/* System Design Guide — shared stylesheet.
   Tokens deliberately mirror the job board's palette so the guide reads as part
   of the same site. Light is the base; dark is a token swap only. */

:root {
  color-scheme: light;
  --surface: #ffffff;
  --raised: #fbfbfe;
  --page: #f5f6fa;
  --primary: #11131b;
  --secondary: #555b6e;
  --muted: #8a90a3;
  --grid: #e6e8ef;
  --border: rgba(17, 19, 27, 0.09);
  --border-strong: rgba(17, 19, 27, 0.16);
  --series: #4f46e5;
  --accent2: #7c3aed;
  --good: #047857;
  --warning: #b45309;
  --critical: #be123c;
  --info: #0369a1;
  --goodbg: rgba(4, 120, 87, 0.09);
  --warnbg: rgba(180, 83, 9, 0.09);
  --critbg: rgba(190, 18, 60, 0.08);
  --infobg: rgba(3, 105, 161, 0.08);
  --mutedbg: rgba(17, 19, 27, 0.045);
  --accentbg: rgba(79, 70, 229, 0.08);
  --codebg: #f2f3f8;
  --shadow: 0 1px 2px rgba(17, 19, 27, 0.05), 0 8px 24px -16px rgba(17, 19, 27, 0.28);
  --shadowlift: 0 2px 6px rgba(17, 19, 27, 0.07), 0 18px 34px -20px rgba(17, 19, 27, 0.4);
  --glow: rgba(79, 70, 229, 0.13);
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --surface: #161923;
    --raised: #1c2030;
    --page: #0b0d13;
    --primary: #f3f5fa;
    --secondary: #a8aec2;
    --muted: #767d92;
    --grid: #242836;
    --border: rgba(255, 255, 255, 0.10);
    --border-strong: rgba(255, 255, 255, 0.18);
    --series: #8b8bf5;
    --accent2: #b09cf8;
    --good: #34d399;
    --warning: #fbbf24;
    --critical: #fb7185;
    --info: #38bdf8;
    --goodbg: rgba(52, 211, 153, 0.12);
    --warnbg: rgba(251, 191, 36, 0.12);
    --critbg: rgba(251, 113, 133, 0.12);
    --infobg: rgba(56, 189, 248, 0.12);
    --mutedbg: rgba(255, 255, 255, 0.055);
    --accentbg: rgba(139, 139, 245, 0.14);
    --codebg: #12151f;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.36), 0 8px 24px -16px rgba(0, 0, 0, 0.7);
    --shadowlift: 0 2px 6px rgba(0, 0, 0, 0.42), 0 18px 34px -20px rgba(0, 0, 0, 0.85);
    --glow: rgba(139, 139, 245, 0.2);
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --surface: #161923;
  --raised: #1c2030;
  --page: #0b0d13;
  --primary: #f3f5fa;
  --secondary: #a8aec2;
  --muted: #767d92;
  --grid: #242836;
  --border: rgba(255, 255, 255, 0.10);
  --border-strong: rgba(255, 255, 255, 0.18);
  --series: #8b8bf5;
  --accent2: #b09cf8;
  --good: #34d399;
  --warning: #fbbf24;
  --critical: #fb7185;
  --info: #38bdf8;
  --goodbg: rgba(52, 211, 153, 0.12);
  --warnbg: rgba(251, 191, 36, 0.12);
  --critbg: rgba(251, 113, 133, 0.12);
  --infobg: rgba(56, 189, 248, 0.12);
  --mutedbg: rgba(255, 255, 255, 0.055);
  --accentbg: rgba(139, 139, 245, 0.14);
  --codebg: #12151f;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.36), 0 8px 24px -16px rgba(0, 0, 0, 0.7);
  --shadowlift: 0 2px 6px rgba(0, 0, 0, 0.42), 0 18px 34px -20px rgba(0, 0, 0, 0.85);
  --glow: rgba(139, 139, 245, 0.2);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 84px; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: .01ms !important; animation-duration: .01ms !important; }
}

body {
  margin: 0;
  background: var(--page);
  color: var(--primary);
  font-family: var(--sans);
  font-size: 15.5px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--series); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent2); }
:where(a, button, summary, input):focus-visible {
  outline: 2px solid var(--series);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------------------------------------------------------------- top bar */

