/* An old-web page: serif text on white, navy headings and rules, warm ochre tags.
   System fonts only (no web-font download); pictures and figures bring the rest. */
:root{
  --paper:#ffffff;
  --paper-2:#f1f4f7;
  --ink:#243447;
  --muted:#526276;
  --navy:#193653;
  --link:#234f78;
  --visited:#526782;
  --rule:#193653;
  --line:#b8c5d2;
  --tag-ink:#745020;
  --tag-paper:#f6efdf;
  --tag-line:#b69a70;
  --serif:"Times New Roman",Times,"Liberation Serif",serif;
  --mono:"Courier New",Courier,"Liberation Mono",monospace;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--serif);
  font-size:20px;line-height:1.55;overflow-wrap:anywhere;-webkit-font-smoothing:antialiased}
a{color:var(--link);text-decoration:underline;text-underline-offset:2px}
a:visited{color:var(--visited)}
a:hover{background:var(--navy);color:var(--paper);text-decoration:none}
a:focus-visible{outline:2px solid var(--navy);outline-offset:2px}
.skip-link{position:absolute;top:8px;left:16px;z-index:1;padding:8px 12px;
  background:var(--paper);transform:translateY(-150%)}
.skip-link:focus{transform:translateY(0)}
[id]{scroll-margin-top:20px}
strong{font-weight:bold}
h1,h2,h3,h4,h5,h6{color:var(--navy)}

/* ---- shared ---- */
.eyebrow{font:15px var(--mono);letter-spacing:.02em;color:var(--muted);margin-bottom:4px;display:block}
.tags{margin:0 0 6px}
.tag{display:inline-block;font:12px/1.4 var(--mono);text-transform:uppercase;letter-spacing:.03em;
  color:var(--tag-ink);border:1px solid var(--tag-line);padding:0 5px;margin:0 4px 4px 0;background:var(--tag-paper)}
.tag.tag--wip{background:var(--tag-ink);border-color:var(--tag-ink);color:var(--paper)}
.note{border:1px solid var(--rule);border-left:4px solid var(--rule);background:var(--paper-2);
  padding:10px 14px;margin:20px 0;font-size:17px}
article>.note{margin:20px 24px}  /* line up with the post text */

/* ====================== INDEX / LANDING ====================== */
.hero{padding:0 24px 10px}
.hero-inner{max-width:992px;margin:0 auto;border-bottom:2px solid var(--rule);padding-bottom:22px}
.hero h1{font:bold clamp(38px,6vw,60px)/1.05 var(--serif);margin:4px 0 14px;letter-spacing:-.01em}
.lede{font-size:23px;line-height:1.45;max-width:46em;margin:0}
.lede.bio{margin-top:10px;font-size:20px;color:var(--muted)}
.book-cta{margin-top:18px}
.book-link{display:inline-flex;align-items:center;gap:8px;padding:6px 0;
  font:19px/1.55 var(--serif);color:var(--link);text-decoration:underline;text-underline-offset:2px}
.book-link:visited{color:var(--visited)}
.book-link:hover{background:var(--navy);color:var(--paper);text-decoration:none}
.book-icon{width:20px;height:20px;flex:none;fill:none;stroke:currentColor;
  stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round}
.topic-nav{display:flex;flex-wrap:wrap;gap:4px 20px;margin-top:20px;font-size:17px}
.topic-nav a{padding:6px 0}
.grid-wrap{max-width:1040px;margin:0 auto;padding:6px 24px 50px}
.section{margin-top:34px}
.section:first-child{margin-top:16px}
.section-title{font:bold 30px/1.15 var(--serif);margin:0;padding-bottom:3px;border-bottom:1px solid var(--rule)}
.section-title{display:flex;align-items:center;gap:12px}
.section-icon{display:block;flex:0 0 96px;width:96px;height:64px}
.section-icon img{display:block;width:96px;height:64px;image-rendering:pixelated}
.section-animation-toggle{margin-top:8px;padding:4px 0;border:0;background:transparent;
  font:12px/1.5 var(--mono);color:var(--muted);text-decoration:underline;text-underline-offset:3px;cursor:pointer}
.section-animation-toggle:hover{color:var(--navy)}
.section-animation-toggle:focus-visible{outline:2px solid var(--navy);outline-offset:3px}
.section-desc{font-size:19px;color:var(--muted);margin:6px 0 14px}
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,300px),1fr));gap:0;
  border-top:1px solid var(--rule);border-left:1px solid var(--rule)}
.card{display:block;padding:16px 18px 18px;color:var(--ink);text-decoration:none;
  border-right:1px solid var(--rule);border-bottom:1px solid var(--rule);background:var(--paper)}
.card:visited{color:var(--ink)}
.card h3{font:bold 24px/1.15 var(--serif);margin:6px 0 8px;color:var(--link);text-decoration:underline;
  text-underline-offset:2px}
.card:visited h3{color:var(--visited)}
.card time{font-size:14px;color:var(--muted);white-space:nowrap}
.card p{margin:0;font-size:18px;color:var(--muted)}
.card:hover{background:var(--paper-2);color:var(--ink)}
.card:focus-visible{position:relative;z-index:1;outline-offset:-4px;background:var(--paper-2)}

