/* ──────────────────────────────────────────────────────────────────────
 * controlsfreak.dev — shared design system
 *
 * Every page links this file (<link rel="stylesheet" href="/styles.css">).
 * It holds the whole vocabulary: the :root custom properties (the theme —
 * change colors here, not in pages) and the component classes (.tool-card,
 * .tabs, .form-row, .result-panel, .site-nav, …). Pages should be built
 * from these, not freshly styled.
 *
 * Page-specific CSS still lives inline on the page that needs it
 * (e.g. contact.html's honeypot/intro rules) — only genuinely shared rules
 * belong here. The 11ty build templates the HTML chrome and passthrough-
 * copies this file unchanged; the browser loads it directly, no bundler or
 * preprocessor in the pipeline.
 * ────────────────────────────────────────────────────────────────────── */

:root {
    color-scheme: light;
    --bg:           #eef1ec;   /* app chrome — light warm gray-green */
    --surface:      #ffffff;   /* content panes */
    --surface-2:    #f2f6f1;   /* panel headers, table heads, insets */
    --surface-3:    #e8ece4;   /* recessed background for reference / context panels — a notch below --bg */
    --border:       #ccd7c8;   /* hairlines — panel & section edges */
    --border-faint: #e3e8df;   /* lighter hairline for inner row dividers (property-sheet rows, dense tables) */
    --accent:       #43881c;   /* the green — readable on white for text & UI */
    --accent-dim:   rgba(67,136,28,0.10);
    --accent-glow:  rgba(67,136,28,0.22);
    --accent-soft:  rgba(67,136,28,0.06);  /* one notch under --accent-dim — backdrops for status pills, inset washes; never compete with --accent-glow on focus rings */
    --text:         #38423a;   /* body copy */
    --text-bright:  #1d251f;   /* headings */
    --text-dim:     #666e66;   /* labels, secondary text */
    --blue:         #1577b8;   /* data readouts / highlight — workstation blue; also "supply water" in the hydronic diagrams */
    --blue-cool:    #5e8aa0;   /* a muted, cooler companion to --blue — "return water" in the hydronic diagrams (paired with a dashed line so it reads without colour too) */
    --red:          #c4382f;   /* fault / alarm */
    --heat:         #c8782a;   /* warm orange — "heating" on the psychrometric chart's process lines; companion to --blue for cooling */
    --teal:         #4a8a8a;   /* desaturated teal — data/comm traces on the background schematic (BACnet, IP) */
    --teal-dim:     rgba(74,138,138,0.10);
    --teal-glow:    rgba(74,138,138,0.22);
    --amber:        #c9a14a;   /* desaturated amber — energized control wiring on the background schematic; section accent for /practice/ */
    --amber-dim:    rgba(201,161,74,0.10);
    --amber-glow:   rgba(201,161,74,0.22);
    --plum:         #8a5e7e;   /* desaturated plum — logic-signal lines on the background schematic */
    --plum-dim:     rgba(138,94,126,0.10);
    --plum-glow:    rgba(138,94,126,0.22);
    --mono:         'IBM Plex Mono', monospace;
    --sans:         'Overpass', sans-serif;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
    background-color: var(--bg);
    /* v2.0.1 — blueprint grid behind everything. 1.5px hairlines in
       --border every 40px. Sits only in the regions of body that
       AREN'T covered by an opaque content panel — nav (--surface),
       hero (--surface), tool-cards (--surface), footer (--surface-2)
       all paint over it, so the grid only reads in the gutters around
       and below the content. Hidden on print via the @media print
       block below.
       Weight tuned on feedback after the first pass: 1px in
       --border-faint was too quiet to read as drafting paper; 3-4px
       crosses into graph-paper foreground. 1.5px in --border is the
       balance — confident in the gutters, never patterning against
       the panels. */
    background-image:
        linear-gradient(to right,  var(--border) 1.5px, transparent 1.5px),
        linear-gradient(to bottom, var(--border) 1.5px, transparent 1.5px);
    background-size: 40px 40px;
    color: var(--text);
    font-family: var(--sans);
    font-size: 18px;
    line-height: 1.6;
    min-height: 100vh;
    /* sticky footer: stack nav / (hero?) / main / footer in a flex column
       and let main grow, so the footer hugs the viewport bottom on short pages
       instead of leaving a big gap underneath. */
    display: flex;
    flex-direction: column;
    /* Stacking context for the gutter schematic SVGs (.schematic-bg),
       which sit at z-index:-1 — above body's bg-image grid but below
       every content surface (nav, hero, main, footer). Without
       isolation:isolate the SVGs would fall behind body's background
       and disappear entirely. */
    position: relative;
    isolation: isolate;
}
main { flex: 1; }

/* Hide the blueprint grid on print — a printable page wants a clean
   white background, not drafting paper. (Same posture browsers take
   for background-image: most won't print it by default anyway, but
   the explicit rule keeps the behavior unambiguous and disables it
   under any future print-CSS overrides too.) */
@media print {
    body { background-image: none; }
}

/* ──────────────────────────────────────────────────────────────────
 * SCHEMATIC BACKGROUND — gutter as-builts
 *
 * Two narrow vertical strips, one in each side gutter, holding
 * inline-SVG schematic motifs (piping, control wiring, function
 * blocks). Each motif draws itself in via stroke-dashoffset as it
 * scrolls into view — see /scripts/schematic-bg.js for the
 * IntersectionObserver that toggles .is-drawn.
 *
 * The strips paint at z-index:-1 inside body's stacking context, so
 * they sit above body's grid background but below every content
 * surface (nav, hero, tool-cards, footer). Width tracks the gutter
 * via clamp() so the strips stay narrow on narrow viewports and
 * never push into the 1120px content column. Below 1240px the
 * gutter gets too cramped to read — strips drop out entirely there.
 *
 * Hidden in print (matches the grid). Reduced-motion: the global
 * block at the bottom of this file collapses transition-duration
 * to 0.01ms, and schematic-bg.js draws every motif synchronously
 * on load instead of observing — so reduced-motion users see the
 * end state with no reveal. */
.schematic-bg {
    position: absolute;
    top: 0;
    bottom: 0;
    z-index: -1;
    pointer-events: none;
    /* Fill (almost) all of the gutter on wide displays so motifs scale
       up via the SVG's width:100% and read across the strip, not just
       the outer half. Capped at 340px so ultra-wide displays don't
       balloon them into competing with content. */
    width: min(340px, calc((100vw - 1180px) / 2));
    overflow: hidden;
}
.schematic-bg--left  { left: 8px; }
.schematic-bg--right { right: 8px; }

.sbg-motif {
    position: absolute;
    left: 0;
    top: var(--sbg-y, 0);
    width: 100%;
    height: auto;
    opacity: 0;
    transition: opacity 700ms ease;
}
/* `fill: none` on stroked paths is set as an inline presentation
   attribute in the partial — left over from when motifs used <use>
   shadow trees; kept inline because it costs nothing.

   Draw-in via a generous fixed dasharray. The largest motif path
   here is ~200 user units (the BACnet chip's perimeter); 600 puts
   us comfortably above that with margin to spare, so dashoffset:600
   parks every path fully invisible and the transition to 0 sweeps
   the whole path on for every motif. Three earlier approaches all
   failed:

     - `getTotalLength()`-derived `--sbg-len` CSS variable — hit
       Chromium quirks on Bezier paths and circles; they refused to
       draw fully even with offset=0.
     - `pathLength="1"` normalization on every stroke — same Chromium
       quirk on Bezier paths and circles.
     - `pathLength="1"` normalization opt-in only on safe straight
       elements (lines and L-only paths), with the bulk-fallback
       still fixed-600 — this DID render those elements correctly
       in the path-length sense, but Chromium does not honor
       pathLength="1" for `stroke-dasharray` computation: a value of
       `1` is treated as 1 actual pixel, not as 1 unit of the
       normalized path. Result: a 104px line ends up with 52
       alternating 1px dashes/gaps and renders as a near-invisible
       speckle. Verified with `getTotalLength()` returning the
       geometric length (104) while `stroke-dasharray` resolves to
       `1px` (commit b8dae2b shipped this and was reverted in the
       next commit).

   A fixed dasharray well above any path length sidesteps all three
   bugs. Trade-off accepted: drawing is no longer proportional to
   path length — short signal wires finish in ~10% of the transition
   and then sit still while long pipe runs continue drawing. The
   ease-out timing softens the disparity, and correctness beats
   uniformity here. See codebase-issues#69 for the full history and
   the revisit trigger. */
.sbg-motif [data-sbg-stroke] {
    stroke-width: 1.4;
    vector-effect: non-scaling-stroke;
    stroke-dasharray: 600;
    stroke-dashoffset: 600;
}
.sbg-motif.is-drawn { opacity: 1; }
.sbg-motif.is-drawn [data-sbg-stroke] {
    stroke-dashoffset: 0;
    transition: stroke-dashoffset 3000ms ease-out;
}

.sbg-label {
    font-family: var(--mono);
    font-size: 9px;
    fill: var(--text-dim);
    letter-spacing: 0.04em;
}

@media (max-width: 1240px) {
    .schematic-bg { display: none; }
}
@media print {
    .schematic-bg { display: none; }
}

/* ── Skip-to-content link — keyboard users tab here first on every
       page and can Enter to jump past the nav. Positioned off-screen
       via negative top so it stays in the DOM (tabbable) but doesn't
       show; slides into view when focused. Same idiom as the well-
       known WebAIM pattern. */
.skip-link {
    position: absolute;
    top: -100px;
    left: 0.5rem;
    z-index: 200;
    padding: 0.6rem 1rem;
    background: var(--accent);
    color: var(--surface);
    font-family: var(--mono);
    font-size: 0.85rem;
    text-decoration: none;
    border-radius: 0 0 3px 3px;
    transition: top 0.15s;
}
.skip-link:focus { top: 0; outline: 2px solid var(--accent-glow); outline-offset: 2px; }

