/* Professional Agentic Product Engineering — site styles.
   Flat 4-colour palette from krivitsky.com: navy / teal / coral / amber. */
:root {
  --navy: #2c3e50;
  --teal: #1abc9c;
  --teal-d: #16a085;
  --coral: #e74c3c;
  --amber: #f39c12;

  --bg: #f7f8fa;
  --surface: #ffffff;
  --sidebar-bg: #ffffff;
  --text: #2c3e50;
  --text-soft: #5b6b7a;
  --muted: #8a99a8;
  --border: #e4e8ee;
  --accent: var(--teal-d);
  --accent-soft: rgba(26, 188, 156, 0.12);

  /* code box stays dark in both themes (Claude-docs style) */
  --code-bg: #1f2730;
  --code-text: #d8dee6;
  --code-border: #2c3845;

  --sidebar-w: 290px;
  --topbar-h: 52px;
  --maxread: 760px;

  --font-sans: "Inter", system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  --font-head: "Playfair Display", Georgia, serif;
  --font-mono: "Geist Mono", ui-monospace, "SF Mono", Menlo, monospace;
}
[data-theme="dark"] {
  --bg: #161e26;
  --surface: #1b2530;
  --sidebar-bg: #141b22;
  --text: #e7edf2;
  --text-soft: #aab8c4;
  --muted: #76869a;
  --border: #2a3742;
  --accent: #2bd4b0;
  --accent-soft: rgba(43, 212, 176, 0.14);
  --code-bg: #11181f;
  --code-border: #232f3a;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
.skip {
  position: absolute; left: -9999px; top: 0; background: var(--navy); color: #fff;
  padding: 10px 16px; border-radius: 0 0 8px 0; z-index: 100;
}
.skip:focus { left: 0; }

/* ----------------------------------------------------------------- topbar */
/* narrow sticky top panel — brand (left) + theme toggle (right) */
.topbar {
  display: flex; position: sticky; top: 0; z-index: 50;
  height: var(--topbar-h); align-items: center; gap: 14px; padding: 0 22px;
  background: var(--bg); border-bottom: 1px solid var(--border);
}
.topbar-brand { display: flex; align-items: center; gap: 10px; color: var(--text); }
.topbar-brand img { height: 30px; width: auto; }
.topbar .sidebar-brand-text { font-family: var(--font-head); font-size: 16px; line-height: 1; white-space: nowrap; color: var(--text); font-weight: 500; }
.menu-btn, .theme-btn {
  display: grid; place-items: center; width: 40px; height: 40px; flex: none;
  border: 1px solid var(--border); border-radius: 10px; background: var(--surface);
  color: var(--text); cursor: pointer;
}
.menu-btn { display: none; }
.theme-btn { margin-left: auto; }
.theme-btn .i-moon { display: none; }
[data-theme="dark"] .theme-btn .i-sun { display: none; }
[data-theme="dark"] .theme-btn .i-moon { display: block; }

/* ---------------------------------------------------------------- sidebar */
.layout { display: flex; align-items: flex-start; }
/* desktop: sidebar pinned, scrolls independently of the content (docs style) */
.sidebar {
  width: var(--sidebar-w); flex: none;
  position: sticky; top: var(--topbar-h); align-self: flex-start;
  height: calc(100vh - var(--topbar-h)); overflow-y: auto;
  background: var(--sidebar-bg); border-right: 1px solid var(--border);
  padding: 18px 14px 40px;
}
.theme-float { position: fixed; top: 14px; right: 18px; z-index: 60; }
.sidebar-brand { display: flex; align-items: center; gap: 11px; padding: 2px 6px 18px; color: var(--text); }
.sidebar-brand img { height: 34px; width: auto; flex: none; }
.sidebar-brand-text { font-family: var(--font-head); font-size: 15px; line-height: 1.22; color: var(--text); font-weight: 500; }
.sidebar-brand-text strong { font-weight: 800; color: var(--accent); }
.nav-group { margin-bottom: 18px; }
.nav-group-title {
  margin: 0 0 6px; padding: 0 10px; font-size: 11px; letter-spacing: .09em;
  text-transform: uppercase; color: var(--muted); font-weight: 700;
}
.nav ul { list-style: none; margin: 0; padding: 0; }
.nav li a {
  display: flex; align-items: center; gap: 10px; padding: 7px 10px; margin: 1px 0;
  border-radius: 9px; color: var(--text-soft); font-size: 14.5px; line-height: 1.3;
}
.nav li a:hover { background: var(--accent-soft); color: var(--text); text-decoration: none; }
.nav li a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.nav-num {
  flex: none; display: grid; place-items: center; width: 24px; height: 24px;
  font-size: 11px; font-weight: 700; border-radius: 7px;
  background: var(--navy); color: #fff;
}
.nav li a.active .nav-num { background: var(--teal-d); }
[data-theme="dark"] .nav-num { background: #34495e; }
.overlay {
  position: fixed; inset: 0; background: rgba(20,30,40,.5); z-index: 45;
  opacity: 0; pointer-events: none; transition: opacity .2s;
}

