/* ============================================================
   How LLMs Actually Work — site stylesheet
   Palette: paper #FBFAF6 · ink #1C2431 · marker #FFE24D
            teal #2E7D74 · rule #E4E1D6 · muted #5A6372
   Type:    Newsreader (display) · IBM Plex Sans (body)
            IBM Plex Mono (token chips, labels)
   ============================================================ */

:root{
  --paper:#FBFAF6;
  --ink:#1C2431;
  --muted:#5A6372;
  --marker:#FFE24D;
  --marker-soft:#FFF3B8;
  --teal:#2E7D74;
  --teal-dark:#22615A;
  --rule:#E4E1D6;
  --card:#FFFFFF;
  --max:1080px;
  --serif:"Newsreader",Georgia,serif;
  --sans:"IBM Plex Sans",-apple-system,"Segoe UI",sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,Menlo,monospace;
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}
}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:1.0625rem;
  line-height:1.65;
  -webkit-font-smoothing:antialiased;
}
img{max-width:100%;display:block}
a{color:var(--teal-dark);text-decoration-thickness:1px;text-underline-offset:3px}
a:hover{color:var(--ink)}
:focus-visible{outline:3px solid var(--teal);outline-offset:2px;border-radius:2px}

.wrap{max-width:var(--max);margin:0 auto;padding:0 1.25rem}

/* ---------- header ---------- */
.site-header{border-bottom:1px solid var(--rule);background:var(--paper);position:sticky;top:0;z-index:50}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;gap:1rem;padding-top:.8rem;padding-bottom:.8rem}
.logo{font-family:var(--mono);font-size:.95rem;font-weight:600;color:var(--ink);text-decoration:none;letter-spacing:-.01em}
.logo .tok{background:var(--marker);padding:.1em .3em;border-radius:4px}
.nav{display:flex;gap:1.4rem;align-items:center;flex-wrap:wrap}
.nav a{font-size:.95rem;text-decoration:none;color:var(--ink)}
.nav a:hover{text-decoration:underline;text-underline-offset:4px}
.nav .btn{padding:.45rem .9rem;font-size:.9rem}

/* ---------- buttons ---------- */
.btn{
  display:inline-block;background:var(--ink);color:#fff;
  font-family:var(--sans);font-weight:600;font-size:1rem;
  padding:.8rem 1.5rem;border-radius:8px;border:2px solid var(--ink);
  text-decoration:none;cursor:pointer;transition:background .15s,color .15s;
}
.btn:hover{background:var(--marker);color:var(--ink)}
.btn-ghost{background:transparent;color:var(--ink)}
.btn-ghost:hover{background:var(--ink);color:#fff}
.btn-teal{background:var(--teal-dark);border-color:var(--teal-dark)}
.btn-teal:hover{background:var(--marker);border-color:var(--ink);color:var(--ink)}
.btn-row{display:flex;gap:.8rem;flex-wrap:wrap;align-items:center}
.btn-note{font-size:.85rem;color:var(--muted)}

/* ---------- token chips (signature) ---------- */
.tok-chip{
  font-family:var(--mono);font-size:.92em;
  background:#fff;border:1px solid #D9D4C4;border-radius:6px;
  padding:.08em .38em;white-space:nowrap;
}
.tok-hl{background:var(--marker);border-color:#E4C93A}
mark{background:var(--marker-soft);padding:.05em .15em;border-radius:3px}

/* ---------- hero ---------- */
.hero{padding:4.5rem 0 3.5rem;border-bottom:1px solid var(--rule)}
.hero-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:3rem;align-items:center}
.eyebrow{font-family:var(--mono);font-size:.8rem;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);margin-bottom:1rem}
h1{font-family:var(--serif);font-weight:500;font-size:clamp(2.1rem,4.6vw,3.4rem);line-height:1.12;letter-spacing:-.01em;margin-bottom:1.2rem}
.hero p.lede{font-size:1.2rem;color:var(--muted);max-width:34em;margin-bottom:1.8rem}

