/* ============================================================
   Shared design system for the AI Engineering knowledge hub
   Used by the hub (/ai/) and every topic page (/ai/<topic>/).
   ============================================================ */
:root {
  --bg: #ffffff;
  --bg-soft: #f6f8fa;
  --bg-card: #ffffff;
  --border: #e2e6eb;
  --text: #1a1f26;
  --text-soft: #5a6472;
  --accent: #6b46e5;
  --accent-2: #0ea5a4;
  --accent-soft: #efeaff;
  --code-bg: #0f1524;
  --code-text: #e6e9f0;
  --shadow: 0 1px 3px rgba(20,25,35,.06), 0 8px 24px rgba(20,25,35,.06);
  --radius: 14px;
  --maxw: 1000px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c1017; --bg-soft: #11161f; --bg-card: #141a24; --border: #232b38;
    --text: #e8ecf3; --text-soft: #98a2b3; --accent: #a78bfa; --accent-2: #2dd4bf;
    --accent-soft: #1e1b34; --code-bg: #0a0e17; --code-text: #e6e9f0;
    --shadow: 0 1px 3px rgba(0,0,0,.4), 0 12px 32px rgba(0,0,0,.4);
  }
}
/* Explicit theme overrides chosen from the reading widget - win over the media query */
:root[data-theme="light"] {
  --bg:#fff; --bg-soft:#f6f8fa; --bg-card:#fff; --border:#e2e6eb;
  --text:#1a1f26; --text-soft:#5a6472; --accent:#6b46e5; --accent-2:#0ea5a4;
  --accent-soft:#efeaff; --code-bg:#0f1524; --code-text:#e6e9f0;
}
:root[data-theme="dark"] {
  --bg:#0c1017; --bg-soft:#11161f; --bg-card:#141a24; --border:#232b38;
  --text:#e8ecf3; --text-soft:#98a2b3; --accent:#a78bfa; --accent-2:#2dd4bf;
  --accent-soft:#1e1b34; --code-bg:#0a0e17; --code-text:#e6e9f0;
}
:root[data-theme="sepia"] {
  --bg:#f4ecd8; --bg-soft:#ece0c4; --bg-card:#f8f1e0; --border:#d9c9a3;
  --text:#3b2f1c; --text-soft:#6b5b42; --accent:#9a6a2f; --accent-2:#4f7a4f;
  --accent-soft:#ecdcbf; --code-bg:#2b2416; --code-text:#f0e6d0;
}
:root[data-theme="contrast"] {
  --bg:#000; --bg-soft:#0a0a0a; --bg-card:#000; --border:#ffffff;
  --text:#fff; --text-soft:#ffe600; --accent:#ffff00; --accent-2:#00e5ff;
  --accent-soft:#1a1a00; --code-bg:#000; --code-text:#fff; --shadow:0 0 0 1px #fff;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.65; -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* Nav */
nav {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: saturate(180%) blur(12px);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  border-bottom: 1px solid var(--border);
}
nav .wrap { display: flex; align-items: center; gap: 12px; min-height: 58px; flex-wrap: wrap; padding-top: 7px; padding-bottom: 7px; }
nav .brand { font-weight: 700; letter-spacing: -.02em; font-size: 1.05rem; margin-right: auto; white-space: nowrap; }
nav .brand span { color: var(--accent); }
nav .brand a { color: inherit; }
nav .brand a:hover { text-decoration: none; }
nav .links { display: flex; gap: 1px; flex-wrap: wrap; justify-content: flex-end; }
nav .links a { color: var(--text-soft); font-size: .8rem; padding: 5px 7px; border-radius: 8px; font-weight: 500; white-space: nowrap; }
nav .links a:hover { background: var(--bg-soft); color: var(--text); text-decoration: none; }
@media (max-width: 820px) { nav .links { display: none; } }

/* Language switcher */
.lang-switch { position: relative; flex: 0 0 auto; }
.lang-btn { display: inline-flex; align-items: center; gap: 5px; font-size: .8rem; font-weight: 600; color: var(--text); background: var(--bg-soft); border: 1px solid var(--border); border-radius: 8px; padding: 5px 10px; cursor: pointer; white-space: nowrap; }
.lang-btn:hover { border-color: var(--accent); }
.lang-menu { position: absolute; right: 0; top: calc(100% + 6px); background: var(--bg-card); border: 1px solid var(--border); border-radius: 10px; box-shadow: var(--shadow); padding: 6px; min-width: 132px; display: none; z-index: 60; }
.lang-menu.open { display: block; }
.lang-menu a { display: block; padding: 8px 12px; border-radius: 7px; font-size: .85rem; color: var(--text); font-weight: 500; }
.lang-menu a:hover { background: var(--bg-soft); text-decoration: none; }
.lang-menu a.active { color: var(--accent); font-weight: 700; }