/* ── SITE NAV (every page carries the same nav markup) ── */
.site-nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 0.9rem 2rem;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 0.4rem 1.75rem;
}
.site-nav-brand {
    font-family: var(--mono);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    letter-spacing: 0.01em;
    text-decoration: none;
}
.site-nav-brand span {
    color: var(--accent);
    animation: breathe 4s ease-in-out infinite;
}
.site-nav-brand:hover { color: var(--text-bright); }
.site-nav-links { display: flex; flex-wrap: wrap; gap: 1.75rem; }
.site-nav-links a {
    font-family: var(--sans);
    font-size: 0.95rem;
    color: var(--text-dim);
    text-decoration: none;
    padding-bottom: 0.15rem;
    border-bottom: 2px solid transparent;
    transition: color 0.18s, border-color 0.18s;
}
.site-nav-links a:hover { color: var(--text); border-bottom-color: var(--accent); }
.site-nav-links a.active { color: var(--text-bright); border-bottom-color: var(--accent); }

/* ── UNITS TOGGLE ────────────────────────────────────────────────────
   Sits inside .site-nav-links (rightmost child) so the existing nav
   flex layout doesn't need rework. "Units:" label in mono dim text,
   followed by a two-segment pill. Active button is filled with the
   accent-dim tint via [data-units] on <html> — a tiny inline head
   script sets that attribute before first paint to avoid flashing
   the wrong button to returning metric users. The button's `.active`
   class is a backstop; the [data-units] selector is the canonical
   driver. */
.units-toggle {
    display: inline-flex;
    align-items: center;
    gap: 0.55rem;
}
.units-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}
.units-toggle-pill {
    display: inline-flex;
    border: 1px solid var(--border);
    border-radius: 2px;
    overflow: hidden;
    background: var(--surface);
}
.units-btn {
    font-family: var(--mono);
    font-size: 0.7rem;
    padding: 0.22rem 0.6rem;
    background: transparent;
    color: var(--text-dim);
    border: none;
    cursor: pointer;
    letter-spacing: 0.03em;
    transition: color 0.18s, background 0.18s;
}
.units-btn + .units-btn { border-left: 1px solid var(--border); }
.units-btn:hover { color: var(--text); }
html[data-units="us"]     .units-btn[data-units="us"],
html[data-units="metric"] .units-btn[data-units="metric"] {
    background: var(--accent-dim);
    color: var(--accent);
    font-weight: 600;
}

/* ── HERO — "workstation panel" treatment (v2.0.0).
       The hero is now a bordered surface with a faux BAS title bar above
       and a live status line below. Existing eyebrow / h1 / p / badges
       move INSIDE a .hero-body wrapper that carries the old padding. The
       outer .hero supplies the chrome; .hero-body supplies the content.
       Sub-pages don't carry a .hero, so this only affects the home page. */
.hero {
    position: relative;
    z-index: 1;
    padding: 0;
    max-width: 1120px;
    margin: 2.5rem auto 2rem;
    width: 100%;   /* don't shrink-to-fit inside body's flex column */
    text-align: left;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    overflow: hidden;
    animation: fadeUp 0.5s ease both;
}
.hero-body {
    padding: 5rem 2rem 4rem;
    text-align: center;
}
.console-titlebar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.55rem 1rem;
    border-bottom: 1px solid var(--border);
    background: var(--surface-2);
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}
.console-titlebar .titlebar-dots {
    color: var(--text-dim);
    margin: 0 0.4rem;
}
/* Three-column grid (1fr · auto · 1fr) so the middle item lands at the
   true visual center of the card — flex + space-between distributes by
   midpoint between the outer items' inside edges, which drifts off
   true-center when the OK pill and LAST BUILT have different widths
   (and shifts the version label off the hero h1's center axis above).
   The outer 1fr cells get equal width; the middle auto cell sizes to
   content and centers itself between them. */
.console-statusline {
    padding: 0.7rem 1rem;
    border-top: 1px solid var(--border);
    background: var(--surface-2);
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    gap: 0.5rem 1.25rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    font-variant-numeric: tabular-nums;
}
.console-statusline > :first-child  { justify-self: start; }
.console-statusline > :nth-child(2) { justify-self: center; }
.console-statusline > :last-child   { justify-self: end; }
.console-statusline > span strong {
    color: var(--text);
    font-weight: 600;
    margin-left: 0.35rem;
}

/* The .ok-pill: a small accent pill with a leading dot. Used in the
   title bar, status line, footer, and anywhere a "live / running"
   marker is wanted. */
.ok-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    background: var(--accent-dim);
    color: var(--accent);
    border: 1px solid var(--accent-glow);
    padding: 0.1rem 0.5rem;
    border-radius: 2px;
    font-family: var(--mono);
    font-size: 0.62rem;
    letter-spacing: 0.07em;
    text-transform: uppercase;
    font-weight: 600;
}
.ok-pill::before {
    content: "";
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent);
}

/* Centered eyebrow: short accent line on each side of the label so the
   visual weight balances. ::before stays for the original left line;
   ::after mirrors it on the right. */
.hero-eyebrow {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.16em;
    margin-bottom: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.6rem;
}
.hero-eyebrow::before,
.hero-eyebrow::after {
    content: '';
    display: block;
    width: 22px;
    height: 1px;
    background: var(--accent);
}

.hero h1 {
    font-family: var(--mono);
    font-size: clamp(1.8rem, 4.5vw, 3rem);
    font-weight: 600;
    color: var(--text-bright);
    line-height: 1.18;
    margin-bottom: 1.1rem;
    letter-spacing: -0.02em;
}
.hero h1 em { font-style: normal; color: var(--accent); }

.hero p {
    font-size: 1.05rem;
    font-weight: 300;
    color: var(--text);
    max-width: 540px;
    margin: 0 auto 2rem;   /* auto x-margins center the constrained paragraph */
    line-height: 1.8;
}

/* Beginner onramp — a single line above the badges pointing newcomers at
   the Education lane, since the badges/Browse stage presume you already
   know which tool you need. Element-qualified (p.hero-onramp) so it ties
   `.hero p` on specificity and wins the cascade, overriding the centered
   subhead paragraph styling. */
p.hero-onramp {
    font-size: 0.9rem;
    font-weight: 400;
    color: var(--text-dim);
    max-width: none;
    margin: 0 auto 1.4rem;
    line-height: 1.6;
}
p.hero-onramp a { color: var(--accent); white-space: nowrap; border-bottom: 1px solid transparent; }
p.hero-onramp a:hover { border-bottom-color: var(--accent); }

.hero-badges { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.5rem; }
.badge {
    font-family: var(--mono);
    font-size: 0.68rem;
    padding: 0.28rem 0.7rem;
    border: 1px solid var(--border);
    border-radius: 2px;
    color: var(--text-dim);
    background: var(--surface);
    letter-spacing: 0.05em;
}

/* ── MAIN ── */
/* The home page puts a .hero between the nav and main, so main doesn't need
   its own top padding there — .hero already provides air. Sub-pages have no
   hero, so main supplies the breathing room itself. The adjacent-sibling
   selector below zeroes out the top padding when a hero comes first. */
main {
    position: relative;
    z-index: 1;
    max-width: 1120px;
    margin: 0 auto;
    padding: 2.5rem 2rem 4rem;
    width: 100%;
}
.hero + main { padding-top: 0; }

.section-header {
    display: flex;
    align-items: baseline;
    gap: 0.6rem;
    margin-bottom: 1.5rem;
}
.section-label {
    font-family: var(--mono);
    font-size: 0.82rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    white-space: nowrap;
    margin: 0;
}
/* The trailing hairline that used to follow every section-label is
   hidden in v2.0.0 — the SEC:NNN section-number prefix on h2 labels
   carries enough left-side weight that a trailing line is noise. The
   markup stays in existing pages as a no-op so a future tweak can flip
   it back without retroactive edits; new pages can omit it. */
.section-line { display: none; }

/* h2.section-label is the section-divider variant (vs h1.section-label
   which is a landing-page title). One BAS-instrument prefix mode:

   - `data-stage="N"` renders `STAGE:N · LABEL`. Evokes equipment
     staging (Stage 1 / Stage 2 cooling, lead/lag pumps) — used on
     the home page where the sections read as a staged sequence:
     Stage 1 first, then Stage 2 if you want more, then Stage 3 for
     backstory.

   The accent color attaches to the prefix, not the label — the prefix
   becomes the wayfinding mark, the label reads as a quiet workstation
   heading. Pages without the attribute are unaffected (no prefix;
   existing accent label color preserved). */
h2.section-label[data-stage] {
    font-size: 0.78rem;
    letter-spacing: 0.06em;
    color: var(--text-bright);
}
h2.section-label[data-stage]::before {
    color: var(--accent);
    font-variant-numeric: tabular-nums;
    margin-right: 0.1rem;
    font-weight: 600;
    content: "STAGE:" attr(data-stage) " · ";
}

/* ── TOOL CARD ── */
.tool-card {
    position: relative;            /* anchor for the .tool-card-fullscreen-btn */
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 1.5rem;
}
/* :nth-of-type counts tool-card siblings independently of a leading
   .section-header div; nth-child counts all siblings and would shift
   indices by one on every content page. Four indices covers the longest
   tool-card stack today (4 on pid-basics: page topic + 3 mini-sims). */
.tool-card:nth-of-type(1) { animation: fadeUp 0.5s 0.08s ease both; }
.tool-card:nth-of-type(2) { animation: fadeUp 0.5s 0.16s ease both; }
.tool-card:nth-of-type(3) { animation: fadeUp 0.5s 0.24s ease both; }
.tool-card:nth-of-type(4) { animation: fadeUp 0.5s 0.32s ease both; }

