:root {
  --bg: #f5f5f7;
  --surface: #ffffff;
  --ink: #1d1d1f;
  --soft: #515154;
  --faint: #86868b;
  --line: #d2d2d7;
  --line-soft: #e8e8ed;
  --night: #211929;
  --violet: #7259d9;
  --violet-soft: #eeeafd;
  --green: #187a58;
  --green-soft: #e7f5ef;
  --amber: #9b5c14;
  --amber-soft: #fbf2e6;
  --red: #b4472d;
  --red-soft: #fff0ec;
  --blue: #1264a3;
  --blue-soft: #eaf4ff;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", "PingFang SC", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --mono: ui-monospace, "SFMono-Regular", SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  --type-display: clamp(40px, 3.8vw, 50px);
  --type-section: 30px;
  --type-body: 16px;
  --type-small: var(--type-body);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: var(--type-body);
  line-height: 1.72;
  letter-spacing: -0.011em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
a { color: var(--violet); text-underline-offset: 3px; }

.site-nav {
  position: sticky;
  top: 0;
  z-index: 30;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 max(24px, calc((100vw - 1152px) / 2));
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  background: rgba(245, 245, 247, 0.88);
  backdrop-filter: saturate(180%) blur(20px);
}
.site-nav a { color: var(--ink); text-decoration: none; }
.brand { font-size: var(--type-body); font-weight: 650; letter-spacing: -0.025em; }
.brand span { color: var(--violet); }
.all-notes { font-size: var(--type-small); font-weight: 600; color: var(--soft) !important; }
.all-notes:hover { color: var(--ink) !important; }

.page { width: min(1152px, calc(100% - 64px)); margin: 0 auto; padding: 0 0 96px; }
.article-hero {
  position: relative;
  width: 840px;
  margin-left: auto;
  padding: 52px 0 36px;
  border-bottom: 1px solid var(--line);
  background: transparent;
  color: var(--ink);
}
.article-hero::before, .article-hero::after { display: none; }
.article-hero.agent, .article-hero.training { background: transparent; }
.article-kicker {
  position: relative;
  margin-bottom: 14px;
  font-size: var(--type-small);
  font-weight: 700;
  letter-spacing: 0.17em;
  text-transform: uppercase;
  color: var(--violet);
}
.article-hero.agent .article-kicker { color: var(--green); }
.article-hero.training .article-kicker { color: var(--amber); }
.article-hero h1 {
  position: relative;
  max-width: 840px;
  margin: 0;
  font-size: var(--type-display);
  font-weight: 650;
  line-height: 1.06;
  letter-spacing: -0.045em;
}
.article-hero h1 span { display: block; margin-bottom: 6px; font-size: var(--type-body); letter-spacing: -0.015em; color: var(--faint); }
.article-hero p {
  position: relative;
  max-width: 720px;
  margin: 14px 0 0;
  color: var(--soft);
  font-size: var(--type-body);
  line-height: 1.55;
}

.article-meta {
  width: min(820px, calc(100% - 32px));
  margin: 34px auto 0;
  display: flex;
  flex-wrap: wrap;
  gap: 9px;
}
.article-meta span {
  padding: 6px 11px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--faint);
  font-size: var(--type-small);
  font-weight: 650;
  letter-spacing: 0.08em;
}

