.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.chapter{max-width:78rem;margin:0 auto;padding:1.25rem 1.25rem 5rem;color:var(--fg)}@media(min-width:768px){.chapter{padding:2.5rem 2rem 6rem}}@media(min-width:1100px){.chapter{padding:3rem 2.5rem 7rem}}.chap-head{margin:0 0 2.25rem}.chap-running{margin:0 0 .6rem;display:flex;flex-wrap:wrap;align-items:baseline;gap:.55rem;font-family:var(--font-mono);font-size:.7rem;text-transform:uppercase;letter-spacing:.18em;color:var(--muted)}.chap-running-tag{color:var(--accent);letter-spacing:.16em}.chap-running-dot{color:var(--border)}.chap-running-phase i{font-family:var(--font-serif);font-style:italic;font-size:.95rem;letter-spacing:.02em;text-transform:none;color:var(--accent);margin-left:.18em}.chap-running-spine .num{font-variant-numeric:tabular-nums;font-family:var(--font-mono);color:var(--fg)}.chap-running-slash{margin:0 .2em;color:var(--border)}.chap-progress{position:relative;margin:0 0 1.6rem;height:2px;background:var(--border);width:100%;overflow:hidden}.chap-progress-fill{display:block;height:100%;background:var(--accent)}.chap-title{margin:0;font-family:var(--font-display, var(--font-sans));font-weight:650;font-size:clamp(1.85rem,4vw,3rem);line-height:1.07;letter-spacing:-.005em;color:var(--fg);max-width:22ch}.chap-subtitle{margin:.8rem 0 0;font-family:var(--font-serif);font-style:italic;font-size:clamp(1.05rem,2vw,1.25rem);line-height:1.4;color:var(--muted);max-width:40ch}.chap-meta{margin:1.4rem 0 0;display:flex;flex-wrap:wrap;align-items:baseline;gap:.5rem .8rem;font-family:var(--font-mono);font-size:.72rem;color:var(--muted);letter-spacing:.04em}.chap-meta-phase{color:var(--fg);font-family:var(--font-sans);font-weight:600;text-transform:uppercase;letter-spacing:.18em;font-size:.68rem}.chap-meta-dot{color:var(--border)}.chap-meta-chip{display:inline-flex;align-items:baseline;gap:.32em}.chap-meta-chip .num{font-variant-numeric:tabular-nums;color:var(--fg)}.chap-meta-of{color:var(--border)}.chap-meta-label{color:var(--muted)}.chap-body{display:grid;grid-template-columns:minmax(0,1fr);gap:1.5rem}.chap-margin{display:flex;flex-direction:row;flex-wrap:wrap;gap:1.25rem 2rem;padding:1rem 0;border-top:1px solid var(--border);border-bottom:1px solid var(--border)}.chap-margin-block{min-width:0}.chap-margin-eyebrow{margin:0 0 .4rem;font-family:var(--font-mono);font-size:.62rem;text-transform:uppercase;letter-spacing:.22em;color:var(--muted)}.chap-margin-title{margin:0;font-family:var(--font-serif);font-style:italic;font-size:1rem;color:var(--fg);line-height:1.3}.chap-margin-stat{margin:0;font-family:var(--font-mono);font-size:1.05rem;color:var(--fg);display:inline-flex;align-items:baseline;gap:.3em;font-variant-numeric:tabular-nums}.chap-margin-unit{font-size:.72rem;color:var(--muted);text-transform:uppercase;letter-spacing:.16em}.chap-pioneer-list{margin:0;padding:0;list-style:none;display:grid;gap:.6rem}.chap-pioneer{display:grid;grid-template-columns:40px minmax(0,1fr);align-items:center;gap:.6rem;min-height:44px}.chap-pioneer-thumb{display:block;width:40px;height:40px;object-fit:cover;object-position:center top;border:1px solid var(--border);background:var(--surface);border-radius:4px}.chap-pioneer-thumb-empty{display:inline-flex;align-items:center;justify-content:center;color:var(--muted);font-family:var(--font-serif);font-style:italic;font-size:1.1rem}.chap-pioneer-name{font-family:var(--font-serif);font-size:.92rem;color:var(--fg);line-height:1.2}.chap-column{min-width:0}.chap-hero{margin:0 0 1.6rem}.chap-hero img{display:block;width:100%;height:auto;border:1px solid var(--border);background:var(--surface);border-radius:6px}.chap-hero-credit{margin:.5rem 0 0;font-family:var(--font-mono);font-size:.66rem;color:var(--muted);text-align:right;letter-spacing:.04em}.chap-lede{margin:0 0 1.8rem;max-width:32ch;font-family:var(--font-serif);font-size:clamp(1.3rem,3.4vw,1.85rem);line-height:1.22;color:var(--fg);letter-spacing:-.005em}.chap-lede em{color:var(--accent);font-style:italic}.chap-prose{max-width:70ch;font-family:var(--font-serif);font-size:1.05rem;line-height:1.7;color:var(--fg)}.chap-prose>*+*{margin-top:1.1rem}.chap-prose p{margin:0}.chap-prose p+p{margin-top:1.1rem}.chap-prose h2{margin:2.4rem 0 .6rem;font-family:var(--font-display, var(--font-sans));font-size:clamp(1.35rem,2.4vw,1.6rem);font-weight:600;line-height:1.2;color:var(--fg);letter-spacing:-.005em;display:flex;align-items:baseline;gap:.65rem}.chap-prose