/* Self-contained typography and surfaces: works offline, without font services. */
:root{color-scheme:light;--bg:#f7f6ef;--surface:#fffef8;--ink:#1f342d;--muted:#53665c;--line:#ccd3c5;--accent:#315d43;--soft:#e8eddf;--orange:#9e431f;--code:#1a2e27;--code-text:#eaf2df;--button:#fffef8;--shadow:0 18px 55px #233c2410}

body.dark{color-scheme:dark;--bg:#14231d;--surface:#1c2e25;--ink:#eef2e6;--muted:#bdcbbd;--line:#465b4a;--accent:#bed99f;--soft:#293e2e;--orange:#ffb58f;--code:#0f1c17;--code-text:#edf3e5;--button:#18271d;--shadow:none}

*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:6rem}
body{margin:0;background:var(--bg);color:var(--ink);font:17px/1.7 system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}
a{color:var(--accent);text-underline-offset:4px}
a:hover{text-decoration-thickness:2px}
button,input,textarea{font:inherit}
button,.button{cursor:pointer}
button{padding:.6rem .9rem;border:1px solid var(--line);border-radius:5px;color:var(--ink);background:var(--surface)}
button:hover{background:var(--soft)}
:focus-visible{outline:3px solid var(--orange);outline-offset:4px}
[hidden]{display:none!important}
h1,h2,h3,h4,p{margin:0 0 1rem}
h1,h2,h3,h4{line-height:1.14;letter-spacing:-.035em}
h1{font-size:clamp(2.8rem,5.7vw,5.6rem);font-weight:640;max-width:1000px}
h2{font-size:clamp(1.65rem,3vw,2.6rem);font-weight:620}
h3{font-size:1.25rem;line-height:1.3}
h4{font-size:1.2rem;line-height:1.4}
p{max-width:76ch}
em{font-style:normal;color:var(--accent)}
.skip{position:fixed;top:-100px;left:1rem;z-index:100;background:var(--surface);padding:1rem}
.skip:focus{top:1rem}
.top{border-bottom:1px solid var(--line);display:flex;justify-content:space-between;align-items:center;gap:1.3rem;padding:1rem clamp(1rem,4vw,4rem);background:var(--bg);position:sticky;top:0;z-index:10}
.brand{text-decoration:none;font-weight:850;font-size:1.2rem;letter-spacing:-.04em;color:var(--ink)}
.brand span{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:.65rem;letter-spacing:.08em;font-weight:600;margin-left:.7rem}
.top nav{display:flex;align-items:center;gap:1.3rem;font-size:.8rem}
.top nav a{text-decoration:none}
.top button{font-size:.75rem;padding:.35rem .7rem}
.eyebrow,.tag,.topic,.card-top,.card-bottom,.case-number{font-family:ui-monospace,SFMono-Regular,Consolas,monospace}
.eyebrow{text-transform:uppercase;letter-spacing:.12em;font-size:.68rem;font-weight:700;color:var(--orange);margin-bottom:1.3rem}
.subtitle{font-size:clamp(1.1rem,2vw,1.4rem);line-height:1.5;color:var(--muted);max-width:52ch}
.topic{font-size:.77rem;color:var(--muted);margin-top:1.5rem}
.actions{display:flex;flex-wrap:wrap;align-items:center;gap:.8rem;margin:1.6rem 0}
.button{display:inline-flex;gap:1rem;align-items:center;justify-content:space-between;padding:.85rem 1.15rem;background:var(--accent);color:var(--button);border:1px solid var(--accent);border-radius:5px;text-decoration:none;font-size:.86rem;font-weight:650}
.button:hover{filter:brightness(.95)}
.button.secondary{background:transparent;color:var(--accent);border-color:var(--line)}
.overview{max-width:1500px;margin:auto;padding:0 clamp(1.2rem,5vw,5rem)}
.overview-hero{display:grid;grid-template-columns:1.6fr 1fr;gap:5rem;align-items:center;padding:6rem 0 5rem}
.overview-hero h1{font-size:clamp(2.8rem,5.4vw,5.2rem)}
.hero-note{border:1px solid var(--line);border-top:5px solid var(--accent);padding:2.2rem;background:var(--soft);transform:rotate(1deg);box-shadow:var(--shadow)}
.hero-note h2{font-size:1.9rem;margin-top:1.4rem}
.hero-note p{color:var(--muted);font-size:.95rem}
.cycle{display:grid;grid-template-columns:1fr 1fr;gap:0;border:1px solid var(--line);margin-top:1.7rem;font: .76rem/1.6 ui-monospace,monospace}
.cycle span{padding:1rem;border:1px solid var(--line)}
.intro-grid{display:grid;grid-template-columns:repeat(3,1fr);border-top:1px solid var(--line);border-bottom:1px solid var(--line);gap:2.5rem;padding:2.5rem 0;margin-bottom:5rem}
.intro-grid h2{font-size:1.4rem}
.intro-grid p{font-size:.94rem;color:var(--muted);margin:0}
.intro-grid .eyebrow{display:block;margin-bottom:1rem}
.section-heading{display:flex;gap:2rem;align-items:end;justify-content:space-between;margin-bottom:2rem}
.section-heading h2{max-width:650px;margin:0}
.section-heading>p{font-size:.8rem;color:var(--muted);max-width:240px}
.journey-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:1rem}
.journey-card{display:flex;flex-direction:column;gap:1rem;text-decoration:none;color:var(--ink);border:1px solid var(--line);background:var(--surface);border-radius:6px;padding:1.7rem;transition:transform .15s,border-color .15s}
.journey-card:hover{transform:translateY(-3px);border-color:var(--accent)}
.card-top{display:flex;justify-content:space-between;font-size:.75rem;color:var(--orange)}
.card-top span{color:var(--muted)}