/* Hero */
header.hero {
  padding: 72px 0 48px;
  background:
    radial-gradient(1200px 400px at 80% -10%, var(--accent-soft), transparent 60%),
    radial-gradient(800px 300px at 0% 10%, color-mix(in srgb, var(--accent-2) 12%, transparent), transparent 60%);
}
.kicker {
  display: inline-block; font-size: .78rem; font-weight: 700; letter-spacing: .08em;
  text-transform: uppercase; color: var(--accent); background: var(--accent-soft);
  padding: 5px 12px; border-radius: 999px;
}
header.hero h1 { font-size: clamp(2.1rem, 5vw, 3.4rem); line-height: 1.08; letter-spacing: -.03em; margin: 18px 0 14px; font-weight: 800; }
header.hero p.lede { font-size: 1.18rem; color: var(--text-soft); max-width: 720px; margin: 0 0 26px; }
.cta { display: flex; gap: 12px; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 11px 20px; border-radius: 10px; font-weight: 600; font-size: .95rem; }
.btn.primary { background: var(--accent); color: #fff; }
.btn.primary:hover { text-decoration: none; filter: brightness(1.06); }
.btn.ghost { border: 1px solid var(--border); color: var(--text); background: var(--bg-card); }
.btn.ghost:hover { text-decoration: none; border-color: var(--accent); }
.pill-row { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 14px; }
.pill { font-size: .8rem; padding: 4px 12px; border-radius: 999px; background: var(--bg-soft); border: 1px solid var(--border); color: var(--text-soft); }

/* Sections */
section { padding: 56px 0; border-top: 1px solid var(--border); }
section > .wrap > .eyebrow { font-size: .78rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; color: var(--accent-2); margin-bottom: 8px; }
section h2 { font-size: clamp(1.6rem, 3.4vw, 2.2rem); letter-spacing: -.02em; margin: 0 0 8px; font-weight: 800; }
section h3 { font-size: 1.25rem; margin: 32px 0 10px; letter-spacing: -.01em; }
section p { color: var(--text); }
.muted { color: var(--text-soft); }

/* Cards / grids */
.grid { display: grid; gap: 16px; margin-top: 24px; }
.grid.cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid.cols-3 { grid-template-columns: repeat(3, 1fr); }
@media (max-width: 720px) { .grid.cols-2, .grid.cols-3 { grid-template-columns: 1fr; } }
.card { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow); }
.card h4 { margin: 0 0 8px; font-size: 1.05rem; display: flex; align-items: center; gap: 8px; }
.card .ico { font-size: 1.3rem; }
.card p { margin: 0; color: var(--text-soft); font-size: .95rem; }

/* Table */
.table-wrap { overflow-x: auto; margin-top: 20px; border: 1px solid var(--border); border-radius: var(--radius); }
table { width: 100%; border-collapse: collapse; font-size: .93rem; min-width: 520px; }
th, td { text-align: left; padding: 12px 16px; border-bottom: 1px solid var(--border); vertical-align: top; }
th { background: var(--bg-soft); font-weight: 700; font-size: .82rem; text-transform: uppercase; letter-spacing: .04em; color: var(--text-soft); }
tr:last-child td { border-bottom: none; }
td code { background: var(--bg-soft); padding: 1px 6px; border-radius: 6px; font-size: .85em; }

/* Code */
pre { background: var(--code-bg); color: var(--code-text); padding: 18px 20px; border-radius: 12px; overflow-x: auto; font-size: .86rem; line-height: 1.6; border: 1px solid rgba(255,255,255,.06); }
code { font-family: "SF Mono", ui-monospace, "Cascadia Code", Menlo, Consolas, monospace; }
pre code { color: inherit; }
.copy-btn { position: absolute; top: 8px; right: 8px; font-size: .72rem; font-weight: 700; padding: 4px 10px; border-radius: 7px; border: 1px solid rgba(255,255,255,.18); background: rgba(255,255,255,.08); color: #e6e9f0; cursor: pointer; opacity: .7; transition: opacity .15s, background .15s; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; }
pre:hover .copy-btn { opacity: 1; }
.copy-btn:hover { background: rgba(255,255,255,.16); }
.copy-btn.copied { background: #0ea5a4; color: #fff; border-color: transparent; }

/* Mermaid diagram - fixed light panel so it is readable under every page theme */
.diagram { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; margin-top: 20px; overflow-x: auto; box-shadow: var(--shadow); }
.diagram .cap { font-size: .85rem; color: var(--text-soft); margin-bottom: 10px; font-weight: 600; }
.mermaid { display: flex; justify-content: center; min-width: 480px; background: #ffffff; border: 1px solid #e6e8ee; border-radius: 12px; padding: 18px 14px; }

/* Steps 0-100 */
.steps { margin-top: 24px; position: relative; }
.step { display: flex; gap: 18px; padding: 6px 0 22px; position: relative; }
.step:not(:last-child)::before { content: ""; position: absolute; left: 19px; top: 40px; bottom: -4px; width: 2px; background: var(--border); }
.step .num { flex: 0 0 40px; height: 40px; width: 40px; border-radius: 50%; display: grid; place-items: center; font-weight: 800; font-size: .82rem; background: var(--accent-soft); color: var(--accent); border: 1px solid var(--border); z-index: 1; }
.step .body h4 { margin: 8px 0 4px; font-size: 1.02rem; }
.step .body p { margin: 0; color: var(--text-soft); font-size: .94rem; }
.step .body .tag { display: inline-block; font-size: .72rem; font-weight: 700; color: var(--accent-2); text-transform: uppercase; letter-spacing: .05em; }