.topbar {
  position: sticky; top: 0; z-index: 40;
  background: color-mix(in srgb, var(--page) 88%, transparent);
  backdrop-filter: saturate(1.6) blur(12px);
  border-bottom: 1px solid var(--border);
}
.topbar-in {
  max-width: 1240px; margin: 0 auto; padding: 9px 20px;
  display: flex; align-items: center; gap: 14px;
}
.brand {
  display: flex; align-items: center; gap: 9px;
  font-weight: 700; font-size: 14.5px; letter-spacing: -0.015em;
  color: var(--primary); text-decoration: none; flex: none;
}
.brand .mark {
  width: 26px; height: 26px; border-radius: 8px; flex: none;
  display: grid; place-items: center; color: #fff; font-size: 13px; font-weight: 800;
  background: linear-gradient(135deg, var(--series), var(--accent2));
}
.navlinks {
  display: flex; gap: 2px; overflow-x: auto; flex: 1 1 auto;
  scrollbar-width: none; -ms-overflow-style: none;
}
.navlinks::-webkit-scrollbar { display: none; }
.navlinks a {
  padding: 6px 10px; border-radius: 8px; white-space: nowrap;
  font-size: 13.5px; font-weight: 500; color: var(--secondary); text-decoration: none;
  transition: background .15s ease, color .15s ease;
}
.navlinks a:hover { background: var(--mutedbg); color: var(--primary); }
.navlinks a[aria-current="page"] { background: var(--accentbg); color: var(--series); font-weight: 650; }
.themebtn {
  flex: none; width: 32px; height: 32px; border-radius: 9px; cursor: pointer;
  display: grid; place-items: center; font-size: 15px; line-height: 1;
  background: var(--surface); color: var(--secondary);
  border: 1px solid var(--border);
  transition: background .15s ease, color .15s ease, transform .15s ease;
}
.themebtn:hover { color: var(--primary); transform: translateY(-1px); }

/* -------------------------------------------------------------- structure */

.shell { max-width: 1240px; margin: 0 auto; padding: 0 20px 90px; }

.layout { display: grid; grid-template-columns: minmax(0, 1fr); gap: 40px; }
@media (min-width: 1060px) {
  .layout { grid-template-columns: minmax(0, 1fr) 236px; }
  .layout > .toc { order: 2; }
  .layout > main { order: 1; }
}

main { min-width: 0; max-width: 820px; }

.toc { display: none; }
@media (min-width: 1060px) {
  .toc {
    display: block; position: sticky; top: 74px; align-self: start;
    max-height: calc(100vh - 96px); overflow-y: auto; padding-bottom: 24px;
    font-size: 13.2px;
  }
  .toc h2 {
    font-size: 10.5px; text-transform: uppercase; letter-spacing: .09em;
    color: var(--muted); margin: 0 0 10px; font-weight: 700;
  }
  .toc a {
    display: block; padding: 4.5px 10px; border-radius: 6px; color: var(--secondary);
    text-decoration: none; border-left: 2px solid transparent; line-height: 1.4;
  }
  .toc a:hover { background: var(--mutedbg); color: var(--primary); }
  .toc a.active {
    color: var(--series); border-left-color: var(--series);
    background: var(--accentbg); font-weight: 600;
  }
}

/* ------------------------------------------------------------------- hero */

.hero { padding: 46px 0 30px; position: relative; }
.hero::before {
  content: ""; position: absolute; inset: -40px -40% auto; height: 420px; z-index: -1;
  background: radial-gradient(45% 55% at 50% 0%, var(--glow), transparent 72%);
  pointer-events: none;
}
.eyebrow {
  font-size: 11.5px; font-weight: 700; letter-spacing: .11em; text-transform: uppercase;
  color: var(--series); margin: 0 0 10px;
}
.hero h1 {
  font-size: clamp(30px, 5vw, 44px); line-height: 1.1; margin: 0 0 14px;
  font-weight: 780; letter-spacing: -0.032em;
  background: linear-gradient(100deg, var(--primary) 20%, var(--series) 125%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero .lede { font-size: 17px; color: var(--secondary); margin: 0; max-width: 62ch; }

