:root {
  --bg: #fbfaf7;
  --surface: #ffffff;
  --ink: #16150f;
  --ink-2: #4a4740;
  --ink-3: #7a766c;
  --line: #e7e3da;
  --accent: #d0312d;
  --accent-ink: #b0221f;
  --accent-soft: #fbe9e7;
  --code-bg: #f3f1ec;
  --serif: 'Iowan Old Style', 'Palatino Linotype', Charter, 'Bitstream Charter', Georgia, serif;
  --sans: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --mono: ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
  --measure: 42rem;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12110e;
    --surface: #1b1a16;
    --ink: #f1eee6;
    --ink-2: #c9c4b8;
    --ink-3: #8f8a7e;
    --line: #2e2c26;
    --accent: #ff5a4f;
    --accent-ink: #ff7a70;
    --accent-soft: #2c1714;
    --code-bg: #23211c;
    color-scheme: dark;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 7.5rem; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 18px/1.65 var(--sans);
  text-rendering: optimizeLegibility;
}
a { color: var(--accent-ink); text-underline-offset: 0.18em; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
img { max-width: 100%; height: auto; }
.wrap { max-width: 72rem; margin: 0 auto; padding-inline: 1.25rem; }
.measure { max-width: var(--measure); margin-inline: auto; }

/* header */
.top {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: saturate(1.4) blur(8px);
  border-bottom: 1px solid var(--line);
}
.top .wrap { display: flex; align-items: center; gap: 1rem; min-height: 3.5rem; }
.brand { display: flex; align-items: center; gap: 0.55rem; color: var(--ink); text-decoration: none; font-weight: 700; letter-spacing: -0.01em; }
.brand-mark { width: 1.6rem; height: 1.6rem; border-radius: 0.4rem; background: var(--accent); color: #fff; display: grid; place-items: center; font: 800 0.8rem/1 var(--sans); }
.nav { margin-left: auto; display: flex; gap: 1.1rem; font-size: 0.92rem; }
.nav a { color: var(--ink-2); text-decoration: none; }
.nav a:hover { color: var(--ink); }
.progress { position: absolute; left: 0; bottom: -1px; height: 2px; background: var(--accent); width: 0; }

/* home */
.hero { padding-block: 3rem 1.5rem; border-bottom: 1px solid var(--line); }
.kicker { font: 600 0.78rem/1.2 var(--sans); letter-spacing: 0.12em; text-transform: uppercase; color: var(--accent-ink); }
.hero h1 { font: 700 clamp(2rem, 5vw, 3.4rem)/1.08 var(--serif); letter-spacing: -0.02em; margin: 0.6rem 0 0.8rem; max-width: 22ch; }
.hero h1 a { color: inherit; text-decoration: none; }
.hero .dek { font-size: 1.15rem; color: var(--ink-2); max-width: 46rem; margin: 0 0 1.2rem; }
.meta { font-size: 0.86rem; color: var(--ink-3); display: flex; flex-wrap: wrap; gap: 0.35rem 1rem; }
.btn { display: inline-flex; align-items: center; gap: 0.4rem; padding: 0.6rem 1rem; border-radius: 999px; background: var(--ink); color: var(--bg); text-decoration: none; font-weight: 600; font-size: 0.95rem; border: 0; cursor: pointer; }
.btn.ghost { background: transparent; color: var(--ink); border: 1px solid var(--line); }
.depths { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 1.2rem; }
.depths a { font-size: 0.88rem; padding: 0.35rem 0.75rem; border: 1px solid var(--line); border-radius: 999px; text-decoration: none; color: var(--ink-2); background: var(--surface); }
.depths a b { color: var(--ink); }