.reading-layout {
  width: 100%;
  margin: 38px auto 0;
  display: grid;
  grid-template-columns: 240px minmax(0, 840px);
  gap: 72px;
  align-items: stretch;
}
.article-toc { min-width: 0; align-self: stretch; border-right: 1px solid var(--line); }
.toc-card {
  position: sticky;
  top: 84px;
  max-height: calc(100vh - 108px);
  overflow: auto;
  padding: 10px 24px 12px 0;
  background: transparent;
}
.toc-eyebrow { color: var(--violet); font-size: var(--type-small); font-weight: 750; letter-spacing: 0.15em; text-transform: uppercase; }
.toc-title { margin-top: 7px; font-size: var(--type-body); font-weight: 700; letter-spacing: -0.02em; }
.toc-summary { display: flex; justify-content: space-between; gap: 12px; margin: 14px 0 17px; padding-bottom: 15px; border-bottom: 1px solid var(--line-soft); color: var(--faint); font-size: var(--type-small); }
.toc-list { position: relative; list-style: none; margin: 0; padding: 0; counter-reset: toc; }
.toc-list::before { content: ""; position: absolute; left: 13px; top: 16px; bottom: 16px; width: 1px; background: var(--line-soft); }
.toc-list li { position: relative; margin: 0; counter-increment: toc; }
.toc-list a { display: grid; grid-template-columns: 28px 1fr; gap: 10px; align-items: start; padding: 8px 0; color: var(--faint); text-decoration: none; transition: color 0.18s; }
.toc-list a:hover { color: var(--ink); }
.toc-list .toc-n { position: relative; z-index: 1; width: 29px; height: 29px; display: grid; place-items: center; border: 0; background: var(--bg); color: var(--faint); font-size: var(--type-small); font-weight: 750; }
.toc-list a.is-active { color: var(--ink); }
.toc-list a.is-active .toc-n { background: var(--bg); color: var(--violet); box-shadow: inset 3px 0 0 var(--violet); }
.toc-list a.is-active .toc-text { font-weight: 700; }
.toc-list .toc-text { padding-top: 3px; font-size: var(--type-small); font-weight: 600; line-height: 1.45; }
.toc-foot { display: flex; align-items: center; gap: 8px; margin-top: 16px; padding-top: 14px; border-top: 1px solid var(--line-soft); color: var(--faint); font-size: var(--type-small); }
.toc-foot::before { content: ""; width: 18px; height: 1px; background: var(--violet); }
.article-body { width: 100%; margin: 0; min-width: 0; align-self: start; }
.article-body > section {
  padding: 50px 0 12px;
  border-top: 1px solid var(--line-soft);
  scroll-margin-top: 76px;
}
.article-body > section:first-of-type { padding-top: 0; border-top: 0; }
.article-body h2 {
  margin: 0 0 24px;
  font-size: var(--type-section);
  font-weight: 650;
  line-height: 1.14;
  letter-spacing: -0.035em;
}
.article-body h2 .ey { color: var(--faint); font-size: var(--type-small); margin-right: 8px; }
.article-body h3 {
  margin: 38px 0 12px;
  font-size: var(--type-body);
  font-weight: 650;
  line-height: 1.25;
  letter-spacing: -0.025em;
}
.article-body h4 { margin: 28px 0 8px; font-size: var(--type-body); font-weight: 700; color: var(--soft); }
.article-body p { margin: 0 0 18px; }
.article-body .lead { color: var(--soft); font-size: var(--type-body); line-height: 1.72; }
.article-body strong, .article-body b { font-weight: 650; }
.article-body ul, .article-body ol { margin: 0 0 20px; padding-left: 24px; }
.article-body li { margin: 8px 0; }
.article-body .term { font-weight: 650; border-bottom: 2px solid var(--violet-soft); }
.article-body .path { font-family: var(--mono); font-size: var(--type-small); padding: 2px 7px; border: 1px solid var(--line); border-radius: 6px; background: #ececf0; }

.article-deck {
  margin: 0 0 34px;
  color: var(--soft);
  font-size: var(--type-body);
  font-weight: 450;
  line-height: 1.55;
  letter-spacing: -0.02em;
}
.article-body > .article-meta { width: auto; margin: 0 0 38px; }
.thesis {
  margin: 30px 0;
  padding: 28px;
  border-radius: 18px;
  background: var(--night);
  color: #f5f5f7;
  font-size: var(--type-body);
  font-weight: 520;
  line-height: 1.42;
  letter-spacing: -0.025em;
}
.thesis strong { color: #b8a9ff; }

.part {
  margin: 92px 0 16px;
  padding-top: 32px;
  border-top: 1px solid var(--line);
}
.part .pn, .part .ps { color: var(--faint); font-size: var(--type-small); font-weight: 650; letter-spacing: 0.12em; }
.part .pt { font-size: var(--type-section); font-weight: 650; line-height: 1.16; letter-spacing: -0.035em; }
.part + section { border-top: 0; padding-top: 24px; }

figure {
  margin: 32px 0;
  padding: 20px 20px 10px;
  overflow: hidden;
  border: 1px solid var(--line-soft);
  border-radius: 20px;
  background: var(--surface);
  box-shadow: 0 18px 44px -40px rgba(0, 0, 0, 0.45);
}
figure svg { display: block; width: 100%; height: auto; }
figcaption { padding: 11px 4px 4px; color: var(--faint); font-size: var(--type-small); text-align: center; }

.callout, .why, .prompt {
  margin: 24px 0;
  padding: 18px 20px;
  border: 1px solid;
  border-radius: 16px;
  font-size: var(--type-body);
}
.callout p:last-child, .why p:last-child, .prompt p:last-child { margin-bottom: 0; }
.callout .h, .why .h, .prompt .h { display: block; margin-bottom: 6px; font-weight: 650; }
.key { border-color: #d9d0fc; background: var(--violet-soft); }
.key .h, .why .h { color: #5e45c0; }
.why { border-color: #d9d0fc; border-left: 4px solid var(--violet); background: #f8f6ff; }
.tip { border-color: #c7dff5; background: var(--blue-soft); }
.tip .h { color: var(--blue); }
.warn { border-color: #f0c3b8; background: var(--red-soft); }
.warn .h { color: var(--red); }
.ai-box, .prompt { border-color: #ead2b6; background: var(--amber-soft); }
.ai-box .h, .prompt .h { color: var(--amber); }
.prompt .say { margin-top: 8px; padding: 13px 15px; border: 1px dashed #dcbf9c; border-radius: 10px; background: #fff; }
.prompt .say.mono { white-space: pre-wrap; font-family: var(--mono); font-size: var(--type-small); line-height: 1.65; }