.journey-card h3{font-size:1.6rem;margin:.4rem 0 0}
.journey-card p{font-size:.93rem;color:var(--muted);margin:0 0 1rem}
.card-bottom{display:flex;justify-content:space-between;font-size:.65rem;margin-top:auto;color:var(--accent);border-top:1px solid var(--line);padding-top:1rem}
.closing{padding:5rem 0;max-width:850px}
.closing p{color:var(--muted)}
.week-nav{max-width:1330px;margin:0 auto;display:flex;gap:.45rem;padding:1.2rem 2rem;flex-wrap:wrap;border-bottom:1px solid var(--line)}
.week-nav a{font: .73rem/1.5 ui-monospace,monospace;text-decoration:none;padding:.5rem .65rem;border:1px solid transparent;border-radius:4px}
.week-nav a[aria-current]{background:var(--accent);color:var(--button)}
.week-nav a:hover{border-color:var(--line)}
.lesson-layout{max-width:1330px;margin:auto;display:grid;grid-template-columns:220px minmax(0,1fr);gap:4rem;padding:0 2rem}
.rail{align-self:start;position:sticky;top:7rem;padding-top:4rem;font-size:.78rem}
.rail a{display:block;padding:.6rem 0;text-decoration:none;color:var(--muted)}
.rail a:hover{color:var(--accent)}
.rail p:last-child{margin-top:2rem;border-top:1px solid var(--line);padding-top:1.4rem;color:var(--muted)}
.lesson-content{min-width:0}
.hero{padding:4rem 0 3rem;border-bottom:1px solid var(--line)}
.hero h1{font-size:clamp(2.5rem,4.7vw,4.7rem)}
.section{padding:3.7rem 0;border-bottom:1px solid var(--line)}
.section .lead{font-size:1.18rem}
.mission{border-left:4px solid var(--accent);padding:1.5rem 1.7rem;margin:2rem 0;background:var(--soft)}
.mission p{margin:.8rem 0 0}
.tag{font-size:.7rem;color:var(--accent);font-weight:700;letter-spacing:.035em}
.note{font-size:.86rem;color:var(--muted);line-height:1.65}
.concepts{display:grid;gap:1.3rem;margin:2rem 0}
.concepts article{padding-left:1.3rem;border-left:1px solid var(--line)}
.concepts p{font-size:1rem;color:var(--muted);margin:0}
details{border:1px solid var(--line);border-radius:6px;background:var(--surface);margin:1rem 0}
summary{cursor:pointer;font-weight:650;padding:1.1rem 1.2rem;line-height:1.5}
summary::marker{color:var(--accent)}
details>p,details>h3,details>.note{margin:1rem 1.2rem}
pre{background:var(--code);color:var(--code-text);padding:1.4rem;overflow:auto;border-radius:4px;font: .84rem/1.75 ui-monospace,SFMono-Regular,Consolas,monospace;margin:1rem;tab-size:4}
label{display:block;font-size:.86rem;font-weight:650;margin:1.5rem 0 .6rem}
textarea{display:block;width:100%;resize:vertical;border:1px solid var(--line);border-radius:5px;background:var(--surface);color:var(--ink);padding:1rem;font-size:.95rem;line-height:1.6}
textarea::placeholder{color:var(--muted)}
.bench-case{margin:1rem 0}
.case-number{color:var(--orange);font-size:.75rem;margin-right:1rem}
.case-body{padding:0 1.3rem 1.3rem}
.case-input{font: .88rem/1.7 ui-monospace,monospace;padding:1rem;background:var(--soft);border-radius:4px}
.advance{margin:.5rem 0 1rem}
.trace{padding-left:1.7rem;font-size:.94rem}
.trace li{padding:.5rem 0 .5rem .5rem}
.case-result{background:var(--soft);padding:1.3rem;border-left:3px solid var(--accent);margin-top:1rem}
.case-result h4{margin-bottom:.6rem}
.case-result p{margin:0;font-size:.94rem}
.simulator{margin-top:2rem;border:1px solid var(--accent);border-radius:6px;padding:1.6rem}
.simulator p{font-size:.9rem}
.simulator input[type=range]{display:block;width:100%;accent-color:var(--accent);margin:1rem 0 1.5rem}
.simulator output{display:block;font:600 1rem/1.7 ui-monospace,monospace;padding:1rem;background:var(--soft);margin:1.2rem 0}
.sample-strip{display:flex;gap:.5rem;flex-wrap:wrap;margin:1.2rem 0}
.sample-strip span{font: .68rem/1.5 ui-monospace,monospace;border:1px solid var(--line);padding:.6rem;text-align:center;border-radius:4px}
.sample-strip .high{border-color:var(--orange);color:var(--orange);font-weight:800}
.investigation{counter-reset:steps;list-style:none;padding:0;margin:2rem 0}
.investigation li{counter-increment:steps;position:relative;padding:.2rem 0 1.5rem 3rem}
.investigation li:before{content:counter(steps,decimal-leading-zero);position:absolute;left:0;top:.2rem;font: .8rem/1.8 ui-monospace,monospace;color:var(--orange)}
.practice{list-style:none;padding:0}
.practice li{padding:.8rem 0;border-bottom:1px solid var(--line);font-size:.9rem}
.practice .tag{margin-right:1rem}
.ai-review{background:var(--soft);padding:2rem;margin-top:2rem;border:1px solid var(--line);border-radius:6px}
.notebook-tools{margin:1rem 0}
.notebook-tools p{font-size:.8rem;color:var(--muted);margin-top:.7rem}
.next-idea{margin-top:2rem;font-size:1rem;color:var(--accent)}
.prev-next{display:flex;justify-content:space-between;gap:1rem;padding:2rem 0;font-size:.85rem}
footer{border-top:1px solid var(--line);padding:2rem clamp(1.2rem,5vw,5rem);font-size:.76rem;color:var(--muted)}
footer p{margin-bottom:.5rem}