/* ------------------------------------------------------------------- main */
.main { flex: 1; min-width: 0; min-height: 100vh; }
.content {
  max-width: var(--maxread); margin: 0 auto; padding: 40px 28px 12px;
  overflow-wrap: break-word;
}
.eyebrow {
  font-size: 12.5px; letter-spacing: .08em; text-transform: uppercase;
  color: var(--teal-d); font-weight: 700; margin: 0 0 6px;
}
[data-theme="dark"] .eyebrow { color: var(--accent); }
.hero-cta .eyebrow { margin-bottom: 14px; }

/* typography */
.content h1, .content h2, .content h3, .content h4 {
  font-family: var(--font-head); line-height: 1.2; color: var(--text);
  scroll-margin-top: calc(var(--topbar-h) + 16px);
}
.content h1, .page-title { font-size: 2.3rem; font-weight: 800; margin: .1em 0 .6em; letter-spacing: -.01em; }
.content h2 { font-size: 1.7rem; font-weight: 700; margin: 2.2em 0 .5em; padding-top: .3em; }
.content h3 { font-size: 1.28rem; font-weight: 700; margin: 1.8em 0 .4em; font-family: var(--font-sans); }
.content h4 { font-size: 1.06rem; margin: 1.4em 0 .3em; font-family: var(--font-sans); }
.content p, .content li { color: var(--text); }
.content a { font-weight: 500; border-bottom: 1px solid transparent; }
.content a:hover { border-bottom-color: currentColor; text-decoration: none; }
.content strong { color: var(--text); font-weight: 700; }
.content em { color: var(--text-soft); }
.content hr { border: 0; border-top: 1px solid var(--border); margin: 2.4em 0; }
.content ul, .content ol { padding-left: 1.3em; }
.content li { margin: .3em 0; }
.content li::marker { color: var(--teal-d); }

/* blockquote = the Instead / Prefer pairs */
.content blockquote {
  margin: 1.1em 0; padding: 4px 18px; border-left: 4px solid var(--teal);
  background: var(--accent-soft); border-radius: 0 12px 12px 0;
}
.content blockquote p { margin: .55em 0; color: var(--text); }
.content .lbl-instead { color: var(--coral); }
.content .lbl-prefer { color: var(--teal-d); }
[data-theme="dark"] .content .lbl-instead { color: #ff6f61; }
[data-theme="dark"] .content .lbl-prefer { color: var(--accent); }

/* inline code */
.content code {
  font-family: var(--font-mono); font-size: .87em;
  background: var(--accent-soft); color: var(--teal-d);
  padding: .12em .42em; border-radius: 6px;
}
[data-theme="dark"] .content code { color: var(--accent); }

/* tables */
.content table {
  width: 100%; border-collapse: collapse; margin: 1.4em 0; font-size: 15px;
  display: block; overflow-x: auto;
}
.content th, .content td { border: 1px solid var(--border); padding: 9px 13px; text-align: left; vertical-align: top; }
.content th { background: var(--accent-soft); font-weight: 700; color: var(--text); }
.content tr:nth-child(even) td { background: color-mix(in srgb, var(--surface) 60%, var(--bg)); }

/* ------------------------------------------------- code box (Claude style) */
.codebox {
  position: relative; margin: 1.3em 0; border-radius: 14px;
  background: var(--code-bg); border: 1px solid var(--code-border);
  box-shadow: 0 2px 10px rgba(20,30,40,.10); overflow: hidden;
}
.codebox::before {
  content: attr(data-lang); position: absolute; top: 0; left: 0;
  font: 600 10.5px var(--font-sans); letter-spacing: .07em; text-transform: uppercase;
  color: #8a99a8; padding: 9px 14px;
}
.codebox pre {
  margin: 0; padding: 34px 18px 18px; overflow-x: auto;
  font-family: var(--font-mono); font-size: 13.5px; line-height: 1.65;
  color: var(--code-text);
}
.codebox code { background: none; color: inherit; padding: 0; font-size: inherit; }
.codebox .copy {
  position: absolute; top: 8px; right: 8px; z-index: 2;
  display: inline-flex; align-items: center; gap: 5px;
  background: rgba(255,255,255,.06); color: #c2cdd8;
  border: 1px solid rgba(255,255,255,.12); border-radius: 8px;
  padding: 5px 9px; font: 600 11.5px var(--font-sans); cursor: pointer;
  opacity: .45; transition: opacity .15s, background .15s;
}
.codebox:hover .copy, .codebox .copy:focus { opacity: 1; }
.codebox .copy:hover { background: rgba(255,255,255,.13); }
.codebox .copy.copied { color: var(--teal); border-color: var(--teal); }
.codebox .copy span { line-height: 1; }