.list-head { font: 600 0.8rem/1 var(--sans); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-3); margin: 2.5rem 0 1rem; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(18rem, 1fr)); gap: 1.25rem; padding-bottom: 3rem; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: 0.9rem; padding: 1.15rem 1.2rem; display: flex; flex-direction: column; gap: 0.45rem; }
.card h3 { font: 700 1.2rem/1.25 var(--serif); margin: 0; }
.card h3 a { color: var(--ink); text-decoration: none; }
.card h3 a:hover { color: var(--accent-ink); }
.card p { margin: 0; color: var(--ink-2); font-size: 0.95rem; }
.tags { display: flex; flex-wrap: wrap; gap: 0.35rem; }
.tag { font-size: 0.75rem; padding: 0.15rem 0.55rem; border-radius: 999px; background: var(--accent-soft); color: var(--accent-ink); text-decoration: none; }
.empty { padding: 4rem 0; color: var(--ink-2); }

/* article */
.article-head { padding-block: 2.5rem 1.25rem; }
.article-head h1 { font: 700 clamp(2rem, 4.6vw, 3rem)/1.1 var(--serif); letter-spacing: -0.02em; margin: 0.5rem 0 0.9rem; }
.article-head .dek { font-size: 1.18rem; color: var(--ink-2); margin: 0 0 1rem; }
.disclosure { font-size: 0.82rem; color: var(--ink-3); border-left: 3px solid var(--line); padding-left: 0.75rem; margin-top: 1rem; }
.depthbar { position: sticky; top: 3.5rem; z-index: 9; background: var(--bg); border-block: 1px solid var(--line); overflow-x: auto; scrollbar-width: none; }
.depthbar::-webkit-scrollbar { display: none; }
.depthbar ol { list-style: none; display: flex; gap: 0.3rem; margin: 0 auto; padding: 0.45rem 1.25rem; max-width: 72rem; white-space: nowrap; }
.depthbar a { display: block; font-size: 0.82rem; padding: 0.3rem 0.65rem; border-radius: 999px; text-decoration: none; color: var(--ink-2); }
.depthbar a.on { background: var(--ink); color: var(--bg); }
.depthbar small { opacity: 0.6; margin-left: 0.3rem; }
.tldr { background: var(--surface); border: 1px solid var(--line); border-radius: 0.9rem; padding: 1.1rem 1.3rem; margin: 1.75rem 0; }
.prose .tldr h2 { font: 700 0.8rem/1 var(--sans); letter-spacing: 0.1em; text-transform: uppercase; color: var(--accent-ink); margin: 0 0 0.6rem; }
.tldr ul { margin: 0; padding-left: 1.1rem; }
.tldr li { margin: 0.3rem 0; }
.prose { font-size: 1.08rem; }
.prose h2 { font: 700 1.75rem/1.2 var(--serif); letter-spacing: -0.01em; margin: 3rem 0 0.3rem; }
.prose h3 { font: 700 1.25rem/1.3 var(--serif); margin: 2rem 0 0.4rem; }
.prose p, .prose ul, .prose ol { margin: 0 0 1.1rem; }
.prose li { margin: 0.25rem 0; }
.prose blockquote { margin: 1.5rem 0; padding: 0.2rem 1.1rem; border-left: 3px solid var(--accent); color: var(--ink-2); }
.prose code { font: 0.88em var(--mono); background: var(--code-bg); padding: 0.1em 0.35em; border-radius: 0.3em; }
.prose pre { background: var(--code-bg); padding: 1rem 1.1rem; border-radius: 0.6rem; overflow-x: auto; font-size: 0.88rem; line-height: 1.5; }
.prose pre code { background: none; padding: 0; }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 2.5rem 0; }
.table-wrap { overflow-x: auto; margin: 1.25rem 0; border: 1px solid var(--line); border-radius: 0.6rem; }
.prose table { border-collapse: collapse; width: 100%; font-size: 0.93rem; }
.prose th, .prose td { text-align: left; padding: 0.55rem 0.75rem; border-bottom: 1px solid var(--line); vertical-align: top; }