/* --------------------------------------------------------------- headings */

h2.sec {
  font-size: 12px; text-transform: uppercase; letter-spacing: .1em; font-weight: 700;
  color: var(--muted); margin: 54px 0 18px; padding-bottom: 9px;
  border-bottom: 1px solid var(--border);
}
h3 { font-size: 19px; font-weight: 680; letter-spacing: -0.018em; margin: 30px 0 10px; }
h4 {
  font-size: 13px; font-weight: 700; margin: 22px 0 8px; color: var(--primary);
  letter-spacing: .005em;
}
p { margin: 0 0 14px; }
ul, ol { margin: 0 0 15px; padding-left: 21px; }
li { margin-bottom: 6px; }
li::marker { color: var(--muted); }
strong { font-weight: 650; }
hr { border: 0; border-top: 1px solid var(--border); margin: 34px 0; }

/* ------------------------------------------------------------ topic cards */

.topic {
  background: var(--surface); border: 1px solid var(--border); border-radius: 16px;
  padding: 26px 28px; margin: 24px 0; box-shadow: var(--shadow);
  scroll-margin-top: 84px;
}
@media (max-width: 600px) { .topic { padding: 20px 18px; border-radius: 13px; } }

.topic > h3:first-of-type { margin-top: 0; }
.topic-head { display: flex; align-items: flex-start; gap: 13px; margin-bottom: 6px; }
.tnum {
  flex: none; min-width: 30px; height: 30px; padding: 0 7px; border-radius: 9px;
  display: grid; place-items: center; font-size: 13px; font-weight: 750;
  font-variant-numeric: tabular-nums;
  color: #fff; background: linear-gradient(135deg, var(--series), var(--accent2));
}
.topic-head h3 { margin: 0; font-size: 21px; padding-top: 1px; }
.tags { display: flex; flex-wrap: wrap; gap: 6px; margin: 10px 0 18px; }
.tag {
  font-size: 11.5px; font-weight: 600; padding: 2.5px 9px; border-radius: 999px;
  background: var(--mutedbg); color: var(--secondary); white-space: nowrap;
}

/* ----------------------------------------------------------- call-outs */

.box {
  border-radius: 12px; padding: 15px 17px; margin: 18px 0;
  border: 1px solid var(--border); background: var(--raised);
  font-size: 14.6px;
}
.box > :last-child { margin-bottom: 0; }
.box .lbl {
  display: block; font-size: 10.5px; font-weight: 750; letter-spacing: .1em;
  text-transform: uppercase; margin-bottom: 7px;
}
.box.why { background: var(--infobg); border-color: color-mix(in srgb, var(--info) 26%, transparent); }
.box.why .lbl { color: var(--info); }
.box.say { background: var(--accentbg); border-color: color-mix(in srgb, var(--series) 28%, transparent); }
.box.say .lbl { color: var(--series); }
.box.say p { font-style: italic; }
.box.gotcha { background: var(--warnbg); border-color: color-mix(in srgb, var(--warning) 28%, transparent); }
.box.gotcha .lbl { color: var(--warning); }
.box.danger { background: var(--critbg); border-color: color-mix(in srgb, var(--critical) 28%, transparent); }
.box.danger .lbl { color: var(--critical); }
.box.win { background: var(--goodbg); border-color: color-mix(in srgb, var(--good) 28%, transparent); }
.box.win .lbl { color: var(--good); }

/* ------------------------------------------------------------------ table */

.tablewrap { overflow-x: auto; margin: 18px 0; border-radius: 12px; border: 1px solid var(--border); }
table { border-collapse: collapse; width: 100%; font-size: 14px; background: var(--surface); }
th, td { text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--border); vertical-align: top; }
thead th {
  background: var(--mutedbg); font-size: 11.5px; text-transform: uppercase;
  letter-spacing: .06em; color: var(--secondary); font-weight: 700; white-space: nowrap;
}
tbody tr:last-child td { border-bottom: 0; }
tbody tr:hover { background: var(--mutedbg); }
td code, th code { white-space: nowrap; }
.nowrap { white-space: nowrap; }

/* ------------------------------------------------------------------- code */

code {
  font-family: var(--mono); font-size: .88em; padding: 1.5px 5px; border-radius: 5px;
  background: var(--codebg); border: 1px solid var(--border); color: var(--primary);
}
pre {
  background: var(--codebg); border: 1px solid var(--border); border-radius: 12px;
  padding: 15px 17px; overflow-x: auto; margin: 16px 0;
  font-family: var(--mono); font-size: 13px; line-height: 1.6;
}
pre code { background: none; border: 0; padding: 0; font-size: inherit; }
pre .c { color: var(--muted); }
pre .k { color: var(--accent2); font-weight: 600; }
pre .s { color: var(--good); }

