/* Bootstrapping the Yield Curve — shared styles */

:root{
  --ink:#1b2a26;
  --ink-soft:#4d6b62;
  --paper:#f1ede2;
  --white:#fbf8f0;
  --coral:#b8862b;
  --coral-dark:#7d5a12;
  --aqua:#4f8a7b;
  --mint:#79b8a6;
  --line:rgba(27,42,38,.18);
  --line-soft:rgba(27,42,38,.11);
  --s1:#c4452c;
  --s2:#008878;
  --s3:#a8761a;
  --mono:'DM Mono',ui-monospace,monospace;
  --display:'Fraunces',Georgia,serif;
  --body:'Manrope',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
}

.skip{
  position:absolute;left:14px;top:-46px;z-index:99;
  padding:11px 16px;background:var(--ink);color:var(--white);
  font:600 13px var(--body);border-radius:2px;transition:top .15s ease;
}
.skip:focus{top:14px;outline:2px solid var(--coral);outline-offset:2px}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--paper);color:var(--ink);
  font-family:var(--body);font-size:16px;line-height:1.68;
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;text-decoration:none}
button{font:inherit}
img{max-width:100%}
h1,h2,h3,h4,p,ul,ol{margin-top:0}
.shell{width:min(1120px,calc(100% - 80px));margin-inline:auto}
.prose{width:min(1120px,calc(100% - 80px));margin-inline:auto}
.prose>p,.prose>h2,.prose>h3,.prose>ul,.prose>ol,.prose>.note,.prose>.standfirst,.prose>.eyebrow{max-width:64ch}
.prose>.eq,.prose>.callout,.prose>pre,.prose>.pager{max-width:880px}
.prose>figure,.prose>.tablewrap,.prose>.chart-card{max-width:none}

/* ---------- header ---------- */
.site-header{
  height:82px;display:flex;align-items:center;justify-content:space-between;
  width:min(1280px,calc(100% - 80px));margin:auto;border-bottom:1px solid var(--line);
}
.wordmark{display:inline-flex;align-items:center;gap:10px;font:500 12px var(--mono);letter-spacing:.05em}
.wordmark-mark{
  display:grid;place-items:center;width:30px;height:30px;
  border:1px solid var(--ink);border-radius:50%;font:650 16px var(--display);
}
.top-nav{display:flex;align-items:center;gap:30px;font-size:13px;color:var(--ink-soft)}
.top-nav a:hover{color:var(--coral-dark)}
.top-nav a[aria-current="page"]{color:var(--ink)}
.nav-cta{color:var(--ink);border-bottom:1px solid var(--ink);padding-bottom:4px}

/* ---------- chapter rail ---------- */
.rail{border-bottom:1px solid var(--line);background:var(--white)}
.rail-inner{
  width:min(1280px,calc(100% - 80px));margin:auto;display:flex;gap:0;
  overflow-x:auto;scrollbar-width:none;
}
.rail-inner::-webkit-scrollbar{display:none}
.rail a{
  flex:1 0 auto;min-width:150px;padding:15px 18px 14px;
  border-right:1px solid var(--line-soft);display:block;
}
.rail a:last-child{border-right:0}
.rail a:hover{background:#f7f3e8}
.rail .n{font:400 10px var(--mono);letter-spacing:.09em;color:var(--ink-soft)}
.rail .t{margin-top:4px;font-size:13px;line-height:1.35;color:var(--ink-soft)}
.rail a[aria-current="page"]{background:var(--ink)}
.rail a[aria-current="page"] .n{color:var(--mint)}
.rail a[aria-current="page"] .t{color:var(--paper)}

/* ---------- page hero ---------- */
.page-hero{padding:58px 0 36px}
.eyebrow{margin:0 0 20px;color:var(--coral-dark);font:500 11px var(--mono);letter-spacing:.08em}
.eyebrow-dot{display:inline-block;width:7px;height:7px;margin-right:8px;border-radius:50%;background:var(--coral)}
h1{
  font-family:var(--display);font-weight:500;line-height:.99;letter-spacing:-.005em;
  font-size:clamp(46px,6.4vw,82px);max-width:15ch;margin-bottom:26px;
}
h1 em,h2 em,.standfirst em{color:var(--coral);font-style:italic}
.standfirst{max-width:46ch;color:var(--ink-soft);font-size:19px;line-height:1.55;margin-bottom:0}