/* next-token demo */
.predict{
  font-family:var(--serif);font-size:clamp(1.4rem,2.6vw,1.9rem);line-height:1.4;margin:0 0 1.4rem;
}
.predict .slot{
  display:inline-block;min-width:5.2em;border-bottom:3px solid var(--ink);
  font-family:var(--mono);font-size:.85em;text-align:center;padding:0 .2em;
}
.predict .slot .fill{background:var(--marker);border-radius:4px;padding:.05em .25em}
.cands{list-style:none;display:grid;gap:.45rem;max-width:22rem}
.cands li{display:grid;grid-template-columns:auto 1fr auto;gap:.7rem;align-items:center;font-family:var(--mono);font-size:.9rem}
.cands .bar{height:9px;border-radius:5px;background:var(--teal);opacity:.85;transform-origin:left;transition:transform .6s ease}
.cands .pct{color:var(--muted);font-size:.8rem;min-width:3.2em;text-align:right}
.cands li.win .bar{background:var(--ink)}
.demo-caption{font-size:.85rem;color:var(--muted);margin-top:.9rem;max-width:26rem}

/* ---------- book cover (CSS-drawn placeholder) ---------- */
.cover{
  width:min(300px,80%);aspect-ratio:2/3;margin:0 auto;
  background:var(--ink);color:var(--paper);border-radius:6px 14px 14px 6px;
  box-shadow:12px 14px 0 rgba(28,36,49,.12);
  padding:1.6rem 1.4rem;display:flex;flex-direction:column;justify-content:space-between;
  position:relative;overflow:hidden;
}
.cover::before{content:"";position:absolute;left:10px;top:0;bottom:0;width:2px;background:rgba(255,255,255,.18)}
.cover .c-eyebrow{font-family:var(--mono);font-size:.62rem;letter-spacing:.18em;text-transform:uppercase;opacity:.7}
.cover .c-title{font-family:var(--serif);font-size:1.75rem;line-height:1.15;margin:.6rem 0}
.cover .c-title em{font-style:normal;background:var(--marker);color:var(--ink);padding:0 .18em;border-radius:3px}
.cover .c-sub{font-size:.8rem;opacity:.85;line-height:1.45}
.cover .c-author{font-family:var(--mono);font-size:.75rem;letter-spacing:.08em;opacity:.9}

/* ---------- sections ---------- */
section{padding:3.5rem 0}
section+section{border-top:1px solid var(--rule)}
h2{font-family:var(--serif);font-weight:500;font-size:clamp(1.6rem,3vw,2.2rem);line-height:1.2;margin-bottom:1rem;letter-spacing:-.01em}
h3{font-family:var(--serif);font-weight:600;font-size:1.3rem;margin:1.8rem 0 .6rem}
.section-intro{color:var(--muted);max-width:38em;margin-bottom:2rem}

.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:1.2rem}
.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:1.6rem}
.card{background:var(--card);border:1px solid var(--rule);border-radius:12px;padding:1.5rem}
.card h3{margin-top:0;font-size:1.15rem}
.card p{font-size:.97rem;color:var(--muted)}
.card .tok-chip{margin-bottom:.8rem;display:inline-block}

/* chapter list */
.chapters{list-style:none;counter-reset:ch;max-width:44rem}
.chapters li{
  counter-increment:ch;display:flex;gap:1.1rem;align-items:baseline;
  padding:1rem 0;border-bottom:1px solid var(--rule);
}
.chapters li::before{
  content:counter(ch,decimal-leading-zero);
  font-family:var(--mono);font-size:.85rem;color:var(--muted);min-width:2.2em;
}
.chapters strong{font-family:var(--serif);font-weight:600;font-size:1.1rem;display:block}
.chapters span{color:var(--muted);font-size:.95rem}