/* ------------------------------------------------------------ stat tiles */

.stats { display: grid; gap: 10px; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); margin: 18px 0; }
.stat {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
  padding: 13px 15px;
}
.stat .v {
  font-size: 20px; font-weight: 720; letter-spacing: -0.02em; color: var(--series);
  font-variant-numeric: tabular-nums; display: block; line-height: 1.25;
}
.stat .k { font-size: 12.2px; color: var(--secondary); display: block; margin-top: 2px; }

/* --------------------------------------------------------------- diagrams */

.diagram {
  margin: 20px 0; padding: 18px 16px; overflow-x: auto;
  background: var(--surface); border: 1px solid var(--border); border-radius: 13px;
}
.diagram svg { display: block; margin: 0 auto; max-width: 100%; height: auto; }
.diagram figcaption {
  font-size: 12.5px; color: var(--muted); text-align: center; margin-top: 12px;
  padding: 0 8px;
}
.d-fill { fill: var(--surface); }
.d-stroke { stroke: var(--border-strong); }
.d-text { fill: var(--primary); font-family: var(--sans); font-size: 12px; font-weight: 600; }
.d-sub { fill: var(--muted); font-family: var(--sans); font-size: 10.5px; font-weight: 500; }
.d-accent { fill: var(--accentbg); stroke: var(--series); }
.d-good { fill: var(--goodbg); stroke: var(--good); }
.d-warn { fill: var(--warnbg); stroke: var(--warning); }
.d-crit { fill: var(--critbg); stroke: var(--critical); }
/* Arrowheads live inside <marker>, which renders in its own context — currentColor
   there resolves against <defs>, not against the line being marked. Pinning the
   fill here keeps every arrowhead visible and on-palette in both themes. */
.diagram marker path { fill: var(--series); }
.d-line { stroke: var(--border-strong); fill: none; stroke-width: 1.5; }
.d-flow { stroke: var(--series); fill: none; stroke-width: 1.75; }
.d-dash { stroke: var(--muted); fill: none; stroke-width: 1.4; stroke-dasharray: 4 3; }

/* --------------------------------------------------------------------- QA */

details.qa {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
  margin: 10px 0; overflow: hidden;
}
details.qa[open] { box-shadow: var(--shadow); }
details.qa > summary {
  cursor: pointer; padding: 13px 17px; font-weight: 600; font-size: 15px;
  list-style: none; display: flex; gap: 11px; align-items: baseline;
  transition: background .15s ease;
}
details.qa > summary::-webkit-details-marker { display: none; }
details.qa > summary:hover { background: var(--mutedbg); }
details.qa > summary::after {
  content: "+"; margin-left: auto; color: var(--muted); font-weight: 700;
  font-size: 17px; line-height: 1; flex: none;
}
details.qa[open] > summary::after { content: "\2212"; }
details.qa > summary .qn {
  color: var(--series); font-weight: 750; font-size: 12.5px; flex: none;
  font-variant-numeric: tabular-nums; padding-top: 2px;
}
.qa-body { padding: 2px 17px 16px 45px; font-size: 14.6px; border-top: 1px solid var(--border); padding-top: 14px; }
.qa-body > :last-child { margin-bottom: 0; }
@media (max-width: 600px) { .qa-body { padding-left: 17px; } }

/* ------------------------------------------------------------- topic grid */

.grid { display: grid; gap: 12px; grid-template-columns: repeat(auto-fill, minmax(232px, 1fr)); margin: 20px 0; }
.gcard {
  display: block; text-decoration: none; color: inherit; padding: 15px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 13px;
  box-shadow: var(--shadow);
  transition: transform .16s ease, box-shadow .16s ease, border-color .16s ease;
}
@media (hover: hover) {
  .gcard:hover {
    transform: translateY(-2px); box-shadow: var(--shadowlift);
    border-color: color-mix(in srgb, var(--series) 40%, var(--border));
  }
}
.gcard .n {
  font-size: 11px; font-weight: 750; color: var(--series); letter-spacing: .06em;
  font-variant-numeric: tabular-nums;
}
.gcard .t { font-weight: 640; font-size: 15px; margin: 3px 0 4px; letter-spacing: -0.012em; }
.gcard .d { font-size: 12.8px; color: var(--secondary); line-height: 1.5; }

