:root{
  --paper:#f7f8fa;
  --paper-2:#eef1f5;
  --ink:#101c33;
  --ink-soft:#26354f;
  --muted:#4a5a75;
  --rule:#c9d1dd;
  --rule-strong:#8f9db3;
  --accent:#a3371c;
  --accent-deep:#7d2814;
  --focus:#0b4ea2;
  --max:1180px;
  --serif:Georgia,"Iowan Old Style","Palatino Linotype","Times New Roman",serif;
  --sans:"Helvetica Neue",Helvetica,Arial,"Segoe UI",Roboto,sans-serif;
}

*,*::before,*::after{box-sizing:border-box}

html{-webkit-text-size-adjust:100%}

body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--serif);
  font-size:1.0625rem;
  line-height:1.62;
  overflow-wrap:break-word;
}

a{color:var(--accent-deep);text-underline-offset:.18em}
a:hover{color:var(--accent)}

a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible,[tabindex]:focus-visible{
  outline:3px solid var(--focus);
  outline-offset:2px;
  border-radius:2px;
}

.skip-link{
  position:absolute;left:-9999px;top:0;z-index:50;
  background:var(--ink);color:#fff;padding:.6rem 1rem;font-family:var(--sans);
}
.skip-link:focus{left:.75rem;top:.75rem}

/* ---------- shared header ---------- */
.site-header{border-bottom:1px solid var(--rule-strong);background:var(--paper)}
.header-inner{
  max-width:var(--max);margin:0 auto;padding:1.15rem 1.5rem;
  display:flex;flex-wrap:wrap;gap:.75rem 1.5rem;align-items:baseline;justify-content:space-between;
}
.brand{margin:0;font-family:var(--sans);font-size:1.0625rem;font-weight:700;letter-spacing:.02em;line-height:1.25}
.brand a{color:var(--ink);text-decoration:none;border-bottom:2px solid var(--accent);padding-bottom:.1rem}
.brand a:hover{color:var(--accent-deep)}
.brand-sub{display:block;font-weight:400;font-size:.72rem;letter-spacing:.16em;text-transform:uppercase;color:var(--muted);margin-top:.28rem}
.site-nav ul{list-style:none;display:flex;flex-wrap:wrap;gap:.35rem 1.35rem;margin:0;padding:0}
.site-nav a{
  font-family:var(--sans);font-size:.82rem;letter-spacing:.09em;text-transform:uppercase;
  color:var(--ink-soft);text-decoration:none;border-bottom:1px solid transparent;padding-bottom:.15rem;
}
.site-nav a:hover,.site-nav a:focus-visible{border-bottom-color:var(--accent);color:var(--accent-deep)}

/* ---------- shared footer ---------- */
.site-footer{border-top:1px solid var(--rule-strong);background:var(--paper-2);margin-top:0}
.footer-inner{
  max-width:var(--max);margin:0 auto;padding:2rem 1.5rem 2.25rem;
  display:flex;flex-wrap:wrap;gap:1rem 2.5rem;align-items:flex-start;justify-content:space-between;
  font-family:var(--sans);
}
.footer-brand{margin:0;font-weight:700;font-size:.95rem;color:var(--ink);flex:0 0 auto}
.footer-note{margin:0;max-width:34ch;font-size:.82rem;line-height:1.55;color:var(--muted);flex:1 1 18rem}
.footer-nav ul{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:.35rem 1.1rem;max-width:44rem}
.footer-nav a{font-size:.8rem;color:var(--ink-soft);text-decoration:none;border-bottom:1px solid var(--rule-strong);padding-bottom:.1rem}
.footer-nav a:hover,.footer-nav a:focus-visible{color:var(--accent-deep);border-bottom-color:var(--accent)}

/* ---------- page shells ---------- */
.page-shell,.page{max-width:var(--max);margin:0 auto;padding:0 1.5rem}
.page-shell{padding-bottom:4rem}

.article{padding-bottom:4rem}
.article-header{border-bottom:2px solid var(--ink);padding:2.5rem 0 1.5rem;margin-bottom:1.75rem}
.article-header h1{font-size:clamp(1.85rem,4.6vw,3.1rem);line-height:1.1;margin:.35rem 0 .85rem;letter-spacing:-.01em;max-width:24ch}
.article-body{max-width:68ch}
.article-body h2{font-size:clamp(1.3rem,2.6vw,1.7rem);line-height:1.2;margin:2.4rem 0 .7rem;padding-top:.4rem;border-top:1px solid var(--rule)}
.article-body h3{font-size:1.12rem;margin:1.7rem 0 .5rem}
.article-body p{margin:0 0 1rem}
.article-body ul,.article-body ol{margin:0 0 1.15rem;padding-left:1.3rem}
.article-body li{margin-bottom:.45rem}

.eyebrow{
  font-family:var(--sans);font-size:.72rem;letter-spacing:.19em;text-transform:uppercase;
  color:var(--accent-deep);margin:0 0 .4rem;font-weight:700;
}
.lede{font-size:clamp(1.06rem,1.9vw,1.24rem);line-height:1.55;color:var(--ink-soft);margin:0 0 1rem}
.fine{font-family:var(--sans);font-size:.8rem;line-height:1.55;color:var(--muted)}
.scope-note{font-family:var(--sans);font-size:.86rem;line-height:1.6;color:var(--ink-soft);border-left:3px solid var(--accent);padding:.15rem 0 .15rem .9rem;margin:1.1rem 0 0}

/* ---------- homepage opening ---------- */
.opening{padding:3rem 0 1.5rem;border-bottom:1px solid var(--rule-strong)}
.opening h1{
  font-size:clamp(2rem,5.4vw,3.9rem);line-height:1.04;letter-spacing:-.015em;
  margin:.4rem 0 1.6rem;max-width:19ch;
}
.opening-grid{display:grid;grid-template-columns:minmax(0,1.05fr) minmax(0,.95fr);gap:2.5rem 3rem;align-items:start}
.opening-copy p{margin:0 0 1rem}
.opening-actions{margin:1.4rem 0 0;display:flex;flex-wrap:wrap;gap:.75rem 1rem;align-items:center;font-family:var(--sans)}
.action-primary{
  display:inline-block;background:var(--ink);color:#fff;text-decoration:none;
  font-family:var(--sans);font-size:.86rem;letter-spacing:.05em;text-transform:uppercase;font-weight:700;
  padding:.7rem 1.15rem;border:1px solid var(--ink);
}
.action-primary:hover,.action-primary:focus-visible{background:var(--accent-deep);border-color:var(--accent-deep);color:#fff}
.action-secondary{
  display:inline-block;font-family:var(--sans);font-size:.86rem;letter-spacing:.04em;
  color:var(--ink);text-decoration:none;border-bottom:2px solid var(--accent);padding-bottom:.12rem;
}
.action-secondary:hover,.action-secondary:focus-visible{color:var(--accent-deep)}

.section-figure{margin:0;border:1px solid var(--rule-strong);background:#fff;padding:.85rem .9rem 1rem}
.room-svg{display:block;width:100%;height:auto}
.rm-paper{fill:#fff}
.rm-frame{stroke:var(--ink);stroke-width:2.4;fill:none}
.rm-water{stroke:var(--accent);stroke-width:2;stroke-dasharray:8 6;fill:none}
.rm-hair{stroke:var(--rule-strong);stroke-width:1.4;stroke-dasharray:3 4}
.rm-dot{fill:#fff;stroke:var(--ink);stroke-width:2.2}
.rm-num{font-family:var(--sans);font-size:14px;font-weight:700;fill:var(--ink);text-anchor:middle}
.rm-cap{font-family:var(--sans);font-size:12px;fill:var(--ink-soft);letter-spacing:.02em}
.rm-dim{font-family:var(--sans);font-size:11px;fill:var(--muted)}
.rm-legend{stroke:var(--accent);stroke-width:2;stroke-dasharray:8 6}
.section-figure figcaption{font-family:var(--sans);font-size:.76rem;line-height:1.5;color:var(--muted);margin-top:.6rem}
.marker-log{list-style:none;margin:.85rem 0 0;padding:.85rem 0 0;border-top:1px solid var(--rule);font-family:var(--sans);font-size:.82rem;line-height:1.5;color:var(--ink-soft)}
.marker-log li{display:grid;grid-template-columns:1.6rem 1fr;gap:.5rem;margin-bottom:.5rem}
.marker-log li:last-child{margin-bottom:0}
.marker-num{font-weight:700;color:var(--accent-deep);font-variant-numeric:tabular-nums}

/* ---------- chapters ---------- */
.chapter{
  display:grid;grid-template-columns:6.5rem minmax(0,1fr);gap:0 2rem;
  padding:2.6rem 0;border-bottom:1px solid var(--rule-strong);
}
.chapter:last-of-type{border-bottom:0}
.chapter-num{
  margin:0;font-family:var(--serif);font-size:clamp(3.2rem,7vw,5rem);line-height:.85;
  color:var(--rule-strong);font-variant-numeric:tabular-nums;letter-spacing:-.03em;
  position:sticky;top:1rem;align-self:start;
}
.chapter-body{min-width:0}
.chapter-body h2{font-size:clamp(1.4rem,3vw,2.05rem);line-height:1.16;margin:.2rem 0 1.2rem;max-width:30ch;letter-spacing:-.005em}
.chapter-body h3{font-size:1.1rem;margin:0 0 .5rem}
.chapter-body p{margin:0 0 1rem}
.wide-body{max-width:none}
.section-intro{max-width:64ch}
.split{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(0,.85fr);gap:1.5rem 2.75rem;align-items:start}
.mini-heading{font-family:var(--sans);font-size:.72rem;letter-spacing:.17em;text-transform:uppercase;color:var(--accent-deep)}

.plain-list{margin:0 0 1rem;padding-left:1.15rem}
.plain-list li{margin-bottom:.5rem}
.plain-list.tight li{margin-bottom:.35rem}

.checklist-block{border:1px solid var(--rule-strong);background:#fff;padding:1.1rem 1.2rem}
.checklist-block .plain-list{font-size:.95rem}

/* guide ledger */
.guide-ledger{list-style:none;margin:0;padding:0;border-top:1px solid var(--rule-strong);counter-reset:none}
.guide-ledger li{
  display:grid;grid-template-columns:3rem minmax(0,1fr);gap:.25rem 1.1rem;
  padding:1.15rem 0 1.3rem;border-bottom:1px solid var(--rule);align-items:start;
}
.guide-index{
  margin:.15rem 0 0;font-family:var(--serif);font-size:1.5rem;color:var(--accent);
  font-variant-numeric:tabular-nums;grid-row:1 / span 2;
}
.guide-ledger h3{margin:0;font-size:1.16rem;line-height:1.3}
.guide-ledger h3 a{color:var(--ink);text-decoration:none;border-bottom:1px solid var(--rule-strong)}
.guide-ledger h3 a:hover,.guide-ledger h3 a:focus-visible{color:var(--accent-deep);border-bottom-color:var(--accent)}
.guide-ledger p{margin:.15rem 0 0;color:var(--ink-soft);font-size:.96rem;grid-column:2}

/* source table */
.table-wrap{overflow-x:auto;border:1px solid var(--rule-strong);background:#fff;margin:0 0 1rem;-webkit-overflow-scrolling:touch}
.source-table{border-collapse:collapse;width:100%;min-width:38rem;font-family:var(--sans);font-size:.86rem;line-height:1.5}
.source-table caption{text-align:left;padding:.75rem .9rem;font-size:.74rem;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--rule);caption-side:top}
.source-table th,.source-table td{padding:.8rem .9rem;text-align:left;vertical-align:top;border-bottom:1px solid var(--rule)}
.source-table thead th{background:var(--paper-2);color:var(--ink);font-size:.75rem;letter-spacing:.1em;text-transform:uppercase;border-bottom:1px solid var(--rule-strong)}
.source-table tbody th{font-weight:600;color:var(--ink);width:56%}
.source-table tbody td{color:var(--ink-soft)}
.source-table tbody tr:last-child th,.source-table tbody tr:last-child td{border-bottom:0}

.closing-links{border-left:1px solid var(--rule-strong);padding-left:1.5rem}
.closing-links p:first-child{margin-top:0}

/* ---------- tool page ---------- */
.tool-hero{border-bottom:2px solid var(--ink);padding:2.5rem 0 1.5rem;margin-bottom:1.6rem}
.tool-hero h1{font-size:clamp(1.85rem,4.6vw,3rem);line-height:1.08;margin:.35rem 0 .9rem;max-width:24ch}
.tool-hero .lede{max-width:62ch}
.tool-hero .scope-note{max-width:66ch}

.tool-panel{margin:0 0 2.5rem}
.tool-panel h2{font-size:clamp(1.3rem,2.6vw,1.7rem);margin:0 0 1rem}
.fieldset-frame{border:1px solid var(--rule-strong);background:#fff;padding:1.25rem 1.3rem}
fieldset{border:0;margin:0;padding:0;min-width:0}
fieldset.group{border-top:1px solid var(--rule);padding:1.1rem 0 .4rem;margin:0 0 .4rem}
fieldset.group:first-of-type{border-top:0;padding-top:0}
legend{font-family:var(--sans);font-weight:700;font-size:.95rem;color:var(--ink);padding:0 .2rem}
fieldset.group>legend{font-size:1rem;color:var(--accent-deep)}
.hint{font-family:var(--sans);font-size:.8rem;line-height:1.55;color:var(--muted);margin:.2rem 0 .85rem;max-width:64ch}
.field-row{margin:0 0 1rem}
.field-row label{display:block;font-family:var(--sans);font-weight:600;font-size:.9rem;color:var(--ink);margin-bottom:.3rem}
input[type="text"],select,textarea{
  display:block;width:100%;max-width:34rem;min-height:2.6rem;
  font-family:var(--sans);font-size:1rem;line-height:1.45;color:var(--ink);
  background:#fff;border:1px solid var(--rule-strong);padding:.5rem .6rem;border-radius:0;
}
textarea{min-height:6.5rem;resize:vertical}
input[type="text"]::placeholder{color:#5f6d85;opacity:1}
input[type="text"]:disabled,select:disabled,textarea:disabled{background:var(--paper-2);color:var(--ink-soft)}
.check-row{display:flex;align-items:flex-start;gap:.6rem;margin:0 0 .65rem;max-width:60ch}
.check-row input[type="checkbox"]{width:1.15rem;height:1.15rem;margin:.18rem 0 0;flex:0 0 auto;accent-color:var(--ink)}
.check-row label{font-family:var(--sans);font-size:.9rem;line-height:1.45;color:var(--ink)}
.field-error{font-family:var(--sans);font-size:.82rem;color:#8a1c0a;font-weight:600;margin:.2rem 0 0}
.noscript-note{font-family:var(--sans);background:var(--paper-2);border:1px solid var(--rule-strong);padding:.85rem 1rem;font-size:.88rem;margin:0 0 1.2rem}

.button-row{display:flex;flex-wrap:wrap;gap:.7rem;margin:1.25rem 0 1.5rem}
.button-row button{
  font-family:var(--sans);font-size:.86rem;font-weight:700;letter-spacing:.05em;text-transform:uppercase;
  padding:.72rem 1.15rem;border:1px solid var(--ink);background:#fff;color:var(--ink);cursor:pointer;
}
.button-row button#run{background:var(--ink);color:#fff}
.button-row button#run:hover:not(:disabled){background:var(--accent-deep);border-color:var(--accent-deep)}
.button-row button:hover:not(:disabled){border-color:var(--accent-deep);color:var(--accent-deep)}
.button-row button#run:hover:not(:disabled){color:#fff}
.button-row button:disabled{background:var(--paper-2);color:var(--muted);border-color:var(--rule-strong);cursor:not-allowed}

.results{border:1px solid var(--rule-strong);background:#fff;padding:1.1rem 1.2rem;min-height:5rem}
.results-placeholder{margin:0;color:var(--muted);font-family:var(--sans);font-size:.9rem}
.results pre{
  margin:0;white-space:pre-wrap;overflow-wrap:break-word;font-family:"Courier New",Courier,monospace;
  font-size:.85rem;line-height:1.55;color:var(--ink);max-width:100%;overflow-x:auto;
}

.diagram-section{padding:2rem 0;border-top:1px solid var(--rule-strong);border-bottom:1px solid var(--rule-strong);margin-bottom:2rem}
.diagram-section h2{font-size:clamp(1.25rem,2.4vw,1.55rem);margin:0 0 1.1rem;max-width:40ch;line-height:1.2}
.waterline-figure{margin:0;border:1px solid var(--rule-strong);background:#fff;padding:.85rem .9rem 1rem}
.waterline-svg{display:block;width:100%;height:auto}
.svg-paper{fill:#fff}
.svg-floor{stroke:var(--ink);stroke-width:3}
.svg-wall{stroke:var(--ink);stroke-width:2.4}
.svg-ceiling{stroke:var(--ink);stroke-width:1.6;stroke-dasharray:2 5}
.svg-waterline{stroke:var(--accent);stroke-width:2.4;stroke-dasharray:9 7}
.svg-marker{stroke:var(--rule-strong);stroke-width:1.4;stroke-dasharray:3 4}
.svg-marker-dot{fill:var(--accent)}
.svg-label{font-family:var(--sans);font-size:13px;fill:var(--ink)}
.svg-label-dim{font-family:var(--sans);font-size:12px;fill:var(--muted)}
.waterline-figure figcaption{font-family:var(--sans);font-size:.78rem;line-height:1.5;color:var(--muted);margin-top:.65rem}

.tool-notes{padding-bottom:1rem}
.tool-notes h2{font-size:clamp(1.25rem,2.4vw,1.55rem);margin:0 0 1rem}
.tool-notes .plain-list{font-family:var(--sans);font-size:.9rem;line-height:1.55;color:var(--ink-soft);max-width:70ch}

/* ---------- responsive ---------- */
@media (max-width:1000px){
  .opening-grid,.split{grid-template-columns:minmax(0,1fr)}
  .closing-links{border-left:0;padding-left:0;border-top:1px solid var(--rule);padding-top:1rem}
  .chapter-num{position:static}
}

@media (max-width:760px){
  .header-inner{padding:1rem 1.1rem}
  .page-shell,.page{padding-left:1.1rem;padding-right:1.1rem}
  .chapter{grid-template-columns:minmax(0,1fr);gap:0;padding:2rem 0}
  .chapter-num{font-size:2.6rem;margin-bottom:.4rem;color:var(--rule-strong)}
  .guide-ledger li{grid-template-columns:2.2rem minmax(0,1fr);gap:.2rem .8rem}
  .guide-ledger p{grid-column:2}
  .opening{padding-top:2rem}
  .opening h1{max-width:none}
  .tool-hero,.article-header{padding-top:1.6rem}
  .fieldset-frame{padding:1rem .85rem}
  input[type="text"],select,textarea{max-width:100%}
  .button-row button{flex:1 1 100%}
  .footer-inner{padding:1.5rem 1.1rem 1.75rem}
  .footer-note{max-width:none}
}

@media (max-width:430px){
  body{font-size:1rem}
  .opening-actions{flex-direction:column;align-items:flex-start}
  .action-primary{width:100%;text-align:center}
  .brand-sub{letter-spacing:.12em}
  .source-table{min-width:0;font-size:.82rem}
  .source-table thead{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
  .source-table,.source-table tbody,.source-table tr,.source-table th,.source-table td{display:block;width:100%}
  .source-table tr{border-bottom:1px solid var(--rule-strong);padding:.5rem 0}
  .source-table tr:last-child{border-bottom:0}
  .source-table tbody th{width:auto;padding:.4rem .9rem .15rem;font-weight:700;font-size:.78rem;letter-spacing:.06em;text-transform:uppercase;color:var(--accent-deep);border-bottom:0}
  .source-table tbody td{padding:.1rem .9rem .6rem;border-bottom:0}
  .table-wrap{overflow-x:visible}
  .results pre{font-size:.8rem}
}

@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{animation-duration:.001ms !important;animation-iteration-count:1 !important;transition-duration:.001ms !important;scroll-behavior:auto !important}
}

/* Verified layout corrections */
.chapter-num{color:#5c6c83}