/* ============================================================================
   System Design Studio — skeleton stylesheet (the only place styling lives).
   Content fragments carry semantics only; everything visual is here.
   Minimal "engineering review journal": grotesk display + serif reading body +
   monospace metadata, near-monochrome with one restrained accent, light/dark.
   ========================================================================== */

:root {
  --bg:        #f7f7f6;
  --surface:   #ffffff;
  --surface-2: #f1f2f4;
  --text:      #16181d;
  --muted:     #5b6573;   /* secondary text only — never key values */
  --faint:     #8a93a1;   /* tertiary: footers, hairline labels */
  --border:    #e4e6ea;
  --border-2:  #d6d9df;
  --accent:    #4f46e5;
  --accent-ink:#ffffff;
  --accent-weak:#ecebfd;
  --shadow:    0 1px 2px rgba(16,21,28,.05), 0 10px 30px rgba(16,21,28,.06);
  --maxw:      1080px;
  --readw:     46rem;
}
html[data-theme="dark"] {
  --bg:        #0c0e14;
  --surface:   #13161f;
  --surface-2: #181c28;
  --text:      #e9ebf0;
  --muted:     #9aa3b2;
  --faint:     #6c7585;
  --border:    #222634;
  --border-2:  #2c3242;
  --accent:    #8b93ff;
  --accent-ink:#0c0e14;
  --accent-weak:#191d2e;
  --shadow:    0 1px 2px rgba(0,0,0,.4), 0 14px 36px rgba(0,0,0,.5);
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Source Serif 4", Georgia, "Times New Roman", serif;
  font-size: 17px;
  line-height: 1.72;
  font-optical-sizing: auto;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
.display { font-family: "Space Grotesk", system-ui, sans-serif; }
.mono, time, .tag, .fam, .kbd, code, kbd, .meta-row, .eyebrow {
  font-family: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
img, svg { max-width: 100%; }

/* ---- layout ---------------------------------------------------------------- */
.container { max-width: var(--maxw); margin: 0 auto; padding: 0 clamp(18px, 4vw, 40px); }
.reading   { max-width: var(--readw); margin: 0 auto; }
main { padding: clamp(28px, 5vw, 56px) 0 64px; }

/* ---- top bar --------------------------------------------------------------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: saturate(1.2) blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-header .bar { display: flex; align-items: center; justify-content: space-between; height: 60px; gap: 18px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: -.01em; color: var(--text); font-size: 16px; }
.brand:hover { text-decoration: none; }
.brand svg { width: 22px; height: 22px; }
.nav { display: flex; align-items: center; gap: 6px; }
.nav a { color: var(--muted); font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 13px; padding: 7px 11px; border-radius: 8px; }
.nav a:hover { color: var(--text); text-decoration: none; background: var(--surface-2); }
.nav a.active { color: var(--text); background: var(--surface-2); }
.theme-toggle {
  cursor: pointer; border: 1px solid var(--border); background: var(--surface); color: var(--text);
  width: 34px; height: 34px; border-radius: 9px; display: grid; place-items: center; font-size: 15px;
}
.theme-toggle:hover { border-color: var(--border-2); }

/* ---- masthead (landing) ---------------------------------------------------- */
.masthead { padding-top: 8px; }
.masthead h1 { font-size: clamp(30px, 6vw, 50px); font-weight: 700; letter-spacing: -.025em; line-height: 1.04; margin: 0; }
.masthead .lede { color: var(--muted); max-width: 52ch; margin: .7rem 0 0; font-size: 18px; }

/* ---- coverage strip (signature) ------------------------------------------- */
.coverage { margin: 32px 0 10px; }
.eyebrow { font-size: 11px; letter-spacing: .14em; text-transform: uppercase; color: var(--faint); margin: 0 0 12px; }
.fams { display: flex; flex-wrap: wrap; gap: 8px; }
.fam { font-size: 12.5px; padding: 4px 10px; border-radius: 8px; border: 1px solid var(--border); white-space: nowrap; }
.fam.on  { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.fam.off { background: transparent; color: var(--faint); }

