:root{color-scheme:light;box-sizing:border-box;padding-top:env(safe-area-inset-top,0px);padding-bottom:env(safe-area-inset-bottom,0px)}html{scroll-padding-top:env(safe-area-inset-top,0px)}body{margin:0;padding:0;font:14px -apple-system,BlinkMacSystemFont,sans-serif;background:#fff;color:#000}img{max-width:100%}[hidden]:not([hidden=until-found i]){display:none!important}

/* Layout concept: an engineering data sheet. Hairline rules, a title block top right, the equation on a ruled panel,
   inputs beside a sticky readout. Blue is the one accent; type is DIN-like condensed for labels, Barlow for reading, Plex Mono for numbers. */
:root {
  --bg: #eceff2; --surface: #fafbfc; --raise: #ffffff;
  --ink: #0e1620; --ink2: #46515e; --muted: #5d6976;
  --rule: #cfd6dd; --rule2: #e1e6ea;
  --accent: #2a78d6; --accent-ink: #1c5cab; --accent-wash: rgba(42,120,214,.10); --on-accent: #ffffff;
  --good: #006300; --bad: #b32d2d; --good-wash: rgba(0,99,0,.08); --bad-wash: rgba(179,45,45,.08);
  --f-display: "Barlow Condensed", "Arial Narrow", system-ui, sans-serif;
  --f-body: "Barlow", system-ui, -apple-system, "Segoe UI", sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --f-math: "STIX Two Math", "Cambria Math", "Latin Modern Math", "Times New Roman", serif;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0d1218; --surface: #141a21; --raise: #19212a;
    --ink: #e7ecf1; --ink2: #aab5c1; --muted: #8f9aa6;
    --rule: #2a343f; --rule2: #202a33;
    --accent: #3987e5; --accent-ink: #86b6ef; --accent-wash: rgba(57,135,229,.16); --on-accent: #08111c;
    --good: #0ca30c; --bad: #e66767; --good-wash: rgba(12,163,12,.14); --bad-wash: rgba(230,103,103,.14);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0d1218; --surface: #141a21; --raise: #19212a;
  --ink: #e7ecf1; --ink2: #aab5c1; --muted: #8f9aa6;
  --rule: #2a343f; --rule2: #202a33;
  --accent: #3987e5; --accent-ink: #86b6ef; --accent-wash: rgba(57,135,229,.16); --on-accent: #08111c;
  --good: #0ca30c; --bad: #e66767; --good-wash: rgba(12,163,12,.14); --bad-wash: rgba(230,103,103,.14);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  background: var(--bg); color: var(--ink);
  font: 400 16px/1.55 var(--f-body);
  padding-left: max(16px, env(safe-area-inset-left, 0px));
  padding-right: max(16px, env(safe-area-inset-right, 0px));
  padding-block: 0;
}
body::before { content: ""; position: fixed; inset: 0 0 auto; height: env(safe-area-inset-top, 0px); z-index: 10; background: var(--bg); }
.wrap { max-width: 1120px; margin: 0 auto; }
a { color: var(--accent-ink); text-underline-offset: 2px; }
sub, sup { line-height: 0; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
button, select, input { font: inherit; color: inherit; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------- top bar ---------- */
.top { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding: 14px 0; border-bottom: 1px solid var(--rule); }
.brand { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); }
.brand svg { width: 26px; height: 26px; flex: none; }
.brand span { font: 700 19px/1 var(--f-display); letter-spacing: .09em; text-transform: uppercase; }
.nav { display: flex; gap: 4px; }
.nav a { font: 600 14px/1 var(--f-display); letter-spacing: .09em; text-transform: uppercase; text-decoration: none; color: var(--ink2); padding: 11px 12px; border-radius: 3px; }
.nav a:hover { background: var(--accent-wash); color: var(--ink); }
.nav a[aria-current="page"] { color: var(--ink); box-shadow: inset 0 -2px 0 var(--accent); border-radius: 0; }
main { padding-block: 28px 56px; min-height: 60vh; }