/* quote / testimonial */
.pull{
  border-left:4px solid var(--marker);padding:.4rem 0 .4rem 1.4rem;margin:2rem 0;
  font-family:var(--serif);font-size:1.25rem;line-height:1.5;
}
.pull cite{display:block;font-family:var(--mono);font-style:normal;font-size:.8rem;color:var(--muted);margin-top:.6rem}

/* FAQ */
.faq details{border-bottom:1px solid var(--rule);padding:1rem 0}
.faq summary{font-family:var(--serif);font-weight:600;font-size:1.15rem;cursor:pointer;list-style:none;display:flex;justify-content:space-between;gap:1rem}
.faq summary::after{content:"+";font-family:var(--mono);color:var(--muted)}
.faq details[open] summary::after{content:"–"}
.faq details p{margin-top:.7rem;color:var(--muted);max-width:44em}

/* CTA band */
.cta-band{background:var(--ink);color:var(--paper);border-radius:16px;padding:2.8rem 2.4rem;margin:1rem 0}
.cta-band h2{color:#fff}
.cta-band p{color:#C7CDD6;max-width:36em;margin-bottom:1.6rem}
.cta-band .btn{background:var(--marker);color:var(--ink);border-color:var(--marker)}
.cta-band .btn:hover{background:#fff;border-color:#fff}
.cta-band .btn-ghost{background:transparent;color:#fff;border-color:#fff}
.cta-band .btn-ghost:hover{background:#fff;color:var(--ink)}

/* ---------- article pages ---------- */
.article{max-width:44rem;margin:0 auto;padding:3.5rem 1.25rem}
.article h1{font-size:clamp(2rem,4vw,2.8rem)}
.article .meta{font-family:var(--mono);font-size:.8rem;color:var(--muted);margin-bottom:2.2rem}
.article p{margin:1.1rem 0}
.article h2{margin-top:2.6rem;font-size:1.7rem}
.article h3{font-size:1.25rem}
.article ul,.article ol{margin:1.1rem 0 1.1rem 1.4rem}
.article li{margin:.45rem 0}
.article .box{background:var(--card);border:1px solid var(--rule);border-left:4px solid var(--teal);border-radius:8px;padding:1.1rem 1.3rem;margin:1.6rem 0;font-size:.97rem}
.article .box strong{font-family:var(--mono);font-size:.8rem;letter-spacing:.08em;text-transform:uppercase;color:var(--teal-dark);display:block;margin-bottom:.4rem}
.article-cta{background:var(--card);border:1px solid var(--rule);border-radius:12px;padding:1.6rem;margin-top:3rem;display:grid;grid-template-columns:auto 1fr;gap:1.4rem;align-items:center}
.article-cta .mini-cover{width:76px;aspect-ratio:2/3;background:var(--ink);border-radius:3px 7px 7px 3px;flex-shrink:0;display:flex;align-items:center;justify-content:center;padding:.4rem}
.article-cta .mini-cover span{font-family:var(--serif);color:#fff;font-size:.55rem;text-align:center;line-height:1.3}
.article-cta p{margin:.3rem 0 .9rem;color:var(--muted);font-size:.95rem}
.article-cta h3{margin:0;font-size:1.1rem}

/* ---------- quiz ---------- */
.quiz-shell{max-width:44rem;margin:0 auto}
.quiz-card{background:var(--card);border:1px solid var(--rule);border-radius:14px;padding:2rem;margin:2rem 0}
.quiz-progress{font-family:var(--mono);font-size:.8rem;color:var(--muted);margin-bottom:1rem}
.quiz-q{font-family:var(--serif);font-size:1.4rem;line-height:1.35;margin-bottom:1.3rem}
.quiz-opts{display:grid;gap:.7rem}
.quiz-opts button{
  text-align:left;font-family:var(--sans);font-size:1rem;line-height:1.5;
  background:var(--paper);border:1.5px solid var(--rule);border-radius:10px;
  padding:.9rem 1.1rem;cursor:pointer;transition:border-color .12s,background .12s;color:var(--ink);
}
.quiz-opts button:hover{border-color:var(--ink)}
.quiz-opts button.correct{background:#E8F3EF;border-color:var(--teal)}
.quiz-opts button.wrong{background:#FBECEC;border-color:#C0564F}
.quiz-opts button:disabled{cursor:default}
.quiz-explain{margin-top:1.2rem;padding:1rem 1.2rem;background:var(--marker-soft);border-radius:10px;font-size:.97rem;display:none}
.quiz-explain.show{display:block}
.quiz-next{margin-top:1.3rem}
.quiz-result h2{margin-bottom:.4rem}
.score-big{font-family:var(--serif);font-size:4rem;line-height:1}
.score-label{font-family:var(--mono);font-size:.85rem;color:var(--muted);letter-spacing:.08em;text-transform:uppercase;margin-bottom:1.4rem}