/* home hero split */
.hero-split{display:grid;grid-template-columns:1.02fr .98fr;gap:66px;align-items:center;padding:58px 0 66px}
.hero-visual{
  position:relative;min-height:420px;overflow:hidden;
  background:var(--ink);color:var(--paper);border-radius:2px;
}
.visual-label{position:absolute;top:26px;left:28px;z-index:2;color:#a8bdb6;font:10px var(--mono);letter-spacing:.08em}
.hero-chart{position:absolute;inset:66px 24px 52px 24px;width:calc(100% - 48px);height:calc(100% - 118px)}
.chart-grid{fill:none;stroke:rgba(245,242,234,.16);stroke-width:1}
.curve{fill:none;stroke-width:2.5}
.curve-point{fill:var(--coral);stroke:var(--ink);stroke-width:3}
.visual-axis{position:absolute;color:#a8bdb6;font:10px var(--mono)}
.axis-x{right:26px;bottom:22px;left:26px;display:flex;justify-content:space-between}

.orbit{position:absolute;border:1px solid rgba(184,134,43,.40);border-radius:50%;transform:rotate(-17deg);pointer-events:none}
.orbit-a{width:490px;height:176px;right:-170px;bottom:24px}
.orbit-b{width:410px;height:148px;right:-100px;bottom:76px;border-color:rgba(79,138,123,.34)}
.visual-caption{position:absolute;right:28px;top:24px;text-align:right;color:#a8bdb6;font:11px var(--mono);line-height:1.45}
.visual-caption strong{color:var(--paper);font-weight:400}

.hero-actions{display:flex;align-items:center;gap:20px;margin-top:34px;flex-wrap:wrap}
.button{display:inline-flex;align-items:center;gap:20px;padding:15px 19px;font-size:13px;font-weight:700;transition:transform .2s ease}
.button:hover{transform:translateY(-3px)}
.button-dark{background:var(--ink);color:var(--white)}
.button-line{border:1px solid var(--ink)}

/* ---------- facts strip ---------- */
.facts{
  display:grid;grid-template-columns:repeat(4,1fr);gap:24px;
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);
  padding:24px max(40px,calc((100% - 1120px)/2));
}
.facts div{display:flex;align-items:baseline;gap:11px;color:var(--ink-soft);font:10px var(--mono);text-transform:uppercase;line-height:1.5}
.facts b{color:var(--ink);font:650 25px var(--display)}

.section-head{
  display:grid;grid-template-columns:.92fr 1.08fr;gap:60px;align-items:end;
  margin:56px 0 28px;padding-bottom:22px;border-bottom:1px solid var(--line);
}
.section-head h2{margin:0}
.section-head .intro{margin:0 0 3px;color:var(--ink-soft);font-size:15.5px;line-height:1.6;max-width:48ch}
@media (max-width:900px){.section-head{display:block;margin:40px 0 22px}.section-head .intro{margin-top:16px}}

/* ---------- prose ---------- */
.body-copy{padding:4px 0 8px}
h2{
  font-family:var(--display);font-weight:500;letter-spacing:-.005em;line-height:1.06;
  font-size:clamp(28px,3.2vw,36px);margin:48px 0 16px;
}
h3{font-family:var(--body);font-weight:700;font-size:15px;margin:34px 0 8px}
p{margin-bottom:20px}
ul,ol{margin-bottom:20px;padding-left:22px}
li{margin-bottom:8px}
.body-copy a:not(.button){border-bottom:1px solid var(--coral);color:var(--coral-dark)}
.body-copy a:not(.button):hover{background:rgba(184,134,43,.13)}
strong{font-weight:700}
.rule{height:1px;background:var(--line);margin:34px 0 0}

code{font-family:var(--mono);font-size:.87em;background:rgba(27,42,38,.07);padding:.1em .36em;border-radius:3px}
pre{
  background:var(--ink);color:#e7eee9;border-radius:2px;
  padding:20px 22px;overflow-x:auto;font-family:var(--mono);font-size:12.5px;line-height:1.65;
  margin:0 0 24px;
}
pre code{background:none;padding:0;font-size:inherit}
.cmt{color:#8aa79d}

