/* ============================================================
   Zaid Mahboob — blog
   Self-contained navy theme, cohesive with the main site
   (css/home.css) and AI for Kids. Retuned for long-form reading.
   Token names (--accent, --panel-2, --line-2, --ink-mute …) are
   kept stable because js/blog-c3-demo.js reads them at runtime.
   ============================================================ */

:root {
  /* surfaces (navy — matches zaidmahboob.com) */
  --bg:        #051424;
  --bg-2:      #0a1a2b;
  --panel:     #122131;
  --panel-2:   #0d1c2d;
  --line:      #2a3a4e;
  --line-2:    #34475d;

  /* text */
  --ink:       #d4e4fa;
  --ink-dim:   #aeb9d0;
  --ink-mute:  #8b98b0;
  --primary:   #bec6e0;

  /* accents */
  --accent:    #7bd0ff;   /* sky blue — primary / QP / feasible */
  --accent-2:  #ffb95f;   /* amber — MIQP / infeasible */
  --accent-3:  #a78bfa;   /* violet — residual / dual / gap */

  --mono:    'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
  --display: 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --sans:    'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;

  --readw: 700px;          /* reading column */
  --widew: 940px;          /* figures may breach the column */

  /* semantic aliases used by technical posts */
  --c-qp:    var(--accent);
  --c-miqp:  var(--accent-2);
  --c-gap:   var(--accent-3);
  --c-qp-a:   rgba(123, 208, 255, .10);
  --c-miqp-a: rgba(255, 185, 95, .10);
  --c-gap-a:  rgba(167, 139, 250, .10);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
::selection { background: var(--accent); color: #00354a; }
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--line-2); border-radius: 4px; }

/* subtle dot grid, fading from the top — the site's technical motif */
.grid-bg {
  position: fixed; inset: 0; z-index: 0; pointer-events: none;
  background-image: radial-gradient(circle, var(--line) 1px, transparent 1px);
  background-size: 22px 22px; opacity: .5;
  mask-image: radial-gradient(ellipse 80% 55% at 50% 0%, #000 25%, transparent 85%);
  -webkit-mask-image: radial-gradient(ellipse 80% 55% at 50% 0%, #000 25%, transparent 85%);
}
.noise { display: none; }

/* ---------- blog top bar ---------- */
.bnav {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  padding: .85rem clamp(1.2rem, 4vw, 2.4rem);
  backdrop-filter: blur(10px);
  background: rgba(5, 20, 36, .82);
  border-bottom: 1px solid var(--line);
}
.bnav__back {
  font-family: var(--mono); font-size: .78rem; letter-spacing: .05em;
  color: var(--ink-dim); transition: color .2s;
  display: inline-flex; align-items: center; gap: .5rem;
}
.bnav__back:hover { color: var(--accent); }
.bnav__mark {
  font-family: var(--mono); font-weight: 700; letter-spacing: .1em; font-size: .8rem;
  border: 1px solid var(--accent); color: var(--accent);
  padding: .2rem .45rem; border-radius: 5px;
}
.bnav__links { display: flex; gap: 1.3rem; }
.bnav__links a {
  font-family: var(--mono); font-size: .76rem; color: var(--ink-dim);
  letter-spacing: .05em; transition: color .2s;
}
.bnav__links a:hover { color: var(--accent); }
@media (max-width: 620px) { .bnav__links { display: none; } }

/* ---------- shells ---------- */
.wrap  { position: relative; z-index: 1; max-width: var(--widew); margin: 0 auto; padding: 0 1.5rem 6rem; }
.col   { max-width: var(--readw); }
.post  { position: relative; z-index: 1; max-width: var(--readw); margin: 0 auto; padding: 0 1.5rem 6rem; }

.post .bleed {
  width: min(var(--widew), calc(100vw - 3rem));
  margin-left: 50%; transform: translateX(-50%);
}

/* ============================================================
   HUB
   ============================================================ */
.bhero { max-width: var(--widew); margin: 0 auto; padding: 5rem 1.5rem 3rem; position: relative; z-index: 1; }
.bhero__title {
  font-family: var(--display); font-weight: 800; letter-spacing: -.03em;
  font-size: clamp(2.4rem, 7vw, 4.2rem); line-height: .95; margin-top: 1.1rem;
  color: var(--primary); text-shadow: 0 0 60px rgba(123, 208, 255, .12);
}
.bhero__lede {
  color: var(--ink-dim); max-width: 56ch; margin-top: 1.4rem;
  font-size: clamp(1rem, 1.4vw, 1.12rem); line-height: 1.6;
}