/* --------------------------------------------------------------- day plan */

.plan { display: grid; gap: 8px; margin: 20px 0; }
.day {
  display: flex; align-items: center; gap: 12px; padding: 11px 15px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 11px;
  transition: border-color .15s ease, opacity .15s ease;
}
.day input[type="checkbox"] {
  width: 17px; height: 17px; flex: none; cursor: pointer; accent-color: var(--series);
}
.day .dnum {
  font-size: 11px; font-weight: 700; color: var(--muted); flex: none; width: 44px;
  font-variant-numeric: tabular-nums;
}
.day label { flex: 1 1 auto; cursor: pointer; font-size: 14.5px; font-weight: 550; min-width: 0; }
.day a { font-size: 12.5px; color: var(--muted); text-decoration: none; flex: none; }
.day a:hover { color: var(--series); }
.day.done { opacity: .5; }
.day.done label { text-decoration: line-through; text-decoration-color: var(--muted); }
.progress {
  display: flex; align-items: center; gap: 12px; margin: 18px 0 6px;
  font-size: 13px; color: var(--secondary);
}
.bar { flex: 1 1 auto; height: 7px; border-radius: 99px; background: var(--mutedbg); overflow: hidden; }
.bar > i { display: block; height: 100%; width: 0; border-radius: 99px;
  background: linear-gradient(90deg, var(--series), var(--accent2)); transition: width .3s ease; }

/* ------------------------------------------------------------- prev/next */

.pager { display: grid; gap: 12px; grid-template-columns: 1fr 1fr; margin: 56px 0 0; }
@media (max-width: 560px) { .pager { grid-template-columns: 1fr; } }
.pager a {
  display: block; padding: 15px 17px; border-radius: 13px; text-decoration: none;
  background: var(--surface); border: 1px solid var(--border); color: inherit;
  box-shadow: var(--shadow); transition: transform .16s ease, border-color .16s ease;
}
.pager a:hover { transform: translateY(-2px); border-color: color-mix(in srgb, var(--series) 40%, var(--border)); }
.pager .dir { font-size: 11px; font-weight: 700; letter-spacing: .09em; text-transform: uppercase; color: var(--muted); }
.pager .ttl { font-weight: 640; font-size: 15px; margin-top: 3px; letter-spacing: -0.012em; }
.pager .next { text-align: right; }

/* ------------------------------------------------------------------- misc */

.callout-row { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.footer {
  margin-top: 70px; padding-top: 22px; border-top: 1px solid var(--border);
  font-size: 13px; color: var(--muted);
}
.footer a { color: var(--secondary); }
.pillrow { display: flex; flex-wrap: wrap; gap: 8px; margin: 16px 0 24px; }
.pill {
  padding: 6px 13px; border-radius: 999px; font-size: 13px; font-weight: 600;
  text-decoration: none; background: var(--surface); color: var(--secondary);
  border: 1px solid var(--border); transition: all .15s ease;
}
.pill:hover { border-color: var(--series); color: var(--series); }
.pill.solid { background: linear-gradient(135deg, var(--series), var(--accent2)); color: #fff; border-color: transparent; }
.pill.solid:hover { color: #fff; opacity: .9; }
.lead-in { font-size: 16.2px; color: var(--secondary); margin-bottom: 22px; max-width: 66ch; }
.tiny { font-size: 12.5px; color: var(--muted); }

.split { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); margin: 18px 0; }
.split .box { margin: 0; height: 100%; }

/* ------------------------------------------------------------------ print */

@media print {
  .topbar, .toc, .pager, .themebtn, .footer { display: none !important; }
  body { background: #fff; color: #000; font-size: 10.5pt; }
  .shell { max-width: none; padding: 0; }
  main { max-width: none; }
  .topic, .box, .stat, .diagram, .tablewrap, details.qa {
    break-inside: avoid; box-shadow: none; border-color: #ccc;
  }
  details.qa[open] > summary::after, details.qa > summary::after { content: ""; }
  details.qa > .qa-body { display: block !important; }
  a { color: #000; text-decoration: none; }
  h2.sec { break-after: avoid; }
}