/* ──────────────────────────────────────────────────────────────────────
 * 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);
    --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 */
    --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: var(--bg);
    color: var(--text);
    font-family: var(--sans);
    font-size: 16px;
    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;
}
main { flex: 1; }

/* ── 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); }
.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: 0.68rem;
    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 ── */
.hero {
    position: relative;
    z-index: 1;
    padding: 5rem 2rem 4rem;
    max-width: 880px;
    margin: 0 auto;
    width: 100%;   /* don't shrink-to-fit inside body's flex column */
    animation: fadeUp 0.5s ease both;
}

.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;
    gap: 0.6rem;
}
.hero-eyebrow::before {
    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-bottom: 2rem;
    line-height: 1.8;
}

.hero-badges { display: flex; flex-wrap: wrap; 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: 880px;
    margin: 0 auto;
    padding: 2.5rem 2rem 4rem;
    width: 100%;
}
.hero + main { padding-top: 0; }

.section-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.section-label {
    font-family: var(--mono);
    font-size: 0.82rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--accent);
    white-space: nowrap;
    margin: 0;
}
.section-line { flex: 1; height: 1px; background: var(--border); }

/* ── TOOL CARD ── */
.tool-card {
    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. Wider line-height and a constrained max-width
   keep the intro readable at narrative-length. 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);
    max-width: 660px;
    margin-bottom: 1.75rem;
}

/* ── 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: 0.66rem;
    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: 0.65rem;
    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;
    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: 0.63rem;
    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: 0.68rem;
    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: 0.6rem;
    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;
}

/* ── FOOTER ── */
footer {
    position: relative;
    z-index: 1;
    border-top: 1px solid var(--border);
    padding: 1.5rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 880px;
    margin: 0 auto;
    width: 100%;   /* don't shrink-to-fit inside body's flex column */
}
.footer-text {
    font-family: var(--mono);
    font-size: 0.68rem;
    color: var(--text-dim);
}

/* ── ANIMATIONS ── */
@keyframes fadeUp {
    from { opacity: 0; transform: translateY(14px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ── 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; }
    .hero, main      { padding-left: 1rem; padding-right: 1rem; }
    footer           { padding: 1.25rem 1rem; flex-direction: column; gap: 0.4rem; }
    /* 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: 0.62rem;
    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); }

/* ── SUBHEAD (within a tool body) ── */
.subhead {
    font-family: var(--mono);
    font-size: 0.66rem;
    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: 0.6rem;
    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,
.nav-card:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}
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);
}

/* 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: 0.64rem;
    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: 0.62rem;
    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; }
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)); }

.nav-card {
    display: block;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 1.3rem 1.4rem;
    text-decoration: none;
    color: inherit;
    transition: border-color 0.18s, transform 0.18s;
}
.nav-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.nav-card-tag {
    display: inline-block;
    font-family: var(--mono);
    font-size: 0.6rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--accent);
    background: var(--accent-dim);
    border: 1px solid var(--accent-glow);
    border-radius: 2px;
    padding: 0.13rem 0.45rem;
    margin-bottom: 0.7rem;
}
.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(--accent); }
.nav-card-desc {
    font-size: 0.85rem;
    color: var(--text-dim);
    line-height: 1.6;
}

/* ──────────────────────────────────────────────────────────────────────
 * 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); }

/* ──────────────────────────────────────────────────────────────────────
 * 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);
}
/* 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 three columns to a single stack
   (Input → Output → Reference). The "two products, one codebase" plan
   eventually wants a purpose-built mobile experience for this tool; this
   is just the conservative first pass.
   // mobile-first treatment of this tool is a future task — see site-ideas-and-friction.md */
@media (max-width: 900px) {
    .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; }
    .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: 0.66rem;
    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: 0.62rem;
    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: 0.6rem;
    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;
}
.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); }

/* 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);
}

/* 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;
    }
}