.plist { display: flex; flex-direction: column; gap: 0; margin-top: 1rem; }

.pcard {
  display: grid; grid-template-columns: 4.2rem 1fr; gap: 1.6rem;
  padding: 2rem 1.2rem;
  border-top: 1px solid var(--line);
  transition: background .2s, border-color .2s;
}
.plist .pcard:last-child { border-bottom: 1px solid var(--line); }
.pcard:hover { background: var(--panel-2); border-color: var(--line-2); }
.pcard__num {
  font-family: var(--mono); font-size: .78rem; color: var(--ink-mute);
  letter-spacing: .1em; padding-top: .35rem;
}
.pcard:hover .pcard__num { color: var(--accent); }
.pcard__tags { display: flex; flex-wrap: wrap; gap: .45rem; margin-bottom: .75rem; }
.ptag {
  font-family: var(--mono); font-size: .66rem; letter-spacing: .12em; text-transform: uppercase;
  color: var(--ink-mute); border: 1px solid var(--line-2);
  padding: .18rem .5rem; border-radius: 999px;
}
.ptag--live { color: var(--accent); border-color: rgba(123, 208, 255, .4); }
.pcard__title {
  font-family: var(--display); font-weight: 700; letter-spacing: -.02em;
  font-size: clamp(1.25rem, 2.4vw, 1.65rem); line-height: 1.15; margin-bottom: .6rem;
  color: var(--primary);
}
.pcard:hover .pcard__title { color: var(--accent); }
.pcard__desc { color: var(--ink-dim); font-size: .96rem; max-width: 62ch; margin-bottom: .9rem; }
.pcard__meta { font-family: var(--mono); font-size: .72rem; color: var(--ink-mute); letter-spacing: .06em; }
.pcard__meta span + span::before { content: "·"; margin: 0 .55rem; color: var(--line-2); }

.pcard--soon { opacity: .5; }
.pcard--soon:hover { background: none; }
.pcard--soon .pcard__title { color: var(--ink); }

@media (max-width: 640px) {
  .pcard { grid-template-columns: 1fr; gap: .5rem; padding: 1.6rem .4rem; }
  .pcard__num { padding-top: 0; }
}

/* ============================================================
   POST
   ============================================================ */
.phead { padding: 4.5rem 0 0; margin-bottom: 3.5rem; }
.phead__eyebrow {
  font-family: var(--mono); font-size: .72rem; letter-spacing: .22em; text-transform: uppercase;
  color: var(--accent); display: inline-flex; align-items: center; gap: .6rem;
}
.phead__eyebrow::before { content: ""; width: 26px; height: 1px; background: var(--accent); display: inline-block; }
.phead__title {
  font-family: var(--display); font-weight: 800; letter-spacing: -.025em;
  font-size: clamp(2rem, 5.5vw, 3.1rem); line-height: 1.08; margin: 1.3rem 0 1.2rem;
  color: var(--primary); text-wrap: balance;
}
.phead__lede { color: var(--ink-dim); font-size: clamp(1.05rem, 1.6vw, 1.2rem); line-height: 1.6; max-width: 56ch; }
.phead__meta {
  display: flex; flex-wrap: wrap; gap: .5rem 0; margin-top: 2rem; padding-top: 1.3rem;
  border-top: 1px solid var(--line);
  font-family: var(--mono); font-size: .73rem; color: var(--ink-mute); letter-spacing: .06em;
}
.phead__meta span + span::before { content: "·"; margin: 0 .6rem; color: var(--line-2); }

@media (max-width: 620px) {
  .phead__meta { gap: .35rem 1.1rem; }
  .phead__meta span + span::before { content: none; }
  .pcard__meta span + span::before { content: none; }
  .pcard__meta span + span { margin-left: 1.1rem; }
}

/* prose */
.psec { margin-bottom: 4rem; }
.psec__head { display: flex; align-items: baseline; gap: 1rem; margin-bottom: 1.4rem; }
.psec__num {
  font-family: var(--mono); font-size: .74rem; color: var(--accent);
  letter-spacing: .1em; flex-shrink: 0; padding-top: .35rem;
}
.psec h2 {
  font-family: var(--display); font-weight: 700; letter-spacing: -.015em;
  font-size: clamp(1.35rem, 2.8vw, 1.75rem); line-height: 1.2; color: var(--primary); text-wrap: balance;
}
.psec h3 {
  font-family: var(--mono); font-size: .76rem; font-weight: 600; letter-spacing: .14em;
  text-transform: uppercase; color: var(--ink-mute); margin: 2rem 0 .7rem;
}
.post p { margin-bottom: 1.1rem; line-height: 1.78; color: var(--ink); }
.post p:last-child { margin-bottom: 0; }
.post strong { color: var(--ink); font-weight: 600; }
.post em { color: var(--ink-dim); }
.post a:not(.bnav__back):not(.pcard) { color: var(--accent); border-bottom: 1px solid rgba(123, 208, 255, .3); transition: border-color .2s; }
.post a:not(.bnav__back):not(.pcard):hover { border-color: var(--accent); }