/* ---- filter + grid + cards ------------------------------------------------- */
.filter { margin: 28px 0 18px; }
.filter input {
  width: 100%; padding: 13px 16px; border-radius: 12px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font-size: 15px; font-family: inherit;
}
.filter input:focus { border-color: var(--accent); }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 16px; }
.card {
  display: flex; flex-direction: column; color: inherit; background: var(--surface);
  border: 1px solid var(--border); border-radius: 16px; padding: 22px; box-shadow: var(--shadow);
  transition: transform .15s ease, border-color .15s ease;
}
.card:hover { transform: translateY(-3px); border-color: var(--accent); text-decoration: none; }
.card .row { display: flex; justify-content: space-between; align-items: center; color: var(--muted); font-size: 12.5px; }
.card .diff { padding: 2px 9px; border: 1px solid var(--border); border-radius: 7px; text-transform: capitalize; }
.card h2 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 20px; line-height: 1.22; letter-spacing: -.012em; margin: 13px 0 8px; }
.card p { margin: 0 0 16px; font-size: 15px; color: var(--text); }
.card .tags { margin-top: auto; display: flex; flex-wrap: wrap; gap: 6px; }
.tag { font-size: 11.5px; padding: 3px 8px; border-radius: 7px; background: var(--surface-2); color: var(--muted); }
.empty { grid-column: 1/-1; text-align: center; padding: 72px 20px; border: 1px dashed var(--border); border-radius: 16px; color: var(--muted); }
.empty h2 { font-family: "Space Grotesk", system-ui, sans-serif; color: var(--text); margin: 0 0 8px; }
.nohits { grid-column: 1/-1; color: var(--muted); padding: 20px 4px; }

/* ---- design header + subnav ----------------------------------------------- */
.doc-head { border-bottom: 1px solid var(--border); padding-bottom: 22px; margin-bottom: 8px; }
.doc-head h1 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: clamp(26px, 4.4vw, 40px); font-weight: 700; letter-spacing: -.02em; line-height: 1.08; margin: 6px 0 0; }
.doc-head .summary { color: var(--muted); font-size: 18px; margin: 10px 0 16px; max-width: 60ch; }
.meta-row { display: flex; flex-wrap: wrap; gap: 14px; font-size: 12.5px; color: var(--faint); }
.meta-row .tags { display: inline-flex; gap: 6px; flex-wrap: wrap; }
.subnav { display: inline-flex; background: var(--surface-2); border: 1px solid var(--border); border-radius: 11px; padding: 4px; gap: 4px; margin: 20px 0 0; }
.subnav a { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 13px; color: var(--muted); padding: 7px 14px; border-radius: 8px; }
.subnav a:hover { color: var(--text); text-decoration: none; }
.subnav a.active { color: var(--text); background: var(--surface); box-shadow: var(--shadow); }

/* ---- transcript / reading prose ------------------------------------------- */
.prose { margin-top: 30px; }
.prose h2 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 23px; letter-spacing: -.015em; margin: 44px 0 14px; line-height: 1.2; }
.prose h2.beat::before { content: attr(data-beat); display: inline-block; font-family: ui-monospace, Menlo, monospace; font-size: 13px; color: var(--accent); margin-right: 12px; vertical-align: 2px; }
.prose h3 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 18px; margin: 28px 0 10px; }
.prose p { margin: 0 0 18px; }
.prose ul, .prose ol { margin: 0 0 18px; padding-left: 1.3em; }
.prose li { margin: 6px 0; }
.prose strong { font-weight: 600; }
.prose code { background: var(--surface-2); padding: .12em .4em; border-radius: 5px; font-size: .88em; }
.prose pre { background: var(--surface-2); border: 1px solid var(--border); border-radius: 12px; padding: 16px 18px; overflow: auto; margin: 0 0 20px; }
.prose pre code { background: none; padding: 0; font-size: 13.5px; line-height: 1.6; }

/* dialogue: the signature reading device */
.turn { display: grid; grid-template-columns: 4.5rem 1fr; gap: 16px; margin: 0 0 18px; align-items: start; }
.turn .who { font-family: ui-monospace, Menlo, monospace; font-size: 11px; letter-spacing: .08em; text-transform: uppercase; color: var(--faint); padding-top: .35rem; }
.turn .say { }
.turn .say > :last-child { margin-bottom: 0; }
.turn.principal { background: var(--accent-weak); border-left: 2px solid var(--accent); border-radius: 0 12px 12px 0; padding: 14px 18px 14px 16px; }
.turn.principal .who { color: var(--accent); }
.turn.staff { padding: 2px 0 2px 16px; }

/* callouts */
aside { margin: 0 0 20px; padding: 14px 18px; border-radius: 12px; border: 1px solid var(--border); font-size: 16px; }
aside .label { display: block; font-family: ui-monospace, Menlo, monospace; font-size: 10.5px; letter-spacing: .12em; text-transform: uppercase; margin-bottom: 6px; color: var(--faint); }
aside.decision { background: var(--surface); border-left: 3px solid var(--accent); }
aside.decision .label { color: var(--accent); }
aside.tradeoff { background: var(--surface-2); }
aside.note     { background: var(--surface); }
.napkin { background: var(--surface-2); border: 1px solid var(--border); border-radius: 12px; padding: 16px 20px; margin: 0 0 22px; }
.napkin .label { display:block; font-family: ui-monospace, Menlo, monospace; font-size: 10.5px; letter-spacing:.12em; text-transform: uppercase; color: var(--faint); margin-bottom: 8px; }