.tool-card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.9rem 1.5rem;
    border-bottom: 1px solid var(--border);
    background: var(--surface-2);
}
.tool-card-title {
    font-family: var(--mono);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-bright);
    display: flex;
    align-items: center;
    gap: 0.7rem;
    margin: 0;
}
.tool-tag {
    font-family: var(--mono);
    font-size: 0.62rem;
    padding: 0.15rem 0.5rem;
    background: var(--accent-dim);
    color: var(--accent);
    border: 1px solid var(--accent-glow);
    border-radius: 2px;
    text-transform: uppercase;
    letter-spacing: 0.07em;
}
.tool-body { padding: 1.5rem; }
.tool-body p { font-size: 0.95rem; line-height: 1.8; color: var(--text); }
.tool-body a { color: var(--accent); }
/* Body-prose lists — same font triplet as .tool-body p. Per-list margin
   stays inline (it varies). A page that wants a tighter small-text list
   overrides font-size/line-height inline; the inline style wins. */
.tool-body ul { font-size: 0.95rem; line-height: 1.8; color: var(--text); }

/* Mono small-caps preamble caption that sits under a .tool-card-header.
   Element-qualified to tie .tool-body p's (0,0,1,1) specificity and win
   on cascade order, matching p.bit-hint / p.pid-note / p.ref-note.
   Padding/margin stays per-site inline — value varies by whether the
   preamble sits outside .tool-body (between header and the next block)
   or inside .tool-body (where .tool-body's own padding applies). */
p.tool-preamble {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    line-height: 1.7;
}

/* Lead paragraph on Education pages — the opening prose paragraph that
   sets up the lesson. Slightly larger / wider line-height than the body
   .tool-body p shape. Spans the full .tool-body width so the intro
   doesn't read as marooned in the left half of the card. Placed before
   .callout p (cascade order) so .callout p's tighter font shape stays
   authoritative inside callouts. */
.page-intro {
    font-size: 1.0rem;
    line-height: 1.85;
    color: var(--text);
    margin-bottom: 1.75rem;
}

/* Lead paragraph on section landings (/tools/, /simulators/,
   /education/) — opens with a single intro paragraph above the
   filter chips / card grid. Lighter font-weight than .page-intro
   (which is for education content pages); spans the full content
   column so it visually lines up with the card grid below rather
   than reading as a half-width fragment. The accent-coloured anchor
   scoped below covers inline links in landing leads without needing
   per-link inline styles. */
.landing-intro {
    font-weight: 300;
    font-size: 1.0rem;
    color: var(--text);
    margin-bottom: 2rem;
    line-height: 1.8;
}
.landing-intro a { color: var(--accent); }

/* ── TABS ── */
.tabs {
    display: flex;
    border-bottom: 1px solid var(--border);
    margin-bottom: 1.5rem;
}
.tab-btn {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.09em;
    padding: 0.55rem 1.1rem;
    border: none;
    background: none;
    color: var(--text-dim);
    cursor: pointer;
    border-bottom: 2px solid transparent;
    margin-bottom: -1px;
    transition: all 0.18s;
}
.tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }
.tab-btn:hover:not(.active) { color: var(--text); }
.tab-pane { display: none; }
.tab-pane.active { display: block; }

/* ── FORM ── */
.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
}
.field { display: flex; flex-direction: column; gap: 0.4rem; }

label,
.field-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-dim);
}

input[type="number"],
input[type="text"],
input[type="email"],
textarea,
select {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.55rem 0.75rem;
    font-family: var(--mono);
    font-size: 0.9rem;
    color: var(--text-bright);
    width: 100%;
    transition: border-color 0.18s, box-shadow 0.18s;
    -webkit-appearance: none;
}
textarea { resize: vertical; line-height: 1.6; min-height: 6rem; }
input:focus, textarea:focus, select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-dim);
}
select option { background: var(--surface); }

/* ── RESULT PANEL ── */
.result-panel {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 1.25rem 1.5rem;
    margin-top: 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}
.result-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-dim);
    margin-bottom: 0.2rem;
}
.result-value {
    font-family: var(--mono);
    font-size: 2rem;
    font-weight: 600;
    color: var(--blue);
    letter-spacing: -0.02em;
    font-variant-numeric: tabular-nums;
    transition: color 0.18s;
}
.result-value.error { color: var(--red); }
.result-value.muted { color: var(--text-dim); }

.result-formula {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-top: 0.75rem;
    padding-top: 0.75rem;
    border-top: 1px solid var(--border);
    font-style: italic;
    word-break: break-all;
}
/* .result-formula modifiers — formula blocks that need different layout
   chrome than the default. .flush drops the top margin and border so the
   formula sits flat under a tabbed Output panel (bacnet, signal-scaling
   slope/offset, thermistor). .wrap relaxes the default break-all so
   long readable expressions break on word boundaries instead of
   mid-token (signal-scaling Forward + Reverse panels). */
.result-formula.flush { margin: 0; padding: 0.7rem 1.25rem; }
.result-formula.wrap  { word-break: normal; overflow-wrap: break-word; }

/* ── RANGE BAR ── */
.range-bar-wrap { margin-top: 1rem; }
.range-bar-labels {
    display: flex;
    justify-content: space-between;
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-bottom: 0.35rem;
}
.range-bar {
    height: 5px;
    background: var(--border);
    border-radius: 3px;
    overflow: hidden;
}
.range-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--blue));
    border-radius: 3px;
    transition: width 0.2s ease;
    width: 0%;
}

/* ── BIT VIEWER ── */
/* p.bit-hint (not .bit-hint) so the rule ties .tool-body p on
   specificity and wins via cascade order. All current uses are on
   `<p>` — see also p.pid-note and p.ref-note below. */
p.bit-hint {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-bottom: 0.85rem;
}

.bit-grid {
    display: grid;
    grid-template-columns: repeat(16, 1fr);
    gap: 4px;
    margin-bottom: 1rem;
}

.bit {
    aspect-ratio: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 2px;
    cursor: pointer;
    transition: all 0.12s;
    user-select: none;
}
.bit:hover { border-color: var(--text-dim); }
.bit.on { background: var(--accent-dim); border-color: var(--accent); }

.bit-val {
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-dim);
    line-height: 1;
}
.bit.on .bit-val { color: var(--accent); }
.bit-idx {
    font-family: var(--mono);
    font-size: 0.48rem;
    color: var(--text-dim);
    opacity: 0.45;
    margin-top: 2px;
}

.bit-readouts {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.75rem;
}
.readout {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.65rem 0.85rem;
}
.readout-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-dim);
    margin-bottom: 0.25rem;
}
.readout-value {
    font-family: var(--mono);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-bright);
    word-break: break-all;
    font-variant-numeric: tabular-nums;
}

/* ── FOOTER — v2.0.0 status-bar treatment.
       Mono caps, --surface-2 background, an [OK] pill + site name on the
       left and version / build datestamp / heartbeat dot on the right.
       The dot pulses on a 2-second keyframe — GPU-cheap, honored by
       prefers-reduced-motion via the global block at the bottom of this
       file. */
footer {
    position: relative;
    z-index: 1;
    border-top: 1px solid var(--border);
    background: var(--surface-2);
    padding: 0.85rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;   /* full-bleed status bar — matches .site-nav */
    gap: 1rem;
}
.footer-left,
.footer-right {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
}
.footer-text {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-variant-numeric: tabular-nums;
}
.footer-text strong {
    color: var(--text);
    font-weight: 600;
}
.heartbeat-dot {
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--accent);
    animation: heartbeat 2s ease-in-out infinite;
}

/* ── ANIMATIONS ── */
@keyframes fadeUp {
    from { opacity: 0; transform: translateY(14px); }
    to   { opacity: 1; transform: translateY(0); }
}
/* v2.0.0 — `heartbeat` powers the footer dot and the About-card status
   row's live indicator. 2-second cycle, eased — a quiet "this system is
   running" cue. `breathe` is the slower 4-second version used on the
   .site-nav-brand span (.dev) — peripheral, never the focal point.
   Both are squashed by the global prefers-reduced-motion block at the
   bottom of this file. */
@keyframes heartbeat {
    0%, 100% { opacity: 1; }
    50%      { opacity: 0.35; }
}
@keyframes breathe {
    0%, 100% { opacity: 1; }
    50%      { opacity: 0.55; }
}

/* ── RESPONSIVE ── */
@media (max-width: 620px) {
    .form-row        { grid-template-columns: 1fr; }
    .bit-grid        { grid-template-columns: repeat(8, 1fr); }
    .bit-readouts    { grid-template-columns: 1fr 1fr; }
    .pid-controls    { grid-template-columns: 1fr; }
    .ref-table       { font-size: 0.76rem; }
    .ref-table th, .ref-table td { padding: 0.5rem 0.5rem; }
    .sim-canvas-wrap canvas { height: 200px; }
    .sim-legend      { gap: 1rem; }
    .site-nav        { padding: 0.7rem 1rem; }
    main             { padding-left: 1rem; padding-right: 1rem; }
    .hero            { margin-left: 1rem; margin-right: 1rem; width: auto; }
    .hero-body       { padding: 3rem 1.25rem 2.5rem; }
    .console-titlebar,
    .console-statusline { padding: 0.5rem 0.75rem; font-size: 0.62rem; }
    footer           { padding: 0.85rem 1rem; flex-direction: column; align-items: flex-start; gap: 0.5rem; }
    /* Long section-header labels would otherwise force horizontal scroll
       on narrow viewports because of the desktop white-space:nowrap.
       Allow wrapping below the mobile breakpoint — the trailing
       .section-line still sits centered alongside the wrapped label. */
    .section-label   { white-space: normal; }
}
/* ── COPY BUTTON ── */
.copy-btn {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 0.2rem 0.55rem;
    background: none;
    border: 1px solid var(--border);
    border-radius: 2px;
    color: var(--text-dim);
    cursor: pointer;
    transition: all 0.15s;
    white-space: nowrap;
}
.copy-btn:hover { border-color: var(--accent); color: var(--accent); }
.copy-btn.copied { border-color: var(--blue); color: var(--blue); }
.copy-btn.active { border-color: var(--accent); color: var(--accent); }