.scroller { overflow-x: auto; margin: 24px 0; -webkit-overflow-scrolling: touch; }
.ct {
  width: 100%;
  min-width: 640px;
  border-collapse: separate;
  border-spacing: 0;
  overflow: hidden;
  border: 1px solid var(--line-soft);
  border-radius: 14px;
  background: var(--surface);
  font-size: var(--type-small);
}
.ct th, .ct td { padding: 13px 14px; border-bottom: 1px solid var(--line-soft); text-align: left; vertical-align: top; }
.ct th { background: #f0f0f2; color: var(--soft); font-size: var(--type-small); font-weight: 650; }
.ct td:first-child { font-weight: 650; }
.ct tr:last-child td { border-bottom: 0; }
.ct .y { color: var(--green); font-weight: 650; }
.ct .n { color: var(--red); font-weight: 650; }

.grid2, .modules, .before-after, .decision-split, .failure-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 24px 0; }
.five { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; margin: 24px 0; }
.five .c, .failure, .ba, .decision-split > div {
  padding: 18px;
  border: 1px solid var(--line-soft);
  border-radius: 14px;
  background: var(--surface);
}
.five .c b { display: block; color: var(--green); }
.five .c .d { margin-top: 4px; color: var(--soft); font-size: var(--type-small); }
.failure:last-child { grid-column: 1 / -1; }
.failure .code, .ba .label { color: var(--faint); font-size: var(--type-small); font-weight: 700; letter-spacing: 0.12em; }
.failure h3, .decision-split h3 { margin-top: 10px; }
.failure p, .ba p { color: var(--soft); font-size: var(--type-body); }
.ba.bad { border-top: 3px solid var(--red); }
.ba.good { border-top: 3px solid var(--green); }

.formula, .eval-matrix { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; margin: 26px 0; overflow: hidden; border: 1px solid var(--line); border-radius: 16px; background: var(--line); }
.formula div, .eval-card { padding: 18px; background: var(--surface); }
.formula b, .eval-card b { display: block; color: #5e45c0; font-size: var(--type-body); font-weight: 700; }
.formula span, .eval-card span { display: block; margin-top: 6px; color: var(--soft); font-size: var(--type-small); line-height: 1.5; }
.spec-stack, .mini, .feat { display: grid; gap: 10px; margin: 24px 0; }
.spec-layer { display: grid; grid-template-columns: 42px 150px 1fr; gap: 14px; padding: 15px 17px; border: 1px solid var(--line-soft); border-radius: 12px; background: var(--surface); }
.spec-layer i { color: var(--violet); font-style: normal; }
.spec-layer span { color: var(--soft); font-size: var(--type-small); }
.mini .m, .feat .row, .road .r { padding: 15px 17px; border: 1px solid var(--line-soft); border-radius: 13px; background: var(--surface); }
.mini .m { display: grid; grid-template-columns: 160px 1fr; gap: 12px; }
.feat .row { display: grid; grid-template-columns: 170px 1fr; gap: 14px; }
.feat .name { font-weight: 650; }
.feat .sub, .feat .where { display: block; color: var(--faint); font-size: var(--type-small); }

.stage { display: flex; align-items: center; gap: 13px; margin: 30px 0 8px; padding: 14px 16px; border-left: 4px solid var(--green); border-radius: 10px; background: linear-gradient(90deg, var(--green-soft), transparent); }
.stage .n { width: 38px; height: 38px; display: grid; place-items: center; flex: 0 0 auto; border-radius: 10px; background: var(--green); color: white; font-size: var(--type-small); font-weight: 700; }
.stage .t { font-size: var(--type-body); font-weight: 650; }
.stage .t small { display: block; color: var(--soft); font-size: var(--type-small); }
.stage .five-tag { margin-left: auto; padding: 3px 10px; border-radius: 999px; background: var(--green-soft); color: var(--green); font-size: var(--type-small); font-weight: 650; }

.steps, .road { margin: 24px 0; }
.road { display: grid; gap: 10px; }
.road .r { display: grid; grid-template-columns: 180px 1fr; gap: 16px; }
.road .badge { display: inline-block; padding: 3px 8px; border-radius: 999px; background: var(--violet-soft); color: #5e45c0; font-size: var(--type-small); font-weight: 700; }
.road .mt { font-weight: 650; }
.road .md { color: var(--soft); font-size: var(--type-small); }