/* ---------- equation card ---------- */
.eq{position:relative;margin:32px 0;padding:30px 28px 24px;background:var(--white);border:1px solid var(--line)}
.eq-tag{
  position:absolute;top:-8px;left:22px;padding:1px 9px;background:var(--white);border:1px solid var(--line);
  font:10px var(--mono);letter-spacing:.09em;text-transform:uppercase;color:var(--coral-dark);
}
.eq-body{overflow-x:auto;overflow-y:hidden;text-align:center;padding:6px 0}
.eq-note{margin:18px 0 0;font-size:13.5px;line-height:1.6;color:var(--ink-soft)}

/* ---------- note / callout ---------- */
.note{border-left:2px solid var(--coral);padding:3px 0 3px 18px;margin:28px 0;font-size:14.5px;line-height:1.62;color:var(--ink-soft)}
.note b{color:var(--ink);font-weight:700}
.callout{background:var(--ink);color:#dde7e2;padding:30px 32px;margin:38px 0}
.callout .k{font:10px var(--mono);letter-spacing:.1em;text-transform:uppercase;color:var(--mint);margin:0 0 12px}
.callout p{margin:0;font-size:16.5px;line-height:1.6}
.callout strong{color:#fff}
.callout em{color:var(--mint);font-style:italic}

/* ---------- tables ---------- */
.tablewrap{overflow-x:auto;border:1px solid var(--line);background:var(--white);margin:0 0 24px}
table{border-collapse:collapse;width:100%;font-family:var(--mono);font-size:12.5px}
th,td{padding:9px 13px;border-bottom:1px solid var(--line-soft);text-align:right;white-space:nowrap}
th:first-child,td:first-child{text-align:left}
thead th{font-size:10px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink-soft);font-weight:400}
tbody tr:last-child td{border-bottom:0}
caption{caption-side:bottom;padding:11px 13px;text-align:left;font-family:var(--body);font-size:12.5px;color:var(--ink-soft)}

/* ---------- figures ---------- */
figure{margin:32px 0}
figure .frame{background:var(--white);border:1px solid var(--line);padding:14px}
figure img{display:block}
figcaption{margin-top:11px;font-size:12.5px;color:var(--ink-soft)}

/* ---------- chart ---------- */
.chart-card{background:var(--white);border:1px solid var(--line);padding:22px 24px 18px;margin:28px 0;position:relative}
.chart-head{display:flex;justify-content:space-between;align-items:center;gap:14px;flex-wrap:wrap;margin-bottom:8px}
.chart-title{font-size:13px;font-weight:700}
.legend{display:flex;gap:15px;font:11px var(--mono);color:var(--ink-soft)}
.legend span{display:inline-flex;align-items:center;gap:6px}
.legend i{width:16px;height:3px;border-radius:2px}
#chart{display:block;width:100%;height:340px;overflow:visible;touch-action:none}
.gridline{stroke:var(--line-soft);stroke-width:1}
.axis-text{fill:var(--ink-soft);font:10px var(--mono)}
.series-line{fill:none;stroke-width:2}
.series-dot{stroke:var(--white);stroke-width:2}
.crosshair{stroke:var(--ink);stroke-width:1;stroke-dasharray:3 3;opacity:0}
.dlabel{font:500 11px var(--mono)}
#tip{
  position:absolute;pointer-events:none;opacity:0;transition:opacity .12s;
  background:var(--ink);color:#fff;padding:9px 11px;font:11px var(--mono);
  line-height:1.55;white-space:nowrap;z-index:5;
}
.switch{display:flex;margin-bottom:16px;border:1px solid var(--ink);width:fit-content}
.switch button{font-size:12.5px;font-weight:600;padding:8px 17px;background:transparent;border:0;cursor:pointer;color:var(--ink-soft)}
.switch button+button{border-left:1px solid var(--ink)}
.switch button.active{background:var(--ink);color:var(--white)}

/* ---------- chapter cards ---------- */
.ch-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-top:8px}
.ch-card{display:flex;flex-direction:column;min-height:250px;padding:25px;border:1px solid var(--line);background:var(--white)}
.ch-card:hover{border-color:var(--ink)}
.ch-card.featured{background:#9c6d16;color:#fff;border-color:#9c6d16;transform:translateY(-12px)}
.ch-card .n{font:11px var(--mono);color:var(--coral-dark)}
.ch-card.featured .n,.ch-card.featured .go,.ch-card.featured h3,.ch-card.featured p{color:#fff}
.ch-card h3{font-family:var(--display);font-weight:500;font-size:25px;line-height:1.06;margin:40px 0 12px;color:inherit}
.ch-card p{font-size:13.5px;line-height:1.55;color:var(--ink-soft);margin-bottom:16px}