/* ── FULLSCREEN MODE ──
   Toggle button in the .tool-card corner pins the card to the viewport via
   .is-fullscreen. Wired by /scripts/fullscreen-toggle.js — pages opt in by
   adding a [data-fullscreen-target] button anywhere in the card. ESC exits.
   Add the .fs-desktop-only modifier on tools that don't make sense below
   the 1000px breakpoint (e.g. drag-wiring editors). */
.tool-card-fullscreen-btn {
    position: absolute;
    top: 0.55rem;
    right: 0.55rem;
    z-index: 2;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-family: var(--mono);
    font-size: 0.68rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 0.32rem 0.6rem 0.32rem 0.55rem;
    background: var(--surface);
    border: 1px solid var(--accent);
    border-radius: 2px;
    color: var(--accent);
    cursor: pointer;
    transition: color 0.15s, border-color 0.15s, background 0.15s;
}
.tool-card-fullscreen-btn:hover { background: var(--accent-soft); }
.tool-card-fullscreen-btn svg { width: 0.85rem; height: 0.85rem; display: block; }
.tool-card-fullscreen-btn .fs-icon-exit,
.tool-card-fullscreen-btn .fs-label-exit { display: none; }
.tool-card.is-fullscreen .tool-card-fullscreen-btn .fs-icon-enter,
.tool-card.is-fullscreen .tool-card-fullscreen-btn .fs-label-enter { display: none; }
.tool-card.is-fullscreen .tool-card-fullscreen-btn .fs-icon-exit  { display: block; }
.tool-card.is-fullscreen .tool-card-fullscreen-btn .fs-label-exit { display: inline; }
@media (max-width: 999px) {
    .tool-card-fullscreen-btn.fs-desktop-only { display: none; }
}

.tool-card.is-fullscreen {
    position: fixed;
    inset: 0;
    z-index: 300;                  /* above .site-nav (100) and .skip-link (200) */
    margin: 0;
    border: 0;
    border-radius: 0;
    max-width: none;
    overflow: auto;
}
/* The "← All tools" / "← All simulators" back-link sits as a sibling of
   .tool-card inside <main>. Hide it when its preceding sibling is the
   fullscreen card — back-navigation makes no sense in fullscreen. */
.tool-card.is-fullscreen + .back-link,
.tool-card.is-fullscreen ~ .back-link { display: none; }

body.has-fullscreen-tool { overflow: hidden; }
/* In fullscreen the .tool-card overlay covers everything, but leave the
   nav and footer in place in the DOM — they're hidden by the overlay,
   not removed. The <main> element creates a stacking context of its own
   (position: relative + z-index: 1) so a fixed-positioned card inside it
   can't out-rank .site-nav (z-index: 100) on its own merits — its z-index
   only applies *within* main's context. Lift main above the nav (and
   footer, z-index: 1) while a tool is fullscreen. */
body.has-fullscreen-tool main { z-index: 400; }

/* ── SUBHEAD (within a tool body) ── */
.subhead {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--accent);
    margin: 2rem 0 0.9rem;
}
.subhead:first-child { margin-top: 0; }

/* ── PID SIM ── */
.pid-controls {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 1.25rem 1.5rem;
    margin-bottom: 1.25rem;
}
.slider-field { display: flex; flex-direction: column; gap: 0.45rem; }
.slider-head {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: baseline;
    gap: 0.15rem 0.5rem;
}
.slider-val { font-family: var(--mono); font-size: 0.8rem; color: var(--accent); }
.slider-sub {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    letter-spacing: 0.02em;
}

input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 4px;
    background: var(--border);
    border-radius: 3px;
    outline: none;
    cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--bg);
    box-shadow: 0 0 0 1px var(--accent);
}
input[type="range"]::-moz-range-thumb {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--bg);
    box-shadow: 0 0 0 1px var(--accent);
}

/* ── FOCUS INDICATORS ──
   Every custom-styled interactive with a :hover needs a paired
   :focus-visible — the browser default outline is suppressed by the
   `outline: none` on .skip-link / inputs / the range track. Add new
   custom interactives to this block. */
.copy-btn:focus-visible,
.tab-btn:focus-visible,
.units-btn:focus-visible,
.cta-button:focus-visible,
.back-link:focus-visible,
.filter-chip:focus-visible,
.nav-card:focus-visible,
.related-links a:focus-visible,
.tool-card-fullscreen-btn:focus-visible,
.quiz-choice:focus-visible,
.quiz-action:focus-visible,
.quiz-reset-best:focus-visible,
.quiz-restart-now:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;   /* v2.0.0 — was 2px; lifted so the accent ring no longer kisses the border on .nav-card */
}
input[type="range"]:focus-visible::-webkit-slider-thumb {
    box-shadow: 0 0 0 1px var(--accent), 0 0 0 4px var(--accent-glow);
}
input[type="range"]:focus-visible::-moz-range-thumb {
    box-shadow: 0 0 0 1px var(--accent), 0 0 0 4px var(--accent-glow);
}

/* ── TOUCH-TARGET FLOOR ──
   On touch devices (coarse pointer, no hover), the chrome-level
   controls — top-nav links, units toggle, tool tabs, quiz settings —
   are padded to a >=44px hit area (WCAG 2.5.5 / Apple HIG). Scoped to
   (hover: none) so pointer users keep the compact desktop workstation
   density; the answer-level controls (.quiz-choice, .quiz-action,
   .ps-input, copy/submit buttons) already clear 44px and aren't
   repeated here. Like FOCUS INDICATORS above, this is the single
   consolidated home for the floor — add new chrome-level interactives
   here rather than scattering per-component min-heights.
   See codebase-issues #74 / ux-audit #3 / #8 / #9 for the why. */
@media (hover: none) {
    .site-nav-links a,
    .units-btn,
    .tab-btn,
    .quiz-reset-best {
        display: inline-flex;
        align-items: center;
        justify-content: center;
        min-height: 44px;
    }
    .site-nav-links a { padding-inline: 0.2rem; }
    .quiz-settings-select { min-height: 44px; }
}

/* default top spacing matches the dominant calc/converter shape:
   data row above, button row below. The .ps-row exception keeps
   toggle groups (Look up by, Chart range) vertically centered with
   their label sibling — .ps-row's grid + align-items: center would
   otherwise offset the buttons by ~0.5rem. */
.btn-row { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 1rem; }
.ps-row > .btn-row { margin-top: 0; }

.sim-canvas-wrap {
    position: relative;            /* anchor for absolute-positioned overlays (e.g. psychrometric chart's state-point chip) */
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.75rem 0.5rem;
    margin-bottom: 0.75rem;
}
.sim-canvas-wrap canvas { display: block; width: 100%; height: 260px; }
.sim-legend {
    display: flex;
    gap: 1.5rem;
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-bottom: 1rem;
    padding-left: 0.25rem;
}
.sim-legend .swatch {
    display: inline-block;
    width: 18px;
    height: 0;
    vertical-align: middle;
    margin-right: 0.45rem;
}
.sim-legend .swatch.pv { border-top: 2px solid var(--accent); }
.sim-legend .swatch.sp { border-top: 2px dashed var(--text-dim); }

.readout-value.warn { color: var(--red); }

/* ── REFERENCE TABLE (property-sheet style) ── */
.ref-table { width: 100%; border-collapse: collapse; font-size: 0.82rem; }
.ref-table th, .ref-table td {
    text-align: left;
    padding: 0.6rem 0.75rem;
    border-bottom: 1px solid var(--border);
    vertical-align: top;
    line-height: 1.55;
}
.ref-table thead th {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-dim);
    font-weight: 400;
    background: var(--surface-2);
    border-bottom: 1px solid var(--border);
}
.ref-table tbody tr:nth-child(even) { background: var(--surface-2); }
.ref-table tbody tr:hover { background: rgba(21,119,184,0.07); }
.ref-table td:first-child { color: var(--text-bright); }
.ref-table tbody tr:last-child td { border-bottom: none; }

/* ── CALLOUT CARDS (PID-term cards, worked-example asides, discovery
   prompts, Easter-egg reveals — same visual treatment everywhere) ── */
.callout-grid { display: grid; gap: 1rem; }
.callout {
    background: var(--bg);
    border: 1px solid var(--border);
    border-left: 2px solid var(--accent);
    border-radius: 3px;
    padding: 1rem 1.25rem;
}
.callout h3 {
    font-family: var(--mono);
    font-size: 0.8rem;
    color: var(--text-bright);
    margin: 0 0 0.45rem;
    font-weight: 600;
}
.callout h3 span { color: var(--text-dim); font-weight: 400; }
.callout p { font-size: 0.86rem; line-height: 1.7; }
.callout em { color: var(--text-bright); font-style: normal; }

/* ── NARROW-WIDTH ORIENTATION NOTE — hidden by default; pages flip to
   display:block inside their own @media at whatever breakpoint their
   layout shifts. Frames a layout change as mental-model orientation,
   NOT as apology. Voice reference: function-block-editor.html. ── */
.narrow-width-note {
    display: none;
    font-size: 0.8rem;
    color: var(--text-dim);
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.6rem 0.8rem;
    margin: 0.6rem 0;
}

p.pid-note {
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--text-dim);
    line-height: 1.75;
    margin-top: 1.25rem;
}

/* ──────────────────────────────────────────────────────────────────────
 * LANDING-PAGE CARDS — the clickable tiles on the home page and the
 * Tools / Education landings. Link-shaped cards with a tag, title,
 * and short description.
 * ────────────────────────────────────────────────────────────────────── */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 1rem;
    margin-bottom: 2.5rem;
}
.card-grid.two { grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }

/* Filter chip row above the .card-grid on /tools/ and /education/.
   Each chip toggles which .nav-card[data-category] is visible; URL hash
   tracks state. Chips are <button>s with a mono pill shape — same
   family as the .nav-card-pill statusline items, just larger and
   stateful. */
.filter-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-bottom: 1.5rem;
}