@media(max-width:1050px){.overview-hero{gap:2rem}
.journey-grid{grid-template-columns:repeat(2,1fr)}
.lesson-layout{grid-template-columns:170px minmax(0,1fr);gap:2rem}
.hero-note{padding:1.4rem}
.hero-note h2{font-size:1.5rem}
.intro-grid{gap:1.5rem}
}

@media(max-width:760px){.brand span{display:none}
.top{padding:.8rem 1rem;position:relative}
.top nav{gap:.8rem;font-size:.75rem}
.overview-hero{grid-template-columns:1fr;padding:3rem 0;gap:2rem}
.hero-note{transform:none}
.intro-grid{grid-template-columns:1fr;gap:2rem;margin-bottom:3rem}
.journey-grid{grid-template-columns:1fr}
.section-heading{display:block}
.section-heading>p{max-width:none;margin-top:1rem}
.journey-card{padding:1.4rem}
.lesson-layout{display:block;padding:0 1.2rem}
.rail{display:none}
.week-nav{padding:1rem;gap:.15rem}
.week-nav a{padding:.4rem .55rem}
.hero{padding:2.5rem 0 2rem}
.section{padding:2.5rem 0}
.ai-review{padding:1.4rem}
.case-body{padding:0 1rem 1rem}
.mission{padding:1.2rem}
.closing{padding:3rem 0}
.button{font-size:.8rem}
.actions{gap:.6rem}
.overview-hero h1{font-size:clamp(2.5rem,9vw,4rem)}
pre{margin:.7rem;padding:1rem;font-size:.76rem}
.prev-next{font-size:.8rem}
}