/* Case studies */
.case { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow); margin-top: 20px; }
.case .hd { display: flex; align-items: center; gap: 12px; margin-bottom: 6px; }
.case .hd .badge { font-size: 1.6rem; }
.case .hd h3 { margin: 0; }
.case .role { font-size: .82rem; color: var(--text-soft); font-weight: 600; }
.case ul { margin: 12px 0 0; padding-left: 20px; color: var(--text-soft); }
.case ul li { margin: 6px 0; }
.case .outcome { margin-top: 14px; padding: 12px 16px; border-radius: 10px; background: var(--accent-soft); font-size: .92rem; border-left: 3px solid var(--accent); }

.callout { margin-top: 20px; padding: 16px 20px; border-radius: 12px; background: var(--bg-soft); border-left: 4px solid var(--accent-2); }
.callout strong { color: var(--text); }

footer { padding: 40px 0 60px; border-top: 1px solid var(--border); color: var(--text-soft); font-size: .88rem; text-align: center; }
footer a { color: var(--text-soft); }

/* ---- Hub landing page ---- */
.group-title { font-size: 1.35rem; font-weight: 800; letter-spacing: -.01em; margin: 40px 0 4px; display: flex; align-items: center; gap: 10px; }
.group-sub { color: var(--text-soft); margin: 0 0 8px; font-size: .95rem; }
.topic-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 20px; }
@media (max-width: 860px) { .topic-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 560px) { .topic-grid { grid-template-columns: 1fr; } }
.topic-card { position: relative; display: flex; flex-direction: column; gap: 6px; background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow); transition: transform .14s ease, border-color .14s ease; }
.topic-card:hover { transform: translateY(-3px); border-color: var(--accent); text-decoration: none; }
.topic-card .ico { font-size: 1.7rem; }
.topic-card h4 { margin: 4px 0 2px; font-size: 1.06rem; color: var(--text); letter-spacing: -.01em; }
.topic-card p { margin: 0; color: var(--text-soft); font-size: .9rem; line-height: 1.5; }
.topic-card .go { margin-top: auto; padding-top: 10px; font-size: .82rem; font-weight: 700; color: var(--accent); }
.status { position: absolute; top: 16px; right: 16px; font-size: .66rem; font-weight: 800; letter-spacing: .05em; text-transform: uppercase; padding: 3px 8px; border-radius: 999px; }
.status.live { background: color-mix(in srgb, var(--accent-2) 18%, transparent); color: var(--accent-2); }

/* Floating reading-settings widget (markup injected by app.js) */
.a11y-fab { position: fixed; right: 20px; bottom: 20px; z-index: 200; }
.a11y-toggle { height: 56px; width: 56px; border-radius: 50%; border: 2px solid var(--bg); background: var(--accent); color: #fff; font-weight: 800; font-size: 1.15rem; cursor: pointer; box-shadow: 0 6px 20px rgba(0,0,0,.25); display: grid; place-items: center; transition: transform .15s ease; line-height: 1; }
.a11y-toggle:hover { transform: scale(1.07); }
.a11y-toggle:focus-visible { outline: 3px solid var(--accent-2); outline-offset: 2px; }
.a11y-panel { position: absolute; right: 0; bottom: 68px; width: 264px; background: var(--bg-card); border: 1px solid var(--border); border-radius: 16px; box-shadow: var(--shadow); padding: 16px; display: none; }
.a11y-panel.open { display: block; }
.a11y-panel h5 { margin: 0 0 8px; font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--text-soft); }
.a11y-row { display: flex; gap: 8px; align-items: center; margin-bottom: 16px; }
.a11y-btn { flex: 1; padding: 10px 0; border-radius: 10px; border: 1px solid var(--border); background: var(--bg-soft); color: var(--text); font-weight: 700; cursor: pointer; font-size: .95rem; }
.a11y-btn:hover { border-color: var(--accent); }
.a11y-size { min-width: 54px; text-align: center; font-variant-numeric: tabular-nums; font-size: .85rem; color: var(--text-soft); font-weight: 700; }
.a11y-themes { display: grid; grid-template-columns: repeat(2,1fr); gap: 8px; margin-bottom: 14px; }
.a11y-theme { padding: 9px 8px; border-radius: 10px; border: 1px solid var(--border); cursor: pointer; font-size: .82rem; font-weight: 600; color: var(--text); background: var(--bg-soft); display: flex; align-items: center; gap: 7px; }
.a11y-theme:hover { border-color: var(--accent); }
.a11y-theme.active { border-color: var(--accent); box-shadow: 0 0 0 2px var(--accent-soft); }
.a11y-swatch { height: 14px; width: 14px; border-radius: 50%; border: 1px solid var(--border); flex: 0 0 auto; }
@media print { .a11y-fab, nav { display: none !important; } }