/* ── CHIP-ROW PREAMBLE ── Soft one-liner above a .filter-chips row.
   Element-qualified p. per site convention so .tool-body p doesn't
   out-cascade it. Mirrors p.bit-hint's shape (small mono dim text)
   with tighter bottom-margin since it sits flush above the chips. */
p.chip-row-preamble {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-bottom: 0.5rem;
}
.filter-chip {
    display: inline-flex;
    align-items: baseline;
    gap: 0.4rem;
    font-family: var(--mono);
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.35rem 0.75rem;
    cursor: pointer;
    transition: border-color 0.18s, background 0.18s, color 0.18s;
}
.filter-chip:hover { border-color: var(--accent); color: var(--accent); }
.filter-chip.active {
    color: var(--accent);
    background: var(--accent-dim);
    border-color: var(--accent-glow);
}
.filter-chip-count {
    font-size: 0.65rem;
    color: var(--text-dim);
}
.filter-chip.active .filter-chip-count { color: var(--accent); opacity: 0.75; }
/* The .nav-card rule below sets display:block, which would override the UA
   `hidden { display: none }` and leave hidden cards consuming grid slots.
   Re-assert display: none for the [hidden] case. */
.nav-card[hidden] { display: none; }

/* v2.1.0 — nav cards moved from a flat surface+padding shape to a
   faux-instrument frame that mirrors the home hero (.console-titlebar
   + body + .console-statusline). The outer .nav-card supplies the
   chrome; the inner .nav-card-body carries the prose. Section accent
   (--section-accent) defaults to --accent and is overridden by the
   --tools / --education / --simulators / --home modifier so the
   hover border, name color, and status pill all track the section's
   identity color (matches the gutter motif palette). See
   _includes/nav-card.njk for the macro that emits the chrome — pages
   call it instead of hand-rolling the markup. */
.nav-card {
    --section-accent:      var(--accent);
    --section-accent-dim:  var(--accent-dim);
    --section-accent-glow: var(--accent-glow);
    display: flex;
    flex-direction: column;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 0;
    overflow: hidden;
    text-decoration: none;
    color: inherit;
    transition: border-color 0.18s, transform 0.18s;
}
.nav-card--tools      { --section-accent: var(--accent); --section-accent-dim: var(--accent-dim); --section-accent-glow: var(--accent-glow); }
.nav-card--education  { --section-accent: var(--plum);   --section-accent-dim: var(--plum-dim);   --section-accent-glow: var(--plum-glow); }
.nav-card--simulators { --section-accent: var(--teal);   --section-accent-dim: var(--teal-dim);   --section-accent-glow: var(--teal-glow); }
.nav-card--practice   { --section-accent: var(--amber);  --section-accent-dim: var(--amber-dim);  --section-accent-glow: var(--amber-glow); }
.nav-card--home       { --section-accent: var(--accent); --section-accent-dim: var(--accent-dim); --section-accent-glow: var(--accent-glow); }

.nav-card:hover { border-color: var(--section-accent); transform: translateY(-2px); }

/* Card chrome — sized down from the hero (.console-titlebar /
   .console-statusline) so a grid of cards stays readable. Smaller
   padding, smaller font, same vocabulary. */
.nav-card-titlebar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    padding: 0.45rem 0.85rem;
    border-bottom: 1px solid var(--border);
    background: var(--surface-2);
    font-family: var(--mono);
    font-size: 0.62rem;
    color: var(--text);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}
/* Title text must single-line — the 4-col card grid at 1920px viewport
   only leaves ~195px for the title beside the right-side status pill,
   and a wrapped titlebar pushes the body down inconsistently across
   the grid. titleShort values in the partial are trimmed to fit; this
   ellipsis safety catches anything that still spills over (a long
   future name, an unforeseen viewport). `min-width:0` is required for
   text-overflow to take effect inside a flex parent — without it the
   span won't shrink below its intrinsic width. */
.nav-card-titlebar > span:first-child {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    min-width: 0;
}
.nav-card-titlebar .titlebar-dots {
    color: var(--text-dim);
    margin: 0 0.35rem;
}
.nav-card-titlebar .ok-pill {
    /* Per-section status-pill tint. Same .ok-pill shape as the hero;
       the colors come from the .nav-card--<section> tokens above. */
    background: var(--section-accent-dim);
    color: var(--section-accent);
    border-color: var(--section-accent-glow);
}
.nav-card-titlebar .ok-pill::before {
    background: var(--section-accent);
}

.nav-card-body {
    padding: 1.1rem 1.2rem;
    flex: 1;
}

.nav-card-statusline {
    padding: 0.5rem 1rem;
    border-top: 1px solid var(--border);
    background: var(--surface-2);
    font-family: var(--mono);
    font-size: 0.6rem;
    color: var(--text-dim);
    letter-spacing: 0.07em;
    text-transform: uppercase;
    font-variant-numeric: tabular-nums;
}
.nav-card-pill {
    display: inline;
}
.nav-card-pill:not(:last-child)::after {
    content: '•';
    margin: 0 0.35rem;
    color: var(--border);
}

.nav-card-name {
    font-family: var(--mono);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-bright);
    margin-bottom: 0.4rem;
    transition: color 0.18s;
}
.nav-card:hover .nav-card-name { color: var(--section-accent); }
.nav-card-desc {
    font-size: 0.95rem;
    color: var(--text);
    line-height: 1.65;
}

/* ──────────────────────────────────────────────────────────────────────
 * ABOUT-CARD REBUILD — v2.0.0 home page only
 * The home's About panel reframes the wall-of-prose pattern as a BAS-
 * inspector view: a property-sheet header (role / location / industry /
 * verified / status) followed by a recessed prose block (`.about-prose`)
 * with a blue left rule — the same shape as `.widget-anecdote`. The
 * `.live` modifier on a `.ps-value` adds a pulsing accent dot to signal
 * a "running" state, reused from the same `heartbeat` keyframe that
 * drives the footer dot.
 * Only `html/index.html` uses these today. Internals here are the
 * decoration layered on top of the shared `.ps-row` / `.ps-label` /
 * `.ps-value` vocabulary.
 * ────────────────────────────────────────────────────────────────────── */
.about-rebuild .ps-row {
    padding: 9px 1.25rem;
}
.about-rebuild .ps-row:first-child { padding-top: 1rem; }
.about-rebuild .ps-row:last-of-type {
    border-bottom: 1px solid var(--border);
}
.about-rebuild .ps-value.live {
    color: var(--accent);
    font-weight: 600;
}
.about-rebuild .ps-value.live::before {
    content: "";
    display: inline-block;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent);
    margin-right: 0.4rem;
    vertical-align: middle;
    animation: heartbeat 2s ease-in-out infinite;
}
.about-prose {
    margin: 1rem 1.25rem 1.25rem;
    padding: 0.85rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-left: 3px solid var(--blue);
    border-radius: 3px;
    font-size: 0.92rem;
    line-height: 1.75;
    color: var(--text);
}
.about-prose p + p { margin-top: 0.85rem; }
.about-prose a { color: var(--accent); }
.about-prose .colophon {
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--text-dim);
    margin-top: 1rem;
}

/* ──────────────────────────────────────────────────────────────────────
 * BACK LINK — the small "← All tools" / "← Back to …" anchor that lives
 * under a tool's .tool-card. Kept as its own class so the size and color
 * are consistent across pages (and easy to bump from one place).
 * ────────────────────────────────────────────────────────────────────── */
.back-link {
    display: inline-block;
    margin-top: 1.75rem;
    font-family: var(--mono);
    font-size: 0.85rem;
    color: var(--accent);
    text-decoration: none;
    transition: color 0.18s;
}
.back-link:hover { color: var(--text-bright); }

/* ──────────────────────────────────────────────────────────────────────
 * RELATED LINKS — end-of-page cross-links to topically related tools,
 * simulators, and lessons. SEO topic-clustering signal that also helps
 * a reader navigate sideways instead of bouncing back to a landing.
 * Rendered by html/_includes/related-links.njk; sits inside <main>
 * directly above .back-link.
 * ────────────────────────────────────────────────────────────────────── */
.related-links {
    margin-top: 2rem;
    padding: 1.1rem 1.5rem 1.2rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1.1rem 2.5rem;
}
.related-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--accent);
    margin: 0 0 0.6rem;
}
.related-links ul {
    list-style: none;
    padding: 0;
    margin: 0;
    font-size: 0.9rem;
    line-height: 1.7;
}
.related-links li {
    padding-left: 0.95rem;
    position: relative;
}
.related-links li::before {
    content: "→";
    position: absolute;
    left: 0;
    color: var(--accent);
    font-family: var(--mono);
}
.related-links a {
    color: var(--text);
    text-decoration: none;
    border-bottom: 1px dotted var(--border);
    transition: color 0.18s, border-color 0.18s;
}
.related-links a:hover {
    color: var(--accent);
    border-color: var(--accent);
}

/* ──────────────────────────────────────────────────────────────────────
 * PRACTICE / QUIZ — the engine in /scripts/quiz-engine.js renders the
 * shell described here inside the page's <div id="quiz"></div>. Pages
 * provide only the empty container + the questions array + the call to
 * Quiz.mount. The accent for the Practice section comes from --amber
 * (see .nav-card--practice above).
 *
 * Visual vocabulary: choices are .quiz-choice buttons styled in the
 * same family as .filter-chip / .units-btn — hairline border, mono
 * caps off here since choice text is sentence-case. Selected and post-
 * reveal correct / wrong states get accent / red borders. Reveal panel
 * borrows the .callout left-bar treatment with --correct (accent) and
 * --incorrect (red) variants. Results card uses .ref-table-dense for
 * the miss list to match the rest of the site's reference-table look.
 * ────────────────────────────────────────────────────────────────────── */