code {
  font-family: var(--mono); font-size: .87em;
  background: var(--panel); border: 1px solid var(--line);
  padding: .1em .4em; border-radius: 4px; white-space: nowrap;
  color: var(--ink);
}
code.qp { color: var(--c-qp); }  code.miqp { color: var(--c-miqp); }

/* block equation */
.eq {
  font-family: var(--mono); font-size: .92rem; line-height: 2.1;
  background: var(--panel-2); border: 1px solid var(--line);
  border-left: 3px solid var(--c-gap);
  padding: 1.1rem 1.3rem; margin: 1.6rem 0;
  border-radius: 0 8px 8px 0; overflow-x: auto;
}
.eq .cm { color: var(--ink-mute); font-size: .82rem; }
.hq { color: var(--c-qp);   font-weight: 600; }
.hm { color: var(--c-miqp); font-weight: 600; }
.hg { color: var(--c-gap);  font-weight: 600; }

/* pull note */
.note {
  border-left: 2px solid var(--line-2); margin: 1.6rem 0; padding: .7rem 1.3rem;
  color: var(--ink-dim); font-size: .95rem; line-height: 1.7;
}

/* callout */
.callout {
  background: var(--c-miqp-a); border: 1px solid rgba(255, 185, 95, .35);
  border-radius: 10px; padding: 1.1rem 1.3rem; margin: 1.6rem 0;
  font-size: .96rem; line-height: 1.7;
}
.callout strong { color: var(--c-miqp); }

/* receding-horizon diagram */
.horizon {
  background: var(--panel-2); border: 1px solid var(--line);
  border-radius: 12px; padding: 1.3rem 1.4rem 1.1rem; margin: 1.6rem 0; overflow-x: auto;
}
.horizon__label {
  font-family: var(--mono); font-size: .68rem; color: var(--ink-mute);
  letter-spacing: .14em; text-transform: uppercase; margin-bottom: .9rem;
}
.horizon__row { display: flex; align-items: center; margin-bottom: .3rem; }
.hz {
  width: 58px; height: 32px; border: 1px solid var(--line-2);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--mono); font-size: .68rem; color: var(--ink-mute); flex-shrink: 0;
}
.hz--now { background: var(--c-qp-a); border-color: var(--c-qp); color: var(--c-qp); font-weight: 700; }
.hz--faded { opacity: .4; border-style: dashed; }
.horizon__cap { font-size: .85rem; color: var(--ink-mute); margin-top: .8rem; }

/* figure + caption side by side */
.fig { display: flex; align-items: flex-start; gap: 1.6rem; margin: 1.6rem 0; }
.fig svg { flex-shrink: 0; }
.fig__cap { font-size: .92rem; color: var(--ink-dim); line-height: 1.65; padding-top: .2rem; }
.fig__cap strong { color: var(--ink); }
@media (max-width: 560px) { .fig { flex-direction: column; } }

/* enumerated "why this is hard" block */
.reasons { margin: 1.8rem 0; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; }
.reasons__head {
  font-family: var(--mono); font-size: .68rem; letter-spacing: .14em; text-transform: uppercase;
  color: var(--ink-mute); background: var(--panel); padding: .75rem 1.1rem;
  border-bottom: 1px solid var(--line);
}
.reasons__item {
  display: flex; gap: 1rem; padding: 1rem 1.1rem;
  border-bottom: 1px solid var(--line); font-size: .95rem; line-height: 1.7;
}
.reasons__item:last-child { border-bottom: none; }
.reasons__num {
  font-family: var(--mono); font-size: .78rem; font-weight: 700; color: var(--c-miqp);
  flex-shrink: 0; width: 1.1rem; padding-top: .1rem;
}