/* ====================== POST PAGE ====================== */
article,.post-foot,.back{max-width:820px;margin-left:auto;margin-right:auto}
.back{display:inline-block;margin-left:max(24px,calc(50% - 410px));margin-top:22px;font-size:18px}
.post-head{border-bottom:2px solid var(--rule);margin:0 24px;padding:10px 0 14px}
.post-head h1{font:bold clamp(32px,5vw,48px)/1.08 var(--serif);margin:8px 0 10px}
.post-title-row{display:flex;align-items:baseline;gap:0 20px;flex-wrap:wrap}
.post-title-row time{font-size:16px;color:var(--muted);white-space:nowrap;margin-bottom:10px}
.post-head .subtitle{font-size:22px;color:var(--muted);margin:0 0 10px}
.source-link{margin:6px 0 0}
.post-foot{padding:16px 24px 60px;margin-top:40px;border-top:2px solid var(--rule);color:var(--muted);font-size:16px}

/* notebook flow */
.nb{padding:0 24px}
.md{margin:18px 0}
.md h2,.md h3,.md h4,.md h5,.md h6{font-family:var(--serif);font-weight:bold;line-height:1.15}
.md h2{font-size:32px;margin:38px 0 10px;padding-bottom:3px;border-bottom:1px solid var(--rule)}
.md h3{font-size:26px;margin:30px 0 8px}
.md h4{font-size:22px;margin:24px 0 6px;font-style:italic}
.md p{margin:12px 0}
.md img{max-width:100%;height:auto;display:block;margin:20px auto;border:1px solid var(--rule)}
.md ul,.md ol{padding-left:26px}
.md li{margin:5px 0}
.md blockquote{border-left:4px solid var(--rule);margin:18px 0;padding:4px 18px;color:var(--muted);background:var(--paper-2)}
.md table{border-collapse:collapse;width:100%;margin:20px 0;font-size:17px;display:block;overflow-x:auto}
.md th,.md td{border:1px solid var(--rule);padding:6px 10px;text-align:left}
.md th{background:var(--paper-2);font-weight:bold}
/* inline code only, never the multi-line code inside <pre> */
.md :not(pre)>code{font-family:var(--mono);font-size:.85em;background:var(--paper-2);padding:0 3px;border:1px solid var(--line)}
.md pre.highlight code{background:none;border:none;padding:0;color:inherit;font-size:15px}

/* display equations + figures (markdown posts) */
.md .eq{border:1px solid var(--line);border-left:4px solid var(--rule);padding:4px 16px;margin:16px 0;overflow-x:auto}
.math{max-width:100%;overflow-x:auto;overflow-wrap:normal}
mjx-container[display="true"]{max-width:100%;overflow-x:auto;overflow-y:hidden}
.md .figure{margin:22px 0}
.md .figure svg{width:100%;height:auto;border:1px solid var(--rule);padding:12px;background:var(--paper)}
.md .cap{font-size:17px;font-style:italic;color:var(--muted);margin:8px 4px 0;text-align:center}

/* code cells */
.code-cell{margin:16px 0}
pre.highlight{background:var(--paper-2);border:1px solid var(--rule);padding:14px 16px;overflow-x:auto;
  font-family:var(--mono);font-size:15px;line-height:1.5;margin:0;overflow-wrap:normal}
pre.highlight code{font-family:var(--mono);background:none;border:none;padding:0;color:inherit}
.out{margin:0 0 4px;border:1px solid var(--rule);border-top:none;padding:10px 14px;overflow-x:auto;background:var(--paper)}
.out pre{margin:0;font-family:var(--mono);font-size:14px;white-space:pre-wrap}
.out img{max-width:100%;height:auto}

.site-foot{max-width:1040px;margin:0 auto;padding:14px 24px 50px;border-top:2px solid var(--rule);
  color:var(--muted);font-size:16px}

@media(max-width:640px){
  body{font-size:18px}
  .hero{padding:22px 16px 6px} .grid-wrap{padding:4px 16px 40px} .nb{padding:0 16px}
  .post-head{margin:0 16px} .back{margin-left:16px} article>.note{margin:16px}
  .lede{font-size:20px} .lede.bio{font-size:18px}
  .grid{grid-template-columns:1fr}
}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}