.ch-card .go{margin-top:auto;font:10px var(--mono);letter-spacing:.06em;text-transform:uppercase;color:var(--coral-dark)}

/* ---------- pager ---------- */
.pager{display:grid;grid-template-columns:1fr 1fr;gap:14px;margin:80px 0 0}
.pager a{padding:22px 24px;border:1px solid var(--line);background:var(--white);display:block}
.pager a:hover{border-color:var(--ink)}
.pager .dir{font:10px var(--mono);letter-spacing:.08em;text-transform:uppercase;color:var(--ink-soft)}
.pager .t{font-family:var(--display);font-size:21px;font-weight:500;margin-top:7px;letter-spacing:-.005em}
.pager .next{text-align:right}
.pager .empty{border:0;background:transparent}

/* ---------- footer ---------- */
.site-footer{background:var(--ink);color:#a8bdb6;margin-top:72px;padding:58px 0 38px}
.footer-grid{
  display:grid;grid-template-columns:1.5fr 1fr 1fr;gap:52px;
  padding-bottom:38px;border-bottom:1px solid rgba(255,253,248,.16);
}
.footer-brand .wordmark-mark{border-color:rgba(255,253,248,.55);color:var(--paper)}
.footer-brand .wordmark{color:var(--paper)}
.footer-blurb{margin:20px 0 0;max-width:34ch;font-size:14px;line-height:1.6;color:#a8bdb6}
.footer-by{margin:18px 0 0;font:11px var(--mono);letter-spacing:.04em;color:#7d968c}
.footer-by a{color:var(--paper);border-bottom:1px solid rgba(255,253,248,.34);padding-bottom:2px}
.footer-by a:hover{color:var(--mint);border-bottom-color:var(--mint)}
.footer-col h4{font:10px var(--mono);letter-spacing:.1em;text-transform:uppercase;color:var(--mint);margin:6px 0 15px;font-weight:400}
.footer-col ul{list-style:none;margin:0;padding:0}
.footer-col li{margin-bottom:9px}
.footer-col a{font-size:13.5px;color:#c8d6d0}
.footer-col a:hover{color:var(--coral)}
.footer-bottom{
  display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap;
  padding-top:24px;font:10px var(--mono);letter-spacing:.05em;color:#7d968c;
}
.footer-bottom a{color:#a8bdb6}
.footer-bottom a:hover{color:var(--coral)}

.reveal{animation:rise .8s both}
.reveal-delay{animation-delay:.15s}
@keyframes rise{from{opacity:0;transform:translateY(18px)}to{opacity:1;transform:translateY(0)}}
@media (prefers-reduced-motion:reduce){.reveal{animation:none}.button:hover,.ch-card.featured{transform:none}}

/* ---------- mobile ---------- */
@media (max-width:900px){
  body{font-size:15.5px}
  .shell,.prose,.site-header{width:min(100% - 38px,640px)}
  .site-header{height:68px}
  .top-nav{gap:15px;font-size:12px}
  .top-nav>a:not(.nav-cta):not(.nav-keep){display:none}
  .rail-inner{width:calc(100% - 20px)}
  .rail a{min-width:132px;padding:12px 14px}
  .page-hero{padding:44px 0 30px}
  h1{font-size:clamp(38px,10vw,52px)}
  .standfirst{font-size:17px}
  .hero-split{display:block;padding:44px 0 54px}
  .hero-visual{min-height:310px;margin-top:44px}
  .facts{grid-template-columns:repeat(2,1fr);padding:20px 19px;gap:16px}
  h2{margin-top:46px}
  .eq{padding:24px 17px 19px}
  .callout{padding:24px 20px}
  .ch-grid{grid-template-columns:1fr}
  .ch-card.featured{transform:none}
  .pager{grid-template-columns:1fr}
  #chart{height:280px}
  .site-footer{margin-top:64px;padding:48px 0 32px}
  .footer-grid{grid-template-columns:1fr;gap:34px}
}