.prose th { background: var(--surface); font-weight: 600; }
.math { overflow-x: auto; padding: 0.4rem 0; }
.level { display: inline-block; font: 600 0.72rem/1 var(--sans); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3); border: 1px solid var(--line); border-radius: 999px; padding: 0.3rem 0.6rem; margin-top: 3rem; }
.level + h2 { margin-top: 0.6rem; }
.takeaway { margin: 2.5rem 0; padding: 1.5rem 1.4rem; border-radius: 0.9rem; background: var(--accent-soft); }
.takeaway p { font: 600 1.35rem/1.35 var(--serif); margin: 0 0 0.8rem; color: var(--ink); }
.takeaway a { font-size: 0.88rem; }
.box { border: 1px solid var(--line); background: var(--surface); border-radius: 0.9rem; padding: 1.2rem 1.3rem; margin: 2rem 0; }
.prose .box h2 { margin-top: 0; font-size: 1.4rem; }
.quiz-q { margin: 1.1rem 0 1.4rem; }
.quiz-q > p { font-weight: 600; margin-bottom: 0.5rem; }
.quiz-q button { display: block; width: 100%; text-align: left; font: inherit; font-size: 0.98rem; color: var(--ink); background: var(--bg); border: 1px solid var(--line); border-radius: 0.6rem; padding: 0.55rem 0.8rem; margin: 0.35rem 0; cursor: pointer; }
.quiz-q button.right { border-color: #2f8f4e; background: color-mix(in srgb, #2f8f4e 14%, var(--bg)); }
.quiz-q button.wrong { border-color: var(--accent); background: var(--accent-soft); }
.quiz-q .why { font-size: 0.95rem; color: var(--ink-2); margin-top: 0.5rem; }
.quiz-score { font-weight: 600; }
dl.gloss dt { font-weight: 700; margin-top: 0.8rem; }
dl.gloss dd { margin: 0.1rem 0 0; color: var(--ink-2); }
details.faq { border-bottom: 1px solid var(--line); padding: 0.75rem 0; }
details.faq summary { cursor: pointer; font-weight: 600; }
details.faq p { margin: 0.5rem 0 0; color: var(--ink-2); }
ol.sources { padding-left: 1.3rem; font-size: 0.95rem; }
ol.sources li { margin: 0.45rem 0; }
ol.sources .pub { color: var(--ink-3); }
.share { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: 1.5rem 0; }
.share a, .share button { font: 600 0.85rem/1 var(--sans); padding: 0.55rem 0.85rem; border-radius: 999px; border: 1px solid var(--line); background: var(--surface); color: var(--ink); text-decoration: none; cursor: pointer; }
.related { border-top: 1px solid var(--line); margin-top: 3rem; padding-top: 1rem; }

/* footer */
.foot { border-top: 1px solid var(--line); margin-top: 4rem; padding-block: 2rem 3rem; font-size: 0.88rem; color: var(--ink-3); }
.foot .wrap { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 1rem; }
.foot nav { display: flex; flex-wrap: wrap; gap: 1rem; }
.foot a { color: var(--ink-2); }
.page h1 { font: 700 2.4rem/1.15 var(--serif); margin: 2.5rem 0 1rem; }

@media (max-width: 640px) {
  body { font-size: 17px; }
  .nav a.hide-sm { display: none; }
  .depthbar { top: 3.5rem; }
}
@media print { .top, .depthbar, .share, .foot, ins { display: none !important; } }

/* newsletter */
.nl-box { border: 1px solid var(--line); background: var(--surface); border-radius: 0.9rem; padding: 1.1rem 1.3rem; margin: 2rem 0; }
.nl-box h3 { font: 700 1.2rem/1.3 var(--serif); margin: 0 0 0.3rem; }
.nl-box p { margin: 0 0 0.7rem; color: var(--ink-2); font-size: 0.97rem; }
.nl-box form, #comment-form .row { display: flex; flex-wrap: wrap; gap: 0.5rem; align-items: center; }
