a{font-size:.74rem;padding:3px 8px}
  .blog-sections{grid-template-columns:1fr;padding:16px 12px}
  .intro-content{grid-template-columns:1fr}
  .scale-grid{grid-template-columns:1fr}
  .nav-links{flex-direction:column;gap:12px}
  .nav-links a{text-align:center}
}

@media(max-width:400px){
  .hero h1{font-size:1.2rem}
  .nc h3{font-size:.7rem;letter-spacing:.6px}
  .nc .lk a,.nc .sg a{font-size:.7rem;padding:3px 7px}
  pre{font-size:.74rem}
}

@media print{
  body{background:#fff;color:#111}
  .T,.nc,.sd{border:1px solid #ddd;background:#fff;box-shadow:none}
  pre{background:#f5f5f5}
  #topBtn,#pageRail,#pr-toggle,.sh{display:none!important}
}

/* ── Site Footer ──────────────────────────────────────────────── */
.site-footer{text-align:center;padding:28px 24px;border-top:1px solid var(--border);color:var(--muted);font-size:.75rem;margin-top:40px;clear:both;width:100%}
.site-footer p{margin:0}
.site-footer a{color:var(--a);text-decoration:none}
.site-footer a:hover{text-decoration:underline}

/* ── Concepts Involved (expandable on problem pages) ─────────── */
.concepts-involved{margin:10px 0 14px;border:1px solid var(--border);border-radius:8px;background:var(--card);overflow:hidden}
.concepts-involved summary{padding:10px 16px;font-size:.78rem;font-weight:600;color:var(--text);cursor:pointer;list-style:none;display:flex;align-items:center;gap:6px;transition:background .15s}
.concepts-involved summary::-webkit-details-marker{display:none}
.concepts-involved summary::after{content:'';display:inline-block;width:14px;height:14px;margin-left:6px;background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%238b8fa3' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M1 12s4-8 11-8 11 8 11 8-4 8-11 8-11-8-11-8z'/%3E%3Ccircle cx='12' cy='12' r='3'/%3E%3C/svg%3E");background-size:contain;background-repeat:no-repeat;opacity:.6;transition:opacity .15s}
.concepts-involved[open] summary::after{background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%236c8cff' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M17.94 17.94A10.07 10.07 0 0 1 12 20c-7 0-11-8-11-8a18.45 18.45 0 0 1 5.06-5.94M9.9 4.24A9.12 9.12 0 0 1 12 4c7 0 11 8 11 8a18.5 18.5 0 0 1-2.16 3.19m-6.72-1.07a3 3 0 1 1-4.24-4.24'/%3E%3Cline x1='1' y1='1' x2='23' y2='23'/%3E%3C/svg%3E");opacity:1}
.concepts-involved summary::before{display:none}
.concepts-involved summary:hover{background:rgba(108,140,255,.04)}
.concepts-involved summary:hover::after{opacity:1}
.concepts-involved-pills{display:flex;flex-wrap:wrap;gap:6px;padding:8px 16px 14px}
.concepts-involved-pills a{font-size:.7rem;padding:4px 10px;border-radius:5px;background:rgba(108,140,255,.08);color:var(--a);font-weight:500;border:1px solid rgba(108,140,255,.15);text-decoration:none;transition:all .15s}
.concepts-involved-pills a:hover{background:rgba(108,140,255,.18);border-color:var(--a);text-decoration:none;transform:translateY(-1px)}

/* ── Prev / Next Page Navigation ─────────────────────────────── */
.page-nav{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:16px 24px;margin-top:24px;border-top:1px solid var(--border)}
.page-nav-btn{display:flex;align-items:center;gap:8px;padding:10px 16px;border-radius:8px;border:1px solid var(--border);background:rgba(255,255,255,.02);text-decoration:none;transition:all .15s}
.page-nav-btn:hover{border-color:var(--a);background:rgba(108,140,255,.04);text-decoration:none}
.page-nav-prev{margin-right:auto}
.page-nav-next{margin-left:auto}
.page-nav-dir{font-size:.7rem;color:var(--muted)}
.page-nav-title{font-size:.8rem;font-weight:600;color:var(--text)}
.page-nav-btn:hover .page-nav-title{color:var(--a)}
@media(max-width:500px){.page-nav-btn{padding:8px 12px}.page-nav-title{font-size:.75rem}}

/* ── Premium CTA (center of page-nav) ────────────────────────── */
.page-nav-cta{display:flex;align-items:center;justify-content:center;gap:10px;padding:6px 16px;border-radius:8px;background:linear-gradient(135deg,rgba(108,140,255,.06),rgba(167,139,250,.06));border:1px solid rgba(108,140,255,.15)}
.page-nav-cta-label{font-size:.72rem;color:var(--muted);white-space:nowrap}
.page-nav-cta-btn{padding:7px 16px;border-radius:6px;border:none;background:linear-gradient(135deg,var(--a),var(--a2));color:#fff;font-size:.72rem;font-weight:600;cursor:pointer;transition:all .15s;white-space:nowrap;box-shadow:0 2px 8px rgba(108,140,255,.3)}
.page-nav-cta-btn:hover{transform:translateY(-1px);box-shadow:0 4px 14px rgba(108,140,255,.4)}
@media(max-width:600px){.page-nav-cta{flex-direction:column;gap:4px;padding:6px 10px}.page-nav-cta-label{font-size:.65rem}}