/* highlight.js — pastel theme tuned to the dark code box */
.hljs-attr, .hljs-attribute, .hljs-property { color: #82aaff; }
.hljs-string, .hljs-meta-string { color: #e0a06a; }
.hljs-keyword, .hljs-built_in, .hljs-literal { color: #c792ea; }
.hljs-number { color: #f78c6c; }
.hljs-comment, .hljs-quote { color: #6b7a8a; font-style: italic; }
.hljs-title, .hljs-section, .hljs-name { color: #82d2c0; }
.hljs-bullet, .hljs-symbol, .hljs-variable, .hljs-template-variable { color: #f7c873; }
.hljs-deletion { color: var(--coral); }
.hljs-addition { color: var(--teal); }

/* mermaid */
.mermaid {
  margin: 1.4em 0; padding: 18px; text-align: center;
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
}

/* ------------------------------------------------------------- tier cards */
.tier-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(232px, 1fr)); gap: 14px; margin: 1.4em 0 2em; }
.tier-card {
  display: flex; flex-direction: column; gap: 6px; padding: 16px 18px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  color: var(--text); transition: transform .12s, border-color .12s, box-shadow .12s;
}
.tier-card:hover { transform: translateY(-2px); border-color: var(--teal); box-shadow: 0 6px 18px rgba(26,188,156,.14); text-decoration: none; }
.tier-card-n {
  align-self: flex-start; font: 700 12px var(--font-sans); letter-spacing: .05em;
  background: var(--navy); color: #fff; padding: 3px 9px; border-radius: 999px;
}
[data-theme="dark"] .tier-card-n { background: var(--teal-d); }
.tier-card-name { font-family: var(--font-head); font-size: 1.12rem; font-weight: 700; }
.tier-card-blurb { font-size: 13.5px; color: var(--text-soft); line-height: 1.5; }

/* ------------------------------------------------------------------ pager */
.pager {
  max-width: var(--maxread); margin: 28px auto 0; padding: 0 28px;
  display: flex; gap: 14px; justify-content: space-between;
}
.pager a {
  display: flex; flex-direction: column; gap: 2px; flex: 1; max-width: 48%;
  padding: 14px 18px; border: 1px solid var(--border); border-radius: 14px;
  background: var(--surface); color: var(--text);
}
.pager a:hover { border-color: var(--teal); text-decoration: none; }
.pager-next { text-align: right; align-items: flex-end; }
.pager span { font-size: 12.5px; color: var(--muted); }
.pager strong { font-size: 15px; }

/* ----------------------------------------------------------------- footer */
.creditrow { display: flex; align-items: center; gap: 16px; }
.cred-logo { height: 44px; width: auto; flex: none; }
.cred-text p { margin: 2px 0; font-size: 14px; color: var(--text-soft); }
.cred-text .buildmeta { font-size: 12px; color: var(--muted); margin-top: 5px; }
.cred-text .buildmeta a { color: var(--muted); border-bottom: 1px dotted var(--border); }
.hero-credit { margin: 4px 0 26px; padding-bottom: 18px; border-bottom: 1px solid var(--border); }
.site-footer {
  max-width: var(--maxread); margin: 48px auto 0; padding: 26px 28px 50px;
  border-top: 1px solid var(--border);
}
.footer-links { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 8px 18px; margin-top: 16px; font-size: 13px; }
.footer-links a { color: var(--muted); border-bottom: 1px dotted var(--border); }
.footer-links a:hover { color: var(--accent); }

/* home hero */
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.hero-banner {
  width: 100%; height: auto; border-radius: 16px; display: block;
  margin: 4px 0 22px; box-shadow: 0 6px 26px rgba(20, 30, 40, .20);
}
/* inline figures (e.g. the nested-loops diagram) */
.content p img { display: block; max-width: 100%; height: auto; margin: 1.6em auto; }
.learn-callout {
  background: var(--accent-soft);
  border: 1px solid color-mix(in srgb, var(--teal) 38%, transparent);
  border-radius: 14px; padding: 16px 22px; margin: 0 0 22px;
}
.learn-callout p { margin: 4px 0; color: var(--text); }
.learn-callout-title { font-weight: 700; font-size: 1.06rem; }
.learn-callout-link { font-weight: 700; }

/* ------------------------------------------------------------ responsive */
@media (max-width: 940px) {
  body { font-size: 16px; }
  .topbar { display: flex; }
  .menu-btn { display: grid; }
  .topbar-brand span { display: none; }
  .sidebar {
    position: fixed; top: 0; left: 0; height: 100vh; overflow-y: auto; z-index: 50;
    transform: translateX(-100%); transition: transform .24s ease; box-shadow: 0 0 40px rgba(0,0,0,.18);
  }
  .sidebar.open { transform: translateX(0); }
  .overlay.show { opacity: 1; pointer-events: auto; }
  .content { padding: 26px 20px 12px; }
  .content h1, .page-title { font-size: 1.85rem; }
  .content h2 { font-size: 1.42rem; }
  .pager { padding: 0 20px; }
  .pager a { max-width: 49%; }
}
@media (max-width: 520px) {
  .tier-cards { grid-template-columns: 1fr; }
  .creditrow { flex-direction: column; text-align: center; }
}