/* ---------- dark formula band ---------- */
.method-band{background:var(--ink);color:var(--paper);padding:82px 0;margin-top:68px}
.method-grid{display:grid;grid-template-columns:.86fr 1.14fr;align-items:center;gap:90px}
.method-band .eyebrow{color:var(--mint)}
.method-band .eyebrow-dot{background:var(--mint)}
.method-band h2{margin-top:0;color:var(--paper)}
.method-band h2 em{color:var(--mint)}
.method-intro p{max-width:36ch;margin-bottom:0;color:#a8bdb6;font-size:15.5px}
.formula-card{padding:38px 38px 30px;border:1px solid rgba(255,253,248,.26)}
.formula-tag{font:10px var(--mono);letter-spacing:.09em;text-transform:uppercase;color:var(--mint)}
.formula{
  margin:44px 0 14px;color:var(--white);font-family:var(--display);font-weight:500;
  font-size:clamp(30px,4vw,50px);line-height:1.15;letter-spacing:.01em;
}
.formula-legend{margin:0 0 40px;font:11px var(--mono);color:#a8bdb6;letter-spacing:.02em}
.parameter-row{
  display:grid;grid-template-columns:repeat(3,1fr);gap:16px;padding-top:20px;
  border-top:1px solid rgba(255,253,248,.2);color:#a8bdb6;font:10px var(--mono);line-height:1.6;
}
.parameter-row b{display:block;margin-bottom:5px;color:var(--paper);font-size:15px;font-weight:400;font-family:var(--body)}

/* ---------- takeaway cards ---------- */
.takeaways{padding:68px 0 0}
@media (max-width:900px){
  .method-band{padding:70px 0;margin-top:64px}
  .method-grid{grid-template-columns:1fr;gap:40px}
  .formula-card{padding:26px 20px 22px}
  .formula{margin:32px 0 12px}
  .parameter-row{grid-template-columns:1fr;gap:18px}
  .takeaways{padding:64px 0 0}
}

/* ---------- chapter 05: small multiples + correlation ---------- */
.eq-panels{
  display:grid;grid-template-columns:repeat(5,1fr);gap:1px;
  background:var(--line);border:1px solid var(--line);margin:26px 0 10px;
}
.eq-panel{background:var(--white);padding:16px 16px 12px}
.eq-head{display:flex;justify-content:space-between;align-items:baseline;gap:8px;margin-bottom:10px}
.eq-t{font:500 11px var(--mono);letter-spacing:.06em;color:var(--ink-soft)}
.eq-v{font-family:var(--display);font-weight:650;font-size:21px;letter-spacing:-.01em;color:var(--ink)}
.eq-spark{display:block;width:100%;height:84px;overflow:visible}
.eq-line{fill:none;stroke-width:2;vector-effect:non-scaling-stroke}
.eq-area{fill:rgba(196,69,44,.10);stroke:none}
.eq-base{stroke:var(--line);stroke-width:1;stroke-dasharray:2 3;vector-effect:non-scaling-stroke}
.eq-dot{stroke:var(--white);stroke-width:1.5;vector-effect:non-scaling-stroke}
.eq-scale{font:10px var(--mono);letter-spacing:.04em;color:var(--ink-soft);margin:0 0 26px;max-width:none}

table.corr{width:auto;min-width:min(100%,440px)}
table.corr th,table.corr td{text-align:center;padding:9px 12px;border:1px solid var(--white)}
table.corr td.rh{text-align:left;color:var(--ink-soft);background:transparent}
table.corr td.diag{background:transparent;color:var(--ink-soft)}
table.corr caption{caption-side:bottom;padding-top:12px}

@media (max-width:900px){
  .eq-panels{grid-template-columns:repeat(2,1fr)}
  /* five panels in a two-wide grid leaves a hole; let the last one span */
  .eq-panels>.eq-panel:last-child{grid-column:1 / -1}
  .eq-spark{height:76px}
}

/* ---------- built-with strip ---------- */
.builtwith{
  display:flex;flex-wrap:wrap;align-items:baseline;gap:10px 26px;
  padding:24px max(40px,calc((100% - 1120px)/2));
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);margin-top:68px;
}
.builtwith .lab{font:10px var(--mono);letter-spacing:.09em;text-transform:uppercase;color:var(--ink-soft);margin-right:6px}
.builtwith ul{display:flex;flex-wrap:wrap;gap:10px 22px;list-style:none;margin:0;padding:0}
.builtwith li{font:12px var(--mono);color:var(--ink)}
.builtwith li span{color:var(--ink-soft)}
@media (max-width:900px){.builtwith{padding:20px 19px;margin-top:52px;gap:8px 18px}}