.quiz { display: block; }

.quiz-settings {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.6rem 1rem;
    margin-bottom: 1.25rem;
    padding-bottom: 0.85rem;
    border-bottom: 1px solid var(--border-faint);
    font-family: var(--mono);
    font-size: 0.78rem;
    color: var(--text-dim);
}
.quiz-settings-label {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}
.quiz-settings-select {
    font-family: var(--mono);
    font-size: 0.78rem;
    color: var(--text);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.2rem 0.5rem;
}
.quiz-best-readout {
    margin-left: auto;          /* push to the right on wide; wraps below on narrow */
    font-size: 0.74rem;
    letter-spacing: 0.04em;
    color: var(--text);
    font-variant-numeric: tabular-nums;
}
.quiz-reset-best {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-dim);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.25rem 0.6rem;
    cursor: pointer;
    transition: border-color 0.18s, color 0.18s;
}
.quiz-reset-best:hover { border-color: var(--accent); color: var(--accent); }

.quiz-dirty-notice {
    margin: 0 0 1rem;
    padding: 0.55rem 0.85rem;
    background: var(--amber-dim);
    border: 1px solid var(--amber-glow);
    border-radius: 3px;
    font-family: var(--mono);
    font-size: 0.74rem;
    color: var(--text);
    display: flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
}
.quiz-restart-now {
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--amber);
    background: transparent;
    border: 1px solid var(--amber);
    border-radius: 3px;
    padding: 0.2rem 0.55rem;
    cursor: pointer;
    transition: color 0.18s, background 0.18s;
}
.quiz-restart-now:hover { color: var(--surface); background: var(--amber); }
/* The dirty-notice and numeric rows below set display: flex / inline-flex,
   which would override the UA-default `[hidden] { display: none }`. Same
   trap that .nav-card[hidden] solves above — re-assert hidden for the
   elements the engine toggles via the `hidden` attribute. */
.quiz-dirty-notice[hidden],
.quiz-numeric[hidden] { display: none; }

.quiz-progress {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
    margin-bottom: 1.4rem;
}
.quiz-progress-text {
    font-family: var(--mono);
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-dim);
    margin: 0;
}
.quiz-progress-bar {
    height: 4px;
    background: var(--surface-3);
    border-radius: 2px;
    overflow: hidden;
}
.quiz-progress-fill {
    height: 100%;
    width: 0%;
    background: var(--amber);
    /* Global @media (prefers-reduced-motion: reduce) below squashes
       transitions to 0.01ms — no defensive selector needed here. */
    transition: width 220ms ease;
}

.quiz-question-pane {
    display: flex;
    flex-direction: column;
    gap: 1.1rem;
}
.quiz-prompt {
    font-size: 1.05rem;
    line-height: 1.7;
    color: var(--text);
}
.quiz-prompt code {
    font-family: var(--mono);
    font-size: 0.92em;
    background: var(--surface-3);
    padding: 0.05em 0.35em;
    border-radius: 2px;
}

.quiz-snippet-slot { margin: 0; }
.quiz-snippet {
    font-family: var(--mono);
    font-size: 0.82rem;
    line-height: 1.55;
    color: var(--text);
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.85rem 1rem;
    white-space: pre;
    overflow-x: auto;
}

.quiz-choices {
    display: flex;
    flex-direction: column;
    gap: 0.55rem;
}
.quiz-choice {
    display: block;
    width: 100%;
    text-align: left;
    font-family: var(--sans);
    font-size: 0.95rem;
    line-height: 1.55;
    color: var(--text);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.7rem 0.95rem;
    cursor: pointer;
    transition: border-color 0.18s, background 0.18s, color 0.18s;
}
.quiz-choice code {
    font-family: var(--mono);
    font-size: 0.9em;
    background: var(--surface-3);
    padding: 0.02em 0.3em;
    border-radius: 2px;
}
.quiz-choice:hover { border-color: var(--amber); }
.quiz-choice[aria-checked="true"],
.quiz-choice.selected {
    border-color: var(--amber);
    background: var(--amber-dim);
    color: var(--text-bright);
}
.quiz-choice[aria-disabled="true"],
.quiz-choice:disabled {
    cursor: default;
    opacity: 0.7;
}
.quiz-choice.correct {
    border-color: var(--accent);
    background: var(--accent-dim);
    color: var(--text-bright);
    opacity: 1;
}
.quiz-choice.wrong {
    border-color: var(--red);
    background: rgba(196,56,47,0.10);
    color: var(--text-bright);
    opacity: 1;
}

.quiz-numeric {
    display: inline-flex;
    align-items: baseline;
    gap: 0.5rem;
}
.quiz-numeric-input {
    font-family: var(--mono);
    font-size: 1rem;
    color: var(--text);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 3px;
    padding: 0.5rem 0.75rem;
    width: 9rem;
}
.quiz-numeric-input:focus {
    outline: none;
    border-color: var(--amber);
    box-shadow: 0 0 0 2px var(--amber-glow);
}
.quiz-numeric-unit {
    font-family: var(--mono);
    font-size: 0.85rem;
    color: var(--text-dim);
}
.quiz-numeric.correct .quiz-numeric-input { border-color: var(--accent); background: var(--accent-dim); }
.quiz-numeric.wrong .quiz-numeric-input { border-color: var(--red); background: rgba(196,56,47,0.10); }

.quiz-actions {
    display: flex;
    flex-wrap: wrap;
    justify-content: flex-end;
    gap: 0.6rem;
    margin-top: 1.4rem;
}
.quiz-action {
    font-family: var(--mono);
    font-size: 0.85rem;
    letter-spacing: 0.02em;
    padding: 0.6rem 1.2rem;
    border-radius: 3px;
    cursor: pointer;
    transition: color 0.18s, background 0.18s, border-color 0.18s;
}
.quiz-action-primary {
    color: var(--surface);
    background: var(--amber);
    border: 1px solid var(--amber);
}
.quiz-action-primary:hover { background: var(--text-bright); border-color: var(--text-bright); }
.quiz-action-primary:disabled {
    cursor: not-allowed;
    opacity: 0.45;
}
.quiz-action-secondary {
    color: var(--text-dim);
    background: var(--surface);
    border: 1px solid var(--border);
}
.quiz-action-secondary:hover { color: var(--text); border-color: var(--text-dim); }
.quiz-action-secondary:disabled {
    cursor: not-allowed;
    opacity: 0.45;
}

.quiz-reveal {
    margin-top: 1.2rem;
    padding: 0 0 0 1rem;
    border-left: 2px solid transparent;
    /* The panel exists in the DOM at all times so aria-live announces
       on content change, not on insertion. Empty state has no visible
       chrome — only the .--correct / .--incorrect modifiers paint a
       border. */
}
.quiz-reveal:empty { padding: 0; border-left-color: transparent; }
.quiz-reveal--correct { border-left-color: var(--accent); }
.quiz-reveal--incorrect { border-left-color: var(--red); }
.quiz-reveal-status {
    font-family: var(--mono);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin: 0 0 0.55rem;
    color: var(--text-dim);
}
.quiz-reveal--correct .quiz-reveal-status { color: var(--accent); }
.quiz-reveal--incorrect .quiz-reveal-status { color: var(--red); }
.quiz-reveal-right {
    font-size: 0.9rem;
    color: var(--text);
    margin: 0 0 0.6rem;
}
.quiz-reveal-explain {
    font-size: 0.92rem;
    line-height: 1.65;
    color: var(--text);
}
.quiz-reveal-explain p + p { margin-top: 0.6rem; }
.quiz-reveal-explain code {
    font-family: var(--mono);
    font-size: 0.9em;
    background: var(--surface-3);
    padding: 0.05em 0.35em;
    border-radius: 2px;
}
.quiz-reveal-learn-more {
    font-family: var(--mono);
    font-size: 0.78rem;
    margin-top: 0.7rem;
    color: var(--text-dim);
}
.quiz-reveal-learn-more a {
    color: var(--accent);
    text-decoration: none;
    border-bottom: 1px dotted var(--border);
}
.quiz-reveal-learn-more a:hover {
    border-color: var(--accent);
}

.quiz-results {
    padding: 1.5rem 0.25rem 0.5rem;
    text-align: center;
}
.quiz-results-headline {
    font-family: var(--mono);
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--text-bright);
    margin: 0 0 0.35rem;
    font-variant-numeric: tabular-nums;
}
.quiz-results-sub {
    font-family: var(--mono);
    font-size: 0.82rem;
    color: var(--text-dim);
    margin: 0 0 1.6rem;
}
.quiz-results-newbest {
    color: var(--amber);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 0.74rem;
}
.quiz-results-misses-heading {
    font-family: var(--mono);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-dim);
    margin: 0 0 0.65rem;
    text-align: left;
}
.quiz-results-misses {
    text-align: left;
    margin-bottom: 1.4rem;
}
.quiz-results-misses td { vertical-align: top; }
.quiz-results-misses a { color: var(--accent); text-decoration: none; border-bottom: 1px dotted var(--border); }
.quiz-results-misses a:hover { border-color: var(--accent); }
.quiz-results-actions { justify-content: center; }
.quiz-restart-btn { background: var(--amber); border-color: var(--amber); color: var(--surface); }
.quiz-restart-btn:hover { background: var(--text-bright); border-color: var(--text-bright); }

/* Narrow viewports — stack the action row full-width so a thumb can
   reach both buttons; settings wrap onto multiple lines. The
   .quiz-best-readout flex auto-margin already drops it below on wrap. */
@media (max-width: 560px) {
    .quiz-actions {
        flex-direction: column;
        align-items: stretch;
    }
    .quiz-action { width: 100%; }
}

/* ──────────────────────────────────────────────────────────────────────
 * CTA BUTTON — a prominent in-page link styled like a primary button.
 * Used for "Try it for yourself →" and other end-of-page calls to action.
 * ────────────────────────────────────────────────────────────────────── */
.cta-button {
    display: inline-block;
    font-family: var(--mono);
    font-size: 0.85rem;
    font-weight: 500;
    letter-spacing: 0.02em;
    padding: 0.7rem 1.4rem;
    background: var(--surface);
    border: 1px solid var(--accent);
    border-radius: 3px;
    color: var(--accent);
    text-decoration: none;
    transition: background 0.18s, color 0.18s;
}
.cta-button:hover { background: var(--accent); color: var(--surface); }