/* ---------- footer ---------- */
.site-footer{border-top:1px solid var(--rule);margin-top:3rem;padding:2.5rem 0;font-size:.9rem;color:var(--muted)}
.site-footer .wrap{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:2rem}
.site-footer h4{font-family:var(--mono);font-size:.75rem;letter-spacing:.12em;text-transform:uppercase;margin-bottom:.8rem;color:var(--ink)}
.site-footer ul{list-style:none}
.site-footer li{margin:.4rem 0}
.site-footer a{color:var(--muted)}
.site-footer a:hover{color:var(--ink)}
.footnote{font-size:.8rem;margin-top:1.2rem}

/* ---------- responsive ---------- */
/* Tablets */
@media (max-width:1000px){
  .grid-3{grid-template-columns:1fr 1fr}
  .hero-grid{gap:2rem}
}
/* Small tablets & phones */
@media (max-width:820px){
  .hero-grid,.grid-2,.grid-3,.site-footer .wrap{grid-template-columns:1fr}
  .hero{padding:2.4rem 0 2.2rem}
  .hero p.lede{font-size:1.08rem}
  .predict{font-size:1.3rem}
  section{padding:2.4rem 0}
  .article{padding:2.4rem 1.25rem}
  .cover-img{margin-top:1.4rem}
  /* header: logo on top, nav becomes a swipeable strip that never overlaps */
  .site-header .wrap{flex-wrap:wrap;row-gap:.4rem}
  .nav{width:100%;flex-wrap:nowrap;overflow-x:auto;gap:1.1rem;padding-bottom:.35rem;-webkit-overflow-scrolling:touch;scrollbar-width:none}
  .nav::-webkit-scrollbar{display:none}
  .nav a{white-space:nowrap;flex-shrink:0}
  .cta-band{padding:1.8rem 1.3rem;border-radius:12px}
  .quiz-card{padding:1.4rem}
  .quiz-q{font-size:1.25rem}
  .score-big{font-size:3rem}
  .article-cta{grid-template-columns:1fr}
  .article-cta .mini-cover-img{display:none}
  .pull{font-size:1.1rem}
}
/* Small phones */
@media (max-width:400px){
  body{font-size:1rem}
  .btn{padding:.7rem 1.15rem;font-size:.95rem}
  .cands{max-width:100%}
}

/* ---------- fixes & real cover ---------- */
/* nav CTA button: .nav a was out-specifying .btn and inking the text */
.nav a.btn{color:#fff}
.nav a.btn:hover{color:var(--ink);text-decoration:none}

.cover-img{
  display:block;width:min(320px,85%);height:auto;margin:0 auto;
  border-radius:4px 10px 10px 4px;box-shadow:12px 14px 0 rgba(28,36,49,.12);
}
.mini-cover-img{width:76px;height:auto;border-radius:2px 5px 5px 2px;box-shadow:4px 5px 0 rgba(28,36,49,.12)}

.part-label{
  font-family:var(--mono);font-size:.78rem;letter-spacing:.14em;text-transform:uppercase;
  color:var(--muted);margin:2.2rem 0 .3rem;
}
.chapters+.part-label{margin-top:2.6rem}