.prevnext { display: flex; justify-content: space-between; gap: 12px; margin-top: 56px; padding-top: 20px; border-top: 1px solid var(--border); font-size: 14px; }
.prevnext a { color: var(--muted); } .prevnext a:hover { color: var(--text); }

/* ---- scrollytelling architecture ------------------------------------------ */
.scrolly-intro { color: var(--muted); font-size: 18px; max-width: 60ch; margin: 26px 0 8px; }
.scrolly { display: grid; grid-template-columns: 1fr 38%; gap: clamp(24px, 4vw, 56px); align-items: start; margin-top: 24px; }
.scrolly-steps { }
.step { min-height: 78vh; display: flex; flex-direction: column; justify-content: center; padding: 4vh 0; opacity: .42; transition: opacity .35s ease; }
.step.active { opacity: 1; }
.step .num { font-family: ui-monospace, Menlo, monospace; font-size: 12px; letter-spacing: .12em; color: var(--accent); }
.step h3 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 22px; letter-spacing: -.015em; margin: 6px 0 10px; }
.step p { margin: 0; font-size: 17px; }
.scrolly-graphic { position: sticky; top: 88px; height: min(74vh, 620px); border: 1px solid var(--border); border-radius: 16px; background: var(--surface); box-shadow: var(--shadow); display: grid; place-items: center; padding: 18px; overflow: hidden; }
.scrolly-graphic svg { width: 100%; height: 100%; color: var(--text); }
.scrolly-progress { position: absolute; left: 0; top: 0; height: 3px; width: 0; background: var(--accent); transition: width .25s ease; }

/* layered diagram reveal */
[data-reveal] { opacity: 0; transform: translateY(6px) scale(.99); transition: opacity .5s ease, transform .5s ease; }
[data-reveal].reveal-on { opacity: 1; transform: none; }
[data-reveal].reveal-current { }
.node rect, .node circle, .node path.box { fill: var(--surface-2); stroke: var(--border-2); stroke-width: 1.5; }
.node text { fill: var(--text); font-family: ui-monospace, Menlo, monospace; font-size: 13px; }
.node .sub { fill: var(--muted); font-size: 11px; }
.edge { fill: none; stroke: var(--muted); stroke-width: 1.6; }
.edge.flow { stroke-dasharray: 5 5; }
.reveal-current .node rect, .reveal-current .node circle { stroke: var(--accent); stroke-width: 2.2; }
.reveal-current .edge { stroke: var(--accent); }
.lane-label { fill: var(--faint); font-family: ui-monospace, Menlo, monospace; font-size: 10.5px; letter-spacing: .1em; }

/* ---- patterns (per-design + aggregate) ------------------------------------ */
.pattern-grid { display: grid; grid-template-columns: 1fr; gap: 16px; margin-top: 28px; }
.pattern { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; padding: 20px 22px; box-shadow: var(--shadow); }
.pattern .family-tag { font-family: ui-monospace, Menlo, monospace; font-size: 11.5px; color: var(--accent); }
.pattern h3 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 18px; letter-spacing: -.01em; margin: 8px 0 12px; }
.pattern dl { margin: 0; display: grid; grid-template-columns: 5.2rem 1fr; gap: 6px 12px; font-size: 14.5px; }
.pattern dt { font-family: ui-monospace, Menlo, monospace; font-size: 11px; letter-spacing: .06em; text-transform: uppercase; color: var(--faint); padding-top: 3px; }
.pattern dd { margin: 0; }
.pattern .src { margin-top: 14px; font-size: 12.5px; }
.family-group { margin: 40px 0 0; }
.family-group > h2 { font-family: "Space Grotesk", system-ui, sans-serif; font-size: 15px; letter-spacing: .02em; text-transform: capitalize; color: var(--text); border-bottom: 1px solid var(--border); padding-bottom: 8px; }

/* ---- footer ---------------------------------------------------------------- */
.site-footer { border-top: 1px solid var(--border); margin-top: 56px; }
.site-footer .bar { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px; padding: 22px 0; color: var(--faint); font-family: ui-monospace, Menlo, monospace; font-size: 12.5px; }

/* ---- responsive ------------------------------------------------------------ */
@media (max-width: 860px) {
  .scrolly { grid-template-columns: 1fr; }
  .scrolly-graphic { position: sticky; top: 64px; order: -1; height: 46vh; margin-bottom: 8px; }
  .step { min-height: 0; padding: 16px 0; }
}
@media (prefers-reduced-motion: reduce) {
  .card, .step, [data-reveal], .scrolly-progress { transition: none; }
  [data-reveal] { opacity: 1; transform: none; }
  .step { opacity: 1; }
}