/* ──────────────────────────────────────────────────────────────────────
 * THREE-COLUMN PROPERTY-SHEET LAYOUT
 *
 * A denser "workstation-tool" layout for tools where input / output /
 * reference make sense as three distinct surfaces side by side, rather
 * than stacked. Borrows Niagara's property-sheet grammar: label-LEFT /
 * value-RIGHT rows with hairline dividers, small-caps section headers, a
 * recessed reference panel ALONGSIDE the active tool, dense tables. See
 * site-ideas-and-friction.md → "Visual design — two products, one
 * codebase" for the higher-level design philosophy this pattern serves.
 *
 * Adopters: tools/bacnet-ip-converter.html, tools/signal-scaling.html,
 * tools/modbus-register-viewer.html. The PID tuner (tools/pid-tuner.html)
 * deliberately keeps its custom stacked layout — its simulator (canvas +
 * sliders + parameter-style selector + preset chips + metrics) doesn't fit
 * the Input / Output / Reference shape without forcing it; only its
 * symptom → tuning-move cheat sheet adopts the .ref-table-dense styling.
 * ────────────────────────────────────────────────────────────────────── */

/* the grid: three equal columns, butting against the card edges (no gap).
   Each section carries its own padding; the last one is the recessed
   reference panel. Lives directly inside a .tab-pane (or .tool-card), not
   inside a padded .tool-body. */
.tool-body-3col {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
}
.tool-body-3col > section {
    padding: 1.25rem 1.25rem 1.5rem;
    border-right: 1px solid var(--border);
}
.tool-body-3col > section:last-child {
    border-right: none;
    background: var(--surface-3);
}

/* same shape, two equal columns — for tools whose reference content lives
   in a sibling .tool-card rather than the third column (e.g. the BACnet
   converter). No recessed last-child since there is no reference panel. */
.tool-body-2col {
    display: grid;
    grid-template-columns: 1fr 1fr;
}
.tool-body-2col > section {
    padding: 1.25rem 1.25rem 1.5rem;
    border-right: 1px solid var(--border);
}
.tool-body-2col > section:last-child { border-right: none; }

/* Full-width sibling row that sits below a .tool-body-2col grid. Same
   recessed surface + top border as the .tool-body-3col reference column —
   used when a sparse Output column would leave a dense reference / worked-
   example column visually orphaned at the right. No grid template to
   collapse, so no responsive variant needed; the parent (.tab-pane or
   .tool-card) already handles viewport-width changes. */
.tool-body-row {
    padding: 1.25rem 1.25rem 1.5rem;
    border-top: 1px solid var(--border);
    background: var(--surface-3);
}

/* tabs sitting directly above a .tool-body-3col: inset the buttons to line
   up with the column padding, drop the bottom margin so the grid butts
   right up under the tab strip. (The .tab-btn underline indicator is
   unchanged — see the .tabs / .tab-btn rules above.) */
.tabs.tabs-flush { padding: 0 1.25rem; margin-bottom: 0; }

/* small-caps column header inside a 3-col body (INPUT / OUTPUT / …).
   (The redesign mockup called this `.section-label`; renamed to
   .ps-section-label to avoid colliding with the existing page-level
   .section-label used in .section-header.) */
.ps-section-label {
    font-family: var(--sans);
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--text-dim);
    letter-spacing: 0.12em;
    text-transform: uppercase;
    margin: 0 0 0.85rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
}

/* property-sheet row: label on the left, value or input on the right,
   faint hairline between rows. The Niagara-grammar replacement for the
   stacked layout's label-above-input .form-row / .field. */
.ps-row {
    display: grid;
    grid-template-columns: minmax(90px, 38%) 1fr;
    gap: 12px;
    padding: 9px 0;
    border-bottom: 1px solid var(--border-faint);
    align-items: center;
    min-height: 38px;
}
.ps-row:last-of-type { border-bottom: none; }
.ps-label {
    font-family: var(--sans);
    font-size: 0.82rem;
    color: var(--text-dim);
    text-transform: none;
    letter-spacing: normal;
}
.ps-value {
    font-family: var(--mono);
    font-size: 0.82rem;
    color: var(--text);
    font-variant-numeric: tabular-nums;
}
/* a live / actionable output value. (The mockup called this modifier
   `.readout`; renamed to `.live` because there is already a global
   `.readout` box class — see the bit-viewer / PID-metrics section above —
   that an element with both classes would inherit.) */
.ps-value.live {
    color: var(--blue);
    font-weight: 600;
    font-size: 0.92rem;
    overflow-wrap: anywhere;
}
.ps-value.error { color: var(--red); }  /* out-of-range output (placed after .live so it wins the colour) */
.ps-value.muted {                       /* a note, an absent value, a placeholder */
    color: var(--text-dim);
    font-family: var(--sans);
    font-style: italic;
    font-size: 0.78rem;
}
/* the input variant for a .ps-row's value cell — works on <input>, <select>
   and <textarea>. The element-qualified selectors (not bare `.ps-input`)
   outrank the global `input[type=…]` / `select` block above so the denser
   sizing wins. */
input.ps-input, select.ps-input, textarea.ps-input {
    width: 100%;
    padding: 5px 8px;
    border: 1px solid var(--border);
    background: var(--bg);
    font-family: var(--mono);
    font-size: 0.82rem;
    color: var(--text-bright);
    border-radius: 2px;
    -webkit-appearance: none;
}
input.ps-input:focus, select.ps-input:focus, textarea.ps-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: none;                   /* the dense layout uses a border change, not the glow */
}

/* dense reference table — tighter rows than .ref-table, sans-caps headers,
   for lookup data that lives in a side panel rather than the main flow. */
.ref-table-dense {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.78rem;
}
.ref-table-dense th {
    text-align: left;
    font-family: var(--sans);
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--text-dim);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    padding: 6px 8px;
    border-bottom: 1px solid var(--border);
    background: var(--surface-2);
}
.ref-table-dense td {
    padding: 5px 8px;
    border-bottom: 1px solid var(--border-faint);
    font-family: var(--mono);
    color: var(--text);
}
.ref-table-dense td.use {               /* a prose "typical use" cell, not data */
    font-family: var(--sans);
    font-size: 0.78rem;
    color: var(--text-dim);
}
.ref-table-dense tbody tr:nth-child(even) td { background: rgba(0,0,0,0.015); }
.ref-table-dense tbody tr:last-child td { border-bottom: none; }

/* a short explanatory note under a reference table. */
p.ref-note {
    font-family: var(--sans);
    font-size: 0.74rem;
    color: var(--text-dim);
    line-height: 1.55;
    margin-top: 0.85rem;
    padding-top: 0.85rem;
    border-top: 1px solid var(--border-faint);
}
/* worked-example pair — .worked-intro paragraph + .worked-list <ol>
   sit together inside a "Worked example" .tool-body-row section. The
   intro paragraph kills the base ref-note's top spacing (the section
   label above already provides it); the list adds its own indent. */
p.ref-note.worked-intro { margin-top: 0; }
ol.ref-note.worked-list { padding-left: 1.2em; }
/* compact ref-note variant for mini-sim captions sitting tight under
   a canvas readout — drops the base rule's border + heavy top spacing. */
p.ref-note.compact {
    margin-top: 0.5rem;
    padding-top: 0;
    border-top: none;
}

/* mobile / responsive — collapse the multi-column grids to a single stack
   (Input → Output → Reference). 3-col collapses earlier (≤1000px) than
   2-col (≤900px): three columns at the new 1120px main cap still leave
   each column ~340px, but at viewport ~1000px (1120px container minus
   side padding minus borders) each column is back to today's cramped
   ~290px. Collapsing 3-col at 1000px keeps psychrometric-chart /
   thermistor-calculator readable on narrow desktops and tablets. 2-col
   tools have headroom and only need to collapse at the tablet break.
   The "two products, one codebase" plan eventually wants a purpose-built
   mobile experience for these tools; this is the conservative pass.
   // mobile-first treatment of this tool is a future task — see site-ideas-and-friction.md */
@media (max-width: 1000px) {
    .tool-body-3col { grid-template-columns: 1fr; }
    .tool-body-3col > section { border-right: none; border-bottom: 1px solid var(--border); }
    .tool-body-3col > section:last-child { border-bottom: none; }
}
@media (max-width: 900px) {
    .tool-body-2col { grid-template-columns: 1fr; }
    .tool-body-2col > section { border-right: none; border-bottom: 1px solid var(--border); }
    .tool-body-2col > section:last-child { border-bottom: none; }
}