/* ---------- type ---------- */
.eyebrow { font: 600 13px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin: 0 0 10px; }
h1 { font: 600 clamp(2rem, 5.2vw, 3.3rem)/1.04 var(--f-display); letter-spacing: -.005em; margin: 0 0 14px; text-wrap: balance; }
h2.h { font: 600 13px/1 var(--f-display); letter-spacing: .14em; text-transform: uppercase; color: var(--muted); margin: 0 0 14px; padding-top: 4px; }
.lede { font-size: 1.08rem; color: var(--ink2); max-width: 62ch; margin: 0; }
.sub { color: var(--ink2); font-size: .94rem; margin: -4px 0 14px; max-width: 70ch; }
.sec { margin-top: 44px; }
.mono { font-family: var(--f-mono); }

/* ---------- home ---------- */
.hero { padding-top: 12px; }
.hero h1 { max-width: 24ch; }
.search { position: relative; margin-top: 26px; max-width: 760px; }
.search input { width: 100%; height: 56px; padding: 0 56px 0 50px; border: 1px solid var(--ink2); border-radius: 4px; background: var(--raise); font-size: 1.08rem; }
.search svg { position: absolute; left: 16px; top: 17px; width: 22px; height: 22px; color: var(--muted); pointer-events: none; }
.search kbd { position: absolute; right: 14px; top: 15px; font: 500 13px/1 var(--f-mono); color: var(--muted); border: 1px solid var(--rule); border-radius: 3px; padding: 5px 8px; background: var(--surface); }
.searchrow { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; max-width: 1000px; }
.searchrow .search { margin-top: 0; flex: 1 1 380px; max-width: none; }
.searchrow select { height: 56px; flex: 1 1 200px; max-width: 280px; border-color: var(--ink2); border-radius: 4px; font-size: 1rem; padding-left: 14px; }
#pfsel { min-width: min(100%, 340px); max-width: 100%; }
#secsel, #fieldsel { min-width: 0; }
#fieldsel { max-width: 380px; }
@media (max-width: 640px) { .searchrow select { flex: 1 1 100%; max-width: 100%; width: 100%; } }
#fieldsel:disabled { opacity: .55; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
.chip { cursor: pointer; font: 600 14px/1 var(--f-display); letter-spacing: .08em; text-transform: uppercase; padding: 0 13px; min-height: 38px; border: 1px solid var(--rule); border-radius: 3px; background: var(--raise); color: var(--ink2); display: inline-flex; align-items: center; gap: 7px; }
.chip:hover { border-color: var(--ink2); color: var(--ink); }
.chip[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.chip .sym { font-size: 1rem; letter-spacing: 0; text-transform: none; }
.count { font: 500 13px var(--f-mono); color: var(--muted); margin: 26px 0 8px; }
.list { border-top: 1px solid var(--ink2); }
.list:empty { border-top: 0; }
.row { display: grid; grid-template-columns: 84px minmax(0, 1fr) minmax(0, 220px); gap: 6px 20px; align-items: baseline; padding: 18px 10px; border-bottom: 1px solid var(--rule); text-decoration: none; color: inherit; }
.row:hover { background: var(--accent-wash); }
.row .ref { font: 500 13px var(--f-mono); color: var(--muted); }
.row strong { font: 600 1.3rem/1.2 var(--f-display); letter-spacing: .005em; display: block; color: var(--ink); }
.row .s { color: var(--ink2); font-size: .95rem; display: block; margin-top: 2px; }
.row .vars { display: flex; flex-wrap: wrap; gap: 4px 10px; margin-top: 8px; color: var(--muted); font-size: .92rem; }
.row .fld { font: 600 13px/1.2 var(--f-display); letter-spacing: .1em; text-transform: uppercase; color: var(--ink2); text-align: right; }
.row .fld i { display: block; font: normal 400 13px var(--f-mono); letter-spacing: 0; text-transform: none; color: var(--muted); margin-top: 4px; }
.empty { padding: 28px 10px; color: var(--ink2); border-bottom: 1px solid var(--rule); }
.note { margin-top: 40px; color: var(--muted); font-size: .9rem; max-width: 70ch; }
.sym { font-family: var(--f-math); font-style: italic; }