h2:before{content:"§";font-family:var(--font-serif);font-style:italic;color:var(--accent);font-size:.9em;font-weight:400}.chap-prose h3{margin:1.8rem 0 .4rem;font-family:var(--font-display, var(--font-sans));font-size:1.1rem;font-weight:600;color:var(--fg)}.chap-prose em{color:var(--accent);font-style:italic}.chap-prose strong{color:var(--fg);font-weight:600}.chap-prose a{color:var(--accent);text-decoration-thickness:1px;text-underline-offset:2px}.chap-prose code{font-family:var(--font-mono);font-size:.9em;padding:.08em .32em;background:var(--surface);border:1px solid var(--border);border-radius:3px;color:var(--fg)}.chap-prose pre{margin:1.4rem 0;padding:1rem 1.1rem;background:var(--surface);border:1px solid var(--border);border-radius:6px;overflow-x:auto;-webkit-overflow-scrolling:touch;font-family:var(--font-mono);font-size:.88rem;line-height:1.55}.chap-prose pre code{background:transparent;border:0;padding:0}.chap-prose blockquote{margin:1.5rem 0;padding-left:1.1rem;border-left:2px solid var(--accent);font-style:italic;color:var(--muted)}.chap-prose ul,.chap-prose ol{margin:0;padding-left:1.4rem}.chap-prose li+li{margin-top:.5rem}.chap-prose hr{margin:2.2rem auto;border:0;border-top:1px solid var(--border);width:8rem}.chap-prose img{display:block;max-width:100%;height:auto;margin:1.4rem auto;border:1px solid var(--border);border-radius:6px}.chap-prose figure{margin:1.6rem 0}.chap-prose figcaption{margin-top:.5rem;font-family:var(--font-mono);font-size:.72rem;color:var(--muted);letter-spacing:.02em;text-align:center}.chap-prose .katex-display{overflow-x:auto;overflow-y:hidden;-webkit-overflow-scrolling:touch;max-width:100%}@media(min-width:1024px){.chap-body{grid-template-columns:14rem minmax(0,1fr);gap:3rem;align-items:start}.chap-margin{flex-direction:column;gap:1.6rem;padding:0;border-top:0;border-bottom:0;border-right:1px solid var(--border);padding-right:1.5rem;position:sticky;top:1.5rem}.chap-margin-block{width:100%}}@media(min-width:1280px){.chap-body{grid-template-columns:15rem minmax(0,1fr);gap:4rem}}.num{font-family:var(--font-mono);font-variant-numeric:tabular-nums}.chap-prose .lesson-figure{margin:1.8rem 0;padding:1rem 1rem .85rem;border:1px solid var(--border);border-radius:6px;background:var(--surface-soft, var(--surface));color:var(--fg)}.chap-prose .lesson-figure svg{display:block;width:100%;height:auto;max-width:36rem;margin:0 auto;border-radius:4px}.chap-prose .lesson-figure figcaption{margin:.75rem auto 0;max-width:52ch;font-family:var(--font-serif);font-style:italic;font-size:.88rem;line-height:1.5;color:var(--muted);text-align:center;letter-spacing:0}.chap-back-row{margin:0 0 1.6rem}.chap-back{display:inline-flex;align-items:baseline;gap:.45rem;font-family:var(--font-mono);font-size:.72rem;text-transform:uppercase;letter-spacing:.18em;color:var(--muted);text-decoration:none;transition:color .14s ease;min-height:44px;padding:.6rem 0}.chap-back-arrow{display:inline-block;transition:transform .2s cubic-bezier(.2,.7,.2,1)}.chap-back:hover{color:var(--fg)}.chap-back:hover .chap-back-arrow{transform:translate(-3px)}.chap-nav{margin:3.5rem 0 0;padding-top:1.6rem;border-top:1px solid var(--border);display:grid;grid-template-columns:minmax(0,1fr);gap:.6rem;max-width:70ch}@media(min-width:640px){.chap-nav{grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:1rem}}.chap-nav-link{display:flex;flex-direction:column;gap:.4rem;padding:1rem 1.1rem;border:1px solid var(--border);border-radius:6px;background:var(--bg);color:var(--fg);text-decoration:none;min-height:64px;transition:border-color .14s ease,background .14s ease}.chap-nav-link:hover{border-color:var(--accent);background:var(--surface)}.chap-nav-link:focus-visible{outline:2px solid var(--accent);outline-offset:2px}.chap-nav-prev{text-align:left}.chap-nav-next{text-align:right}.chap-nav-next .chap-nav-eyebrow{justify-content:flex-end}.chap-nav-eyebrow{display:inline-flex;align-items:baseline;gap:.4rem;font-family:var(--font-mono);font-size:.66rem;text-transform:uppercase;letter-spacing:.2em;color:var(--muted)}.chap-nav-arrow{display:inline-block;color:var(--accent);transition:transform .2s cubic-bezier(.2,.7,.2,1)}.chap-nav-link:hover .chap-nav-prev .chap-nav-arrow,.chap-nav-prev:hover .chap-nav-arrow{transform:translate(-3px)}.chap-nav-next:hover .chap-nav-arrow{transform:translate(3px)}.chap-nav-title{font-family:var(--font-serif);font-size:1.02rem;line-height:1.3;color:var(--fg)}.chap-nav-hub .chap-nav-title{color:var(--muted);font-style:italic}