/* ──────────────────────────────────────────────────────────────────────
 * EDUCATION-PAGE SVG DIAGRAMS
 *
 * Shared block + legend for hand-written inline schematics on Education
 * pages with pipe-flow diagrams. Consolidated from the per-page
 * .hd-svg / .lp-svg rules once the third page with pipe-flow diagrams
 * (education/pump-control.html) landed — the trigger called out in the
 * friction file's load-piping entry.
 *
 * Supply piping is solid + --blue; return piping is dashed + --blue-cool
 * — distinguishable without colour. Element-level fallbacks (literal
 * hex colours alongside the var()) live in the SVG markup itself, so a
 * stylesheet failure still leaves a legible black-on-white diagram.
 *
 * The flow-active override below: while the flow-engine particle layer
 * is running on an SVG, drop the dashed-return stroke pattern.
 * Direction-of-motion alone distinguishes supply from return at that
 * point, and the stationary dash pattern visually competes with the
 * moving particles. flow-active is added by flow-engine.js only after
 * its reduced-motion bail-out, so reduced-motion keeps the dashes;
 * @media screen scopes the override so a printout still gets the
 * dashed encoding even if the page was animating on screen. Selector
 * intentionally targets any element type (paths and lines both carry
 * data-flow). The .edu-legend return swatch mirrors this: solid by
 * default (matching the animated diagram), dashed again under
 * @media print / prefers-reduced-motion, so the key always agrees
 * with what that visitor actually sees. Page-specific structural
 * diagrams without supply/return (e.g. the VFDs block diagram) stay
 * separate from this family — see vfds.html for the .vfd-svg precedent.
 * ────────────────────────────────────────────────────────────────────── */
.edu-svg {
    display: block;
    width: 100%;
    height: auto;
    margin: 1.5rem 0;
}
.edu-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem 1.5rem;
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin: -0.5rem 0 0;
    padding-left: 0.25rem;
}
.edu-legend .sw { display: inline-block; width: 26px; height: 0; vertical-align: middle; margin-right: 0.4rem; }
.edu-legend .sw.supply { border-top: 3px solid var(--blue); }
.edu-legend .sw.return { border-top: 3px solid var(--blue-cool); }

@media screen {
    svg.flow-active [data-flow="return"] {
        stroke-dasharray: none;
    }
}

@media print, (prefers-reduced-motion: reduce) {
    .edu-legend .sw.return { border-top-style: dashed; }
}

/* ──────────────────────────────────────────────────────────────────────
   WIDGET CHROME — shared "interactive panel" vocabulary used by the
   five widget pages: pump-control (×2 widgets), balancing, vfds,
   vfd-mock, hydronic-loops (d3 twin-T injection-pump widget).

   The widget shell is the recessed --surface-3 panel + the standard
   bits inside it: a "Try this:" prompt-link row, mono caps section
   labels, slider with label/value head, blue-readout pairs, the
   anecdote callout (with min-height to reserve space so reveals
   don't reflow the page below), and the 5-blade fan icon shared
   between the pump-control and vfds widgets. Page-specific
   INTERNALS (LCD, keypad, branch states, valve pills, temperature
   swatches, pump-curve canvas) stay in each page's {% block head %}
   since only that page uses them.

   Default anecdote left rule is --blue (the "extreme-state reward"
   variant on pump-control / vfds / hydronic-loops). The .warn
   modifier flips it to --red for failure callouts (balancing).
*/

.widget {
    margin-top: 1.25rem;
    padding: 1.1rem 1.25rem;
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 3px;
}

.widget-try {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    margin-bottom: 0.85rem;
    line-height: 1.7;
}
.widget-try .lbl { letter-spacing: 0.05em; text-transform: uppercase; margin-right: 0.6rem; }
.widget-try a {
    color: var(--accent);
    text-decoration: none;
    margin-right: 0.85rem;
    cursor: pointer;
    border-bottom: 1px dashed var(--accent-dim);
}
.widget-try a:hover { color: var(--text-bright); border-bottom-color: var(--accent); }

.widget-section-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    color: var(--text-dim);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin-bottom: 0.5rem;
}

.widget-slider-head {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    font-family: var(--mono);
    font-size: 0.72rem;
    color: var(--text-dim);
    margin-bottom: 0.1rem;
}
.widget-slider-head .v {
    color: var(--blue);
    font-weight: 600;
    font-size: 0.95rem;
}
.widget-slider { width: 100%; margin: 0.15rem 0 0.4rem; }

.widget-readout-label {
    font-family: var(--mono);
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-dim);
    margin-bottom: 0.15rem;
}
.widget-readout-value {
    font-family: var(--mono);
    font-size: 1.0rem;
    font-weight: 600;
    color: var(--blue);
    line-height: 1.15;
    font-variant-numeric: tabular-nums;
}
.widget-readout-value .unit {
    font-size: 0.65em;
    color: var(--text-dim);
    font-weight: 500;
    margin-left: 0.2rem;
}

.widget-anecdote-wrap { min-height: 1.5rem; margin-top: 0.6rem; }
.widget-anecdote {
    background: var(--bg);
    border: 1px solid var(--border);
    border-left: 4px solid var(--blue);
    border-radius: 3px;
    padding: 0.75rem 1rem;
    font-size: 0.86rem;
    line-height: 1.7;
    color: var(--text);
}
.widget-anecdote strong { color: var(--text-bright); font-weight: 600; }
.widget-anecdote.warn { border-left-color: var(--red); }

/* ── FAILURE-STATE CALLOUT — sits below a .ps-row result when the input
   branch is invalid (result-value goes muted '—', this callout names
   the failure mode AND the action). Sibling to .widget-anecdote (same
   shell shape, different domain: tool outputs, not education widgets).
   Warm-orange left rule matches the in-use failure-warning hue on
   economizer-ratio's .er-feas.warn pill. ── */
.failure-callout {
    margin-top: 0.6rem;
    padding: 0.75rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-left: 4px solid var(--heat);
    border-radius: 3px;
    font-size: 0.86rem;
    line-height: 1.7;
    color: var(--text);
}
.failure-callout strong { color: var(--text-bright); font-weight: 600; }

/* 5-blade fan icon — visual handle for "the drive is energising
   something." Used by the run/speed widget on vfds and both
   pump-control widgets. The SVG markup (center + 4 ellipses at
   72°/144°/216°/288° around 50,50) lives inline on each page; the
   per-frame rAF loop writes a rotate transform onto the .widget-
   fan-blades group. Pages add their own positioning/sizing
   alongside (e.g. .vfd-w-status-row .widget-fan or .pc-w-fan-wrap
   .widget-fan).

   Reduced-motion: the JS engine short-circuits when the OS pref
   is set, leaving blade angle at 0. The colour swap below still
   communicates running vs stopped. The !important override on
   .widget-fan-blades is belt-and-braces against a stale transform
   attribute lingering on the group. */
.widget-fan ellipse {
    fill: var(--blue-cool);
    transition: fill 0.25s;
}
.widget-fan.spinning ellipse {
    fill: var(--blue);
}

/* ──────────────────────────────────────────────────────────────────────
 * BAS FLARE — "BAS-instrument quiet" widget polish.
 *
 * Subtle panel-instrument hooks reused across widgets:
 *   .bas-led / .bas-led.active / .bas-led.fault — 6px round status
 *     dot. Neutral by default; .active gets the accent fill + a soft
 *     pulsing ring; .fault swaps to --red and pulses faster. aria-
 *     hidden in pages since the adjacent text-state already conveys
 *     status to screen readers.
 *   .lcd-scanline — overlay class on an LCD-style panel. Adds a
 *     near-invisible horizontal scanline pattern via ::after; pure
 *     visual texture, no motion.
 *   .lcd-flicker — one-shot 150ms opacity dip; JS adds the class
 *     then removes it on a setTimeout to trigger the dip on every
 *     LCD value update.
 *   .bas-state-flash — one-shot 350ms outer accent-glow ring around
 *     a row/card. JS adds the class on a state transition and
 *     removes it on a setTimeout.
 *   .bas-breathe — slow box-shadow breathing ring; used by the
 *     psychrometric chart's state-point chip.
 *
 * Reduced motion: the global @media (prefers-reduced-motion: reduce)
 * block below already disables all keyframe animations site-wide, so
 * these rules don't need their own guard. LEDs still color-code state
 * — only the pulse goes quiet.
 * ────────────────────────────────────────────────────────────────────── */
.bas-led {
    display: inline-block;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--text-dim);
    border: 1px solid var(--border);
    vertical-align: middle;
    flex-shrink: 0;
}
.bas-led.active {
    background: var(--accent);
    border-color: var(--accent-glow);
    box-shadow: 0 0 0 2px var(--accent-soft);
    animation: bas-led-pulse 2s ease-in-out infinite;
}
.bas-led.fault {
    background: var(--red);
    border-color: rgba(196,56,47,0.32);
    box-shadow: 0 0 0 2px rgba(196,56,47,0.08);
    animation: bas-led-pulse 1.2s ease-in-out infinite;
}
.bas-led.warn {
    background: var(--heat);
    border-color: rgba(200,120,42,0.32);
    box-shadow: 0 0 0 2px rgba(200,120,42,0.08);
    animation: bas-led-pulse 1.6s ease-in-out infinite;
}
@keyframes bas-led-pulse {
    0%, 100% { opacity: 1; }
    50%      { opacity: 0.55; }
}

.lcd-scanline { position: relative; }
.lcd-scanline::after {
    content: "";
    position: absolute;
    inset: 0;
    pointer-events: none;
    background: repeating-linear-gradient(
        0deg,
        transparent 0,
        transparent 2px,
        rgba(29,37,31,0.045) 2px,
        rgba(29,37,31,0.045) 3px
    );
    border-radius: inherit;
}
@keyframes lcd-flicker {
    0%   { opacity: 1; }
    45%  { opacity: 0.68; }
    100% { opacity: 1; }
}
.lcd-flicker { animation: lcd-flicker 150ms ease-in-out 1; }

@keyframes bas-state-flash {
    0%   { box-shadow: 0 0 0 2px var(--accent-glow), 0 0 0 4px var(--accent-soft); }
    100% { box-shadow: 0 0 0 2px transparent,        0 0 0 4px transparent; }
}
.bas-state-flash { animation: bas-state-flash 350ms ease-out 1; }

@keyframes bas-breathe {
    0%, 100% { box-shadow: 0 0 0 6px rgba(67,136,28,0.16); }
    50%      { box-shadow: 0 0 0 11px rgba(67,136,28,0.05); }
}
.bas-breathe { animation: bas-breathe 1.8s ease-in-out infinite; }

/* Utility: hide an element that JS toggles into view. display:none
   drops it from layout and the accessibility tree. Placed after the
   component rules so it wins the specificity tie against a
   single-class display rule (e.g. .result-panel's display:flex). */
.hidden { display: none; }

@media (prefers-reduced-motion: reduce) {
    .widget-fan-blades { transform: none !important; }
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}