/* two-column split (QP | MIQP) */
.split {
  display: grid; grid-template-columns: 1fr 2.4rem 1fr; margin: 1.8rem 0;
  border: 1px solid var(--line); border-radius: 12px; overflow: hidden;
}
.split__a, .split__b { padding: 1.2rem 1.3rem; }
.split__a { background: var(--c-qp-a);   border-right: 1px solid var(--line); }
.split__b { background: var(--c-miqp-a); }
.split__mid {
  display: flex; align-items: center; justify-content: center;
  background: var(--panel); color: var(--ink-mute); font-size: 1.1rem;
}
.split__label {
  font-family: var(--mono); font-size: .68rem; font-weight: 700;
  letter-spacing: .14em; text-transform: uppercase; margin-bottom: .6rem;
}
.split__a .split__label { color: var(--c-qp); }
.split__b .split__label { color: var(--c-miqp); }
.split__body { font-size: .9rem; line-height: 1.65; color: var(--ink-dim); }
.split__body strong { color: var(--ink); }
@media (max-width: 620px) {
  .split { grid-template-columns: 1fr; }
  .split__a { border-right: none; border-bottom: 1px solid var(--line); }
  .split__mid { padding: .5rem; border-bottom: 1px solid var(--line); font-size: 1rem; }
}
.split__note { text-align: center; font-size: .9rem; color: var(--ink-mute); margin-top: .8rem; font-style: italic; }
.split__note strong { color: var(--c-gap); font-style: normal; }

/* interactive demo */
.demo {
  display: grid; grid-template-columns: 1fr 200px; gap: 1.6rem; align-items: start;
  margin-top: 1.4rem;
}
@media (max-width: 620px) { .demo { grid-template-columns: 1fr; } }
.demo canvas {
  border: 1px solid var(--line); border-radius: 10px; display: block;
  max-width: 100%; background: var(--panel-2);
}
.dbtn {
  font-family: var(--mono); font-size: .72rem; font-weight: 700;
  letter-spacing: .1em; text-transform: uppercase;
  padding: .65rem 1rem; border-radius: 8px; border: 1px solid; cursor: pointer;
  width: 100%; transition: opacity .15s, background .15s;
}
.dbtn:hover { opacity: .8; }
.dbtn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.dbtn--run { background: var(--c-gap); color: #06131f; border-color: var(--c-gap); }
.dbtn--rst { background: transparent; color: var(--ink-mute); border-color: var(--line-2); margin-top: .5rem; }
.dbtn--rst:hover { color: var(--ink); }

.panelout {
  margin-top: 1rem; background: var(--panel-2); border: 1px solid var(--line);
  border-radius: 10px; padding: .8rem 1rem;
  font-family: var(--mono); font-size: .74rem; line-height: 2;
}
.panelout .k { color: var(--ink-mute); }
.vq { color: var(--c-qp); } .vm { color: var(--c-miqp); } .vg { color: var(--c-gap); }

.legend { margin-top: 1rem; display: flex; flex-direction: column; gap: .45rem; }
.legend__item { display: flex; align-items: center; gap: .6rem; font-size: .78rem; color: var(--ink-mute); }
.legend__dot  { width: 9px; height: 9px; border-radius: 50%; flex-shrink: 0; }
.legend__line { width: 15px; height: 2px; border-radius: 1px; flex-shrink: 0; }

/* results table */
.rtable { width: 100%; border-collapse: collapse; font-size: .93rem; margin: 1.6rem 0; }
.rtable th {
  font-family: var(--mono); font-size: .68rem; letter-spacing: .12em; text-transform: uppercase;
  color: var(--ink-mute); font-weight: 600; text-align: left;
  padding: .6rem .8rem; border-bottom: 2px solid var(--line-2);
}
.rtable td { padding: .75rem .8rem; border-bottom: 1px solid var(--line); vertical-align: top; color: var(--ink-dim); }
.rtable tr:last-child td { border-bottom: none; }
.rtable .metric { font-weight: 600; color: var(--ink); }
.rtable .good { color: var(--c-qp); font-weight: 700; }
.rtable .bad  { color: var(--c-miqp); font-weight: 600; }

/* footer / references */
.pfoot {
  margin-top: 4rem; padding-top: 1.6rem; border-top: 1px solid var(--line);
  font-size: .88rem; color: var(--ink-mute); line-height: 1.8;
}
.pfoot strong {
  display: block; font-family: var(--mono); font-size: .7rem; letter-spacing: .14em;
  text-transform: uppercase; color: var(--ink-dim); margin-bottom: .7rem;
}

.pnext {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  margin-top: 2.5rem; padding: 1.2rem 1.3rem;
  border: 1px solid var(--line); border-radius: 12px; background: var(--panel-2);
  font-family: var(--mono); font-size: .8rem; color: var(--ink-dim);
  transition: border-color .2s, color .2s;
}
.pnext:hover { border-color: var(--accent); color: var(--accent); }

@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }