:root{
  --paper:#f7f4ec;
  --paper-2:#fffdf7;
  --ink:#211f1a;
  --ink-soft:#4b4740;
  --rule:#d8d1be;
  --accent:#1f5d54;
  --accent-soft:#e3ece8;
  --gold:#9a6b2e;
  --shadow:0 1px 2px rgba(33,31,26,.06),0 8px 24px rgba(33,31,26,.06);
}
*{box-sizing:border-box;}
html,body{margin:0;padding:0;}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:'Newsreader',Georgia,serif;
  font-size:18px;
  line-height:1.62;
  -webkit-font-smoothing:antialiased;
}
.wrap{max-width:820px;margin:0 auto;padding:64px 28px 120px;}

/* ---- masthead ---- */
.masthead{border-bottom:2px solid var(--ink);padding-bottom:26px;margin-bottom:8px;}
.kicker{
  font-family:'IBM Plex Mono',monospace;font-size:11.5px;letter-spacing:.22em;
  text-transform:uppercase;color:var(--accent);margin-bottom:18px;
}
h1.title{
  font-family:'Fraunces',serif;font-weight:600;font-size:46px;line-height:1.08;
  margin:0 0 14px;letter-spacing:-.01em;
}
h1.title em{font-style:italic;color:var(--accent);}
.standfirst{
  font-size:20px;line-height:1.5;color:var(--ink-soft);font-style:italic;
  max-width:62ch;margin:0 0 22px;
}
.meta-grid{
  display:grid;grid-template-columns:repeat(2,1fr);gap:4px 36px;
  font-family:'IBM Plex Mono',monospace;font-size:12px;color:var(--ink-soft);
  border-top:1px solid var(--rule);padding-top:18px;
}
.meta-grid div span{color:var(--ink);}

.nav-back{
  display:inline-block;font-family:'IBM Plex Mono',monospace;font-size:11px;
  letter-spacing:.16em;text-transform:uppercase;color:var(--accent);
  text-decoration:none;margin-bottom:18px;
}
.nav-back:hover{text-decoration:underline;}

/* ---- table of contents ---- */
.toc{
  background:var(--paper-2);border:1px solid var(--rule);border-radius:4px;
  padding:24px 28px;margin:40px 0 8px;box-shadow:var(--shadow);
}
.toc h2{
  font-family:'IBM Plex Mono',monospace;font-size:12px;letter-spacing:.18em;
  text-transform:uppercase;margin:0 0 14px;color:var(--accent);font-weight:500;
}
.toc ol{margin:0;padding:0;list-style:none;counter-reset:toc;}
.toc li{
  counter-increment:toc;padding:7px 0;border-bottom:1px dotted var(--rule);
  font-size:16px;
}
.toc li:last-child{border-bottom:none;}
.toc li::before{
  content:counter(toc,decimal-leading-zero);
  font-family:'IBM Plex Mono',monospace;font-size:11px;color:var(--gold);
  margin-right:14px;
}
.toc a{color:var(--ink);text-decoration:none;}
.toc a:hover{color:var(--accent);text-decoration:underline;}
.toc .sum{
  display:block;font-size:14px;color:var(--ink-soft);font-style:italic;
  margin-top:2px;margin-left:28px;
}

/* ---- sections ---- */
section{margin-top:58px;scroll-margin-top:24px;}
.part-label{
  font-family:'IBM Plex Mono',monospace;font-size:11.5px;letter-spacing:.2em;
  text-transform:uppercase;color:var(--gold);margin-bottom:8px;
}
h2.part{
  font-family:'Fraunces',serif;font-weight:600;font-size:31px;line-height:1.14;
  margin:0 0 6px;letter-spacing:-.01em;
}
h2.part::after{
  content:"";display:block;width:54px;height:3px;background:var(--accent);
  margin-top:14px;
}
h3{
  font-family:'Fraunces',serif;font-weight:600;font-size:21px;
  margin:34px 0 6px;letter-spacing:-.005em;
}
h4{
  font-family:'IBM Plex Mono',monospace;font-size:13px;letter-spacing:.04em;
  text-transform:uppercase;color:var(--accent);margin:26px 0 4px;font-weight:500;
}
p{margin:12px 0;}
strong{font-weight:600;}
em{font-style:italic;}
.lead{font-size:19px;color:var(--ink-soft);}

.formula{
  background:var(--paper-2);border-left:3px solid var(--accent);
  font-family:'IBM Plex Mono',monospace;font-size:14px;line-height:1.7;
  padding:14px 18px;margin:18px 0;border-radius:0 4px 4px 0;overflow-x:auto;
}
/* KaTeX-rendered display equations sit flush inside the .formula card */
.formula .katex-display{margin:0;}
.formula .katex{font-size:1.15em;}
.katex{font-size:1.05em;}
.callout{
  background:var(--accent-soft);border-radius:4px;padding:16px 20px;margin:20px 0;
  font-size:16px;
}
.callout .tag{
  font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.15em;
  text-transform:uppercase;color:var(--accent);display:block;margin-bottom:4px;
}
ul.plain{margin:12px 0;padding-left:22px;}
ul.plain li{margin:7px 0;}
a.ref-link{
  color:var(--accent);text-decoration:none;
  border-bottom:1px solid var(--accent-soft);
  white-space:nowrap;font-style:normal;
}
a.ref-link:hover{border-bottom-color:var(--accent);}
/* inline source links (DOIs, arXiv, repositories) may wrap */
ul.plain li a.ref-link[href*="doi.org"],
ul.plain li a.ref-link[href*="github.com"]{white-space:normal;word-break:break-word;}

/* component cards */
.component{
  border:1px solid var(--rule);border-radius:4px;background:var(--paper-2);
  padding:22px 26px;margin:22px 0;box-shadow:var(--shadow);
}
.component .cnum{
  font-family:'IBM Plex Mono',monospace;font-size:12px;color:var(--gold);
  letter-spacing:.1em;
}
.component h3{margin-top:4px;}

/* paper table */
table{border-collapse:collapse;width:100%;margin:20px 0;font-size:15px;}
th,td{border:1px solid var(--rule);padding:9px 12px;text-align:left;vertical-align:top;}
th{
  background:var(--accent);color:var(--paper-2);font-family:'IBM Plex Mono',monospace;
  font-size:11px;letter-spacing:.08em;text-transform:uppercase;font-weight:500;
}
tr:nth-child(even) td{background:var(--paper);}

/* ---- chapter cards on index ---- */
.chapter-grid{display:grid;grid-template-columns:1fr;gap:14px;margin-top:24px;}
.chapter-card{
  display:block;text-decoration:none;color:var(--ink);
  border:1px solid var(--rule);border-radius:4px;background:var(--paper-2);
  padding:20px 24px;box-shadow:var(--shadow);transition:border-color .15s;
}
.chapter-card:hover{border-color:var(--accent);}
.chapter-card .pid{
  font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.16em;
  text-transform:uppercase;color:var(--gold);
}
.chapter-card .ctitle{
  font-family:'Fraunces',serif;font-weight:600;font-size:21px;
  margin:4px 0 6px;letter-spacing:-.005em;
}
.chapter-card .csum{font-size:16px;color:var(--ink-soft);margin:0;}
.chapter-card .arrow{
  font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.16em;
  color:var(--accent);text-transform:uppercase;display:inline-block;margin-top:10px;
}

/* ---- prev / next nav ---- */
.pager{
  display:grid;grid-template-columns:1fr 1fr;gap:14px;margin-top:60px;
  border-top:1px solid var(--rule);padding-top:22px;
}
.pager a{
  display:block;text-decoration:none;color:var(--ink);
  border:1px solid var(--rule);border-radius:4px;background:var(--paper-2);
  padding:14px 18px;box-shadow:var(--shadow);
}
.pager a:hover{border-color:var(--accent);}
.pager .dir{
  font-family:'IBM Plex Mono',monospace;font-size:10.5px;letter-spacing:.16em;
  text-transform:uppercase;color:var(--accent);display:block;margin-bottom:4px;
}
.pager .ctitle{font-family:'Fraunces',serif;font-weight:600;font-size:17px;}
.pager .next{text-align:right;}

/* ---- checklist ---- */
.checklist-intro{margin-top:58px;}
.progress-shell{
  position:sticky;top:0;background:var(--paper);padding:14px 0 10px;
  z-index:5;border-bottom:1px solid var(--rule);margin-bottom:8px;
}
.progress-row{display:flex;align-items:baseline;justify-content:space-between;margin-bottom:6px;}
.progress-row .lbl{
  font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.16em;
  text-transform:uppercase;color:var(--accent);
}
.progress-row .count{font-family:'IBM Plex Mono',monospace;font-size:13px;color:var(--ink);}
.bar{height:7px;background:var(--rule);border-radius:4px;overflow:hidden;}
.bar > i{
  display:block;height:100%;width:0;background:var(--accent);
  transition:width .35s ease;
}

.phase{margin-top:34px;}
.phase-head{
  display:flex;align-items:baseline;gap:12px;border-bottom:2px solid var(--ink);
  padding-bottom:6px;margin-bottom:4px;
}
.phase-head .pid{
  font-family:'IBM Plex Mono',monospace;font-size:12px;color:var(--paper-2);
  background:var(--ink);padding:3px 8px;border-radius:3px;letter-spacing:.05em;
}
.phase-head h3{margin:0;font-size:20px;}
.phase-note{font-size:15px;color:var(--ink-soft);font-style:italic;margin:8px 0 6px;}

.task{
  display:flex;gap:13px;align-items:flex-start;padding:11px 4px;
  border-bottom:1px dotted var(--rule);
}
.task:last-child{border-bottom:none;}
.task input[type=checkbox]{
  appearance:none;-webkit-appearance:none;
  width:20px;height:20px;min-width:20px;margin-top:3px;
  border:1.6px solid var(--accent);border-radius:4px;background:var(--paper-2);
  cursor:pointer;position:relative;transition:background .15s;
}
.task input[type=checkbox]:checked{background:var(--accent);}
.task input[type=checkbox]:checked::after{
  content:"";position:absolute;left:6px;top:2px;width:5px;height:10px;
  border:solid var(--paper-2);border-width:0 2.4px 2.4px 0;transform:rotate(45deg);
}
.task label{cursor:pointer;font-size:16.5px;line-height:1.5;flex:1;}
.task .tcode{
  font-family:'IBM Plex Mono',monospace;font-size:11px;color:var(--gold);
  margin-right:7px;
}
.task.done label{color:var(--ink-soft);}
.task.done label .ttitle{text-decoration:line-through;}
.task .deliver{
  display:block;font-size:13.5px;color:var(--ink-soft);font-style:italic;
  margin-top:2px;
}
.gate{
  background:var(--accent-soft);border-radius:4px;padding:12px 16px;margin:14px 0;
  font-size:15px;
}
.gate b{font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.12em;
  text-transform:uppercase;color:var(--accent);}

.controls{margin:18px 0 4px;display:flex;gap:10px;flex-wrap:wrap;}
.controls button{
  font-family:'IBM Plex Mono',monospace;font-size:11px;letter-spacing:.08em;
  text-transform:uppercase;background:var(--paper-2);color:var(--ink);
  border:1px solid var(--rule);border-radius:3px;padding:7px 12px;cursor:pointer;
}
.controls button:hover{border-color:var(--accent);color:var(--accent);}

footer{
  margin-top:80px;padding-top:22px;border-top:2px solid var(--ink);
  font-family:'IBM Plex Mono',monospace;font-size:11.5px;color:var(--ink-soft);
  line-height:1.7;
}

@media (max-width:560px){
  body{font-size:16.5px;}
  .wrap{padding:40px 18px 90px;}
  h1.title{font-size:33px;}
  h2.part{font-size:25px;}
  .meta-grid{grid-template-columns:1fr;}
  .pager{grid-template-columns:1fr;}
  .pager .next{text-align:left;}
}
@media print{
  .progress-shell,.controls{display:none;}
  body{background:#fff;}
  .component,.toc,.chapter-card,.pager a{box-shadow:none;}
}