.case-head { margin: 32px 0 22px; padding: 20px 22px; border-left: 3px solid var(--violet); background: var(--violet-soft); }
.case-head b { display: block; font-size: var(--type-body); font-weight: 700; }
.case-head span { display: block; margin-top: 5px; color: var(--soft); font-size: var(--type-small); }
.prompt-long { margin: 28px 0; overflow: hidden; border-radius: 18px; background: var(--night); color: #ece8ef; }
.prompt-long .prompt-title { display: flex; justify-content: space-between; gap: 20px; padding: 14px 18px; border-bottom: 1px solid rgba(255, 255, 255, 0.14); color: #aaa0ad; font-size: var(--type-small); font-weight: 700; letter-spacing: 0.12em; }
.prompt-long pre { margin: 0; padding: 24px; white-space: pre-wrap; overflow-wrap: anywhere; font: var(--type-body)/1.72 var(--mono); }
.prompt-long .tag { color: #b8a9ff; }
.prompt-long .note { color: #91c9ae; }
.article-pagination {
  width: min(840px, calc(100% - 32px));
  margin: 88px 0 0 auto;
  padding-top: 26px;
  border-top: 1px solid var(--line);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
}
.page-link {
  display: flex;
  min-height: 118px;
  flex-direction: column;
  justify-content: space-between;
  padding: 18px;
  border: 1px solid var(--line-soft);
  border-radius: 16px;
  background: var(--surface);
  color: var(--ink);
  text-decoration: none;
  transition: transform 0.18s, box-shadow 0.18s;
}
.page-link:hover { transform: translateY(-3px); box-shadow: 0 18px 40px -34px rgba(0, 0, 0, 0.5); }
.page-link small { color: var(--faint); font-size: var(--type-small); font-weight: 650; letter-spacing: 0.1em; text-transform: uppercase; }
.page-link b { font-size: var(--type-body); font-weight: 650; line-height: 1.3; }
.page-link.next { text-align: right; }

.article-footer { width: min(840px, calc(100% - 32px)); margin: 54px 0 0 auto; color: var(--faint); font-size: var(--type-small); text-align: center; }
.to-top { position: fixed; right: 22px; bottom: 22px; width: 42px; height: 42px; border: 0; border-radius: 50%; background: var(--ink); color: white; cursor: pointer; opacity: 0; pointer-events: none; transition: opacity 0.2s; }
.to-top.show { opacity: 1; pointer-events: auto; }

@media (max-width: 1020px) {
  .article-hero { width: min(840px, 100%); margin-inline: auto; }
  .reading-layout { width: min(840px, calc(100% - 32px)); display: block; }
  .article-toc { margin-bottom: 42px; border-right: 0; }
  .toc-card { position: relative; top: auto; max-height: none; padding: 0 0 22px; border-right: 0; border-bottom: 1px solid var(--line); }
  .toc-list { display: grid; grid-template-columns: 1fr 1fr; column-gap: 28px; }
  .toc-list::before { display: none; }
  .toc-list a { grid-template-columns: 28px 1fr; }
  .article-pagination, .article-footer { margin-left: auto; margin-right: auto; }
}

@media (max-width: 760px) {
  :root { --type-display: clamp(34px, 9.5vw, 42px); --type-section: 27px; }
  .site-nav { padding: 0 18px; }
  .all-notes { display: none; }
  .page { width: 100%; padding-top: 0; }
  .article-hero { width: calc(100% - 36px); padding: 42px 0 32px; }
  .article-meta, .article-pagination, .article-footer { width: calc(100% - 36px); }
  .reading-layout { width: calc(100% - 36px); margin-top: 34px; }
  .article-body { width: 100%; }
  .article-toc { margin-bottom: 36px; }
  .toc-list { grid-template-columns: 1fr; }
  .thesis { padding: 22px; }
  .grid2, .modules, .before-after, .decision-split, .failure-grid { grid-template-columns: 1fr; }
  .failure:last-child { grid-column: auto; }
  .five { grid-template-columns: 1fr 1fr; }
  .formula, .eval-matrix { grid-template-columns: 1fr 1fr; }
  .spec-layer { grid-template-columns: 34px 1fr; }
  .spec-layer span { grid-column: 2; }
  .mini .m, .feat .row, .road .r { grid-template-columns: 1fr; }
  .stage .five-tag { display: none; }
  .scroller { margin-inline: -18px; padding-inline: 18px; }
  .article-pagination { grid-template-columns: 1fr; }
  .page-link.next { text-align: left; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .page-link, .to-top { transition: none; }
}