.nl-box input[type=email], .signin input[type=email] { flex: 1 1 14rem; min-width: 0; font: inherit; font-size: 1rem; padding: 0.6rem 0.8rem; border: 1px solid var(--line); border-radius: 999px; background: var(--bg); color: var(--ink); }
.nl-box .msg { margin: 0.3rem 0 0; color: var(--ink); }
.fine { font-size: 0.8rem !important; color: var(--ink-3) !important; margin: 0.5rem 0 0 !important; }
/* discussion */
.discuss-head { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.like { font: 600 1rem var(--sans); border: 1px solid var(--line); background: var(--surface); color: var(--ink-2); border-radius: 999px; padding: 0.45rem 0.9rem; cursor: pointer; }
.like.on { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); }
ol.comments { list-style: none; padding: 0; margin: 0.5rem 0 1rem; }
ol.comments li { border-bottom: 1px solid var(--line); padding: 0.75rem 0; }
.c-meta { font-size: 0.82rem; color: var(--ink-3); margin-bottom: 0.2rem; }
.c-body { font-size: 0.98rem; }
.empty-c { color: var(--ink-3); font-size: 0.95rem; }
#comment-form textarea { width: 100%; font: inherit; font-size: 1rem; padding: 0.7rem 0.8rem; border: 1px solid var(--line); border-radius: 0.6rem; background: var(--surface); color: var(--ink); margin-bottom: 0.5rem; }
#comment-form .msg { font-size: 0.88rem; color: var(--ink-2); }
/* sign-in dialog */
dialog#signin-dialog { border: 1px solid var(--line); border-radius: 1rem; padding: 0; background: var(--surface); color: var(--ink); width: min(26rem, calc(100vw - 2rem)); }
dialog#signin-dialog::backdrop { background: rgba(0,0,0,.45); }
.signin { padding: 1.4rem 1.4rem 1.1rem; display: flex; flex-direction: column; gap: 0.75rem; position: relative; }
.signin h2 { font: 700 1.5rem var(--serif); margin: 0; }
.signin .why { margin: 0; color: var(--ink-2); font-size: 0.95rem; }
.signin label { display: flex; flex-direction: column; gap: 0.3rem; font-size: 0.9rem; font-weight: 600; }
.chk { flex-direction: row !important; align-items: flex-start; gap: 0.5rem !important; font-weight: 400 !important; font-size: 0.9rem; }
.chk.big { font-size: 1rem; margin: 1rem 0; display: flex; }
.signin .x { position: absolute; right: 0.6rem; top: 0.4rem; border: 0; background: none; font-size: 1.6rem; color: var(--ink-3); cursor: pointer; }
.signin .msg { margin: 0; font-size: 0.92rem; }
.toast { position: fixed; left: 50%; bottom: calc(1.5rem + env(safe-area-inset-bottom, 0px)); transform: translateX(-50%); background: var(--ink); color: var(--bg); padding: 0.7rem 1.1rem; border-radius: 999px; font-size: 0.92rem; z-index: 50; }
details.danger { margin-top: 2rem; border-top: 1px solid var(--line); padding-top: 1rem; color: var(--ink-2); }
.signin input[type=email] { flex: none; border-radius: 0.6rem; }
.brand span:last-child { white-space: nowrap; }
.nav a { white-space: nowrap; }
#discuss { margin-top: 3rem; }
.discuss-head h2 { margin: 0 !important; }
@media (max-width: 640px) {
  .nav { gap: 0.8rem; font-size: 0.88rem; }
  .nav a[href="/about/"] { display: none; }
}
.sponsor { font-size: 0.9rem; color: var(--ink-2); border: 1px dashed var(--line); border-radius: 0.6rem; padding: 0.55rem 0.8rem; margin: -0.75rem 0 1.75rem; }
.sponsor span { font: 700 0.7rem var(--sans); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3); margin-right: 0.3rem; }
.sponsor .why { float: right; font-size: 0.78rem; color: var(--ink-3); }