@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}
.journey-card{transition:none}
.journey-card:hover{transform:none}
}

@media print{body,body.dark{--bg:white;--surface:white;--ink:#111;--muted:#333;--line:#aaa;--accent:#234a32;--soft:#f2f2f2;--orange:#743719;--code:#f2f2f2;--code-text:#111;color-scheme:light;font-size:11pt}
.top,.rail,.week-nav,.actions,.advance,.notebook-tools,.prev-next,.simulator input,footer,.skip{display:none!important}
.lesson-layout{display:block;padding:0}
.section,.hero{padding:1.3rem 0}
.overview-hero,.intro-grid{display:block}
.hero-note{transform:none}
.journey-grid{grid-template-columns:1fr 1fr}
h1{font-size:30pt!important}
h2{font-size:20pt}
pre{white-space:pre-wrap;overflow-wrap:anywhere}
textarea{min-height:5rem}
.trace li[hidden],.case-result[hidden]{display:block!important}
details{break-inside:avoid}
.trace{break-inside:avoid}
.overview{padding:0}
}


.signal-plot{display:block;width:100%;height:auto;margin:1rem 0;overflow:visible}
.signal-plot text{fill:var(--muted);font:11px ui-monospace,monospace}
.signal-plot .axis{fill:none;stroke:var(--line)}
.signal-plot .signal{fill:none;stroke:var(--accent);stroke-width:2}
.signal-plot circle{fill:var(--orange);stroke:var(--surface);stroke-width:1.5}
.thermal-map{border-collapse:collapse;width:100%;table-layout:fixed;text-align:center;margin:1rem 0 1.5rem}
.thermal-map caption{font-size:.8rem;color:var(--muted);text-align:left;margin:.5rem 0}
.thermal-map th,.thermal-map td{border:1px solid var(--line);padding:.8rem .3rem;font-size:.9rem}
.thermal-map th{font-size:.72rem}
.thermal-map td{background:var(--soft)}
.thermal-map .hot{background:var(--orange);color:var(--bg);font-weight:750}
.thermal-map small{display:block;font-size:.65rem}


/* One column, one lesson step; course navigation stays compact. */
.lesson-layout{display:block;max-width:900px;padding:0 1.2rem}
#main>.path-picker{max-width:862px;margin:1rem auto;padding:0 1.2rem}
.hero{padding:1.5rem 0 1rem;border:0}
.hero h1{font-size:clamp(2rem,4vw,3rem)}
.hero .subtitle{font-size:1.1rem;margin-bottom:.5rem}
.hero .topic{margin:.5rem 0}
.section{padding:1.6rem 0}
.section>.eyebrow{display:none}
.section h2{font-size:clamp(1.4rem,3vw,1.9rem)}
.section .lead{font-size:1.05rem}
.mission{margin:1.3rem 0;padding:1rem 1.3rem}
.ai-review{margin:0;border:0;padding:0;background:transparent}
.top .path-menu{border:0;background:transparent;margin:0}
.top .path-menu summary{font-size:.8rem;font-weight:400;padding:.35rem}
.top .path-menu>div{background:var(--surface);color:var(--ink)}
.path-picker select{background:var(--surface);color:var(--ink)}
@media(max-width:760px){.top nav{gap:.5rem}.top .brand span{display:none}.hero{padding:1rem 0}.section{padding:1.2rem 0}}

/* Weekly openings: a short problem before terminology or logistics. */
.weekly-opening .connection{color:var(--muted);font-size:.96rem;max-width:68ch}
.first-task{border-left:3px solid var(--accent);background:var(--soft);padding:1.5rem;margin:1.7rem 0}
.first-task .eyebrow{margin-bottom:.6rem}
.first-task h2{font-size:1.55rem;margin-bottom:.7rem}
.first-task p:last-child{margin-bottom:0}
.opening-outcome{border-top:1px solid var(--line);padding-top:1rem;color:var(--muted)}

/* One continuous lesson; writing is an optional resource, not a learning stage. */
.lesson-notes{padding:1.25rem 0}
.lesson-notes textarea{margin-bottom:1.2rem}
.lesson-discussion .lead{font-size:1.1rem}
.legacy-anchor{display:block;scroll-margin-top:5rem}