/* ---------- formula sheet ---------- */
.crumbs { font: 500 13px var(--f-mono); color: var(--muted); margin-bottom: 18px; }
.crumbs a { color: var(--muted); }
.sheethead { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 20px 40px; align-items: start; }
.tblock { margin: 0; border: 1px solid var(--ink2); display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); min-width: 300px; background: var(--surface); }
.tblock div { padding: 8px 12px 9px; border-right: 1px solid var(--rule); border-bottom: 1px solid var(--rule); }
.tblock div:nth-child(2n) { border-right: 0; }
.tblock div:nth-last-child(-n+2) { border-bottom: 0; }
.tblock dt { font: 600 11px/1 var(--f-display); letter-spacing: .14em; text-transform: uppercase; color: var(--muted); margin-bottom: 5px; }
.tblock dd { margin: 0; font: 500 13px/1.3 var(--f-mono); }
.eqpanel { margin-top: 28px; background: var(--surface); border: 1px solid var(--rule); padding: 30px 24px 22px; }
.eqbox { overflow-x: auto; text-align: center; padding-block: 4px; }
math { font-family: var(--f-math); font-size: clamp(1.45rem, 3.6vw, 2.1rem); color: var(--ink); }
math + math { margin-top: 12px; }
.eqnote { text-align: center; color: var(--ink2); font-size: .94rem; margin: 10px auto 0; max-width: 70ch; }
.plain { margin: 20px auto 0; padding-top: 18px; border-top: 1px solid var(--rule2); max-width: 70ch; color: var(--ink); font-size: 1.02rem; }

.solvebar { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin-bottom: 14px; }
.solvebar .lab { font: 600 13px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin-right: 6px; }
.calcgrid { display: grid; grid-template-columns: minmax(0, 1fr) 330px; gap: 24px; align-items: start; }
.inputs { background: var(--surface); border: 1px solid var(--rule); }
.vrow { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 8px 14px; align-items: center; padding: 14px 16px 10px; border-bottom: 1px solid var(--rule2); }
.vrow:last-child { border-bottom: 0; }
.vrow.is-unknown { background: var(--accent-wash); }
.vlab { display: flex; align-items: baseline; gap: 10px; min-width: 0; flex-wrap: wrap; }
.vlab .sym { font-size: 1.2rem; min-width: 2.2ch; }
.vlab .vn { font-size: .95rem; color: var(--ink2); }
.tag { font: 600 11px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; padding: 4px 6px; border-radius: 2px; background: var(--accent); color: var(--on-accent); }
.warn { font-size: .82rem; color: var(--bad); }
.vctl { display: flex; align-items: center; gap: 8px; justify-self: end; }
.num { width: 9.2rem; height: 40px; padding: 0 10px; text-align: right; border: 1px solid var(--rule); border-radius: 3px; background: var(--raise); font: 500 15px var(--f-mono); }
.num:hover { border-color: var(--ink2); }
.num[readonly] { background: transparent; border-color: var(--accent); color: var(--ink); }
.num[aria-invalid="true"] { border-color: var(--bad); }
.unit { font: 400 13px var(--f-mono); color: var(--muted); min-width: 3.2ch; max-width: 11ch; line-height: 1.2; }
.rgwrap { grid-column: 1 / -1; }
.rg { -webkit-appearance: none; appearance: none; width: 100%; height: 26px; background: transparent; margin: 0; --p: 50%; cursor: pointer; }
.rg:disabled { opacity: .35; cursor: default; }
.rg::-webkit-slider-runnable-track { height: 2px; background: linear-gradient(to right, var(--accent) var(--p), var(--rule) var(--p)); }
.rg::-moz-range-track { height: 2px; background: var(--rule); }
.rg::-moz-range-progress { height: 2px; background: var(--accent); }
.rg::-webkit-slider-thumb { -webkit-appearance: none; box-sizing: border-box; width: 18px; height: 18px; margin-top: -8px; border-radius: 50%; background: var(--accent); border: 2px solid var(--surface); box-shadow: 0 0 0 1px var(--accent); }
.rg::-moz-range-thumb { box-sizing: border-box; width: 18px; height: 18px; border-radius: 50%; background: var(--accent); border: 2px solid var(--surface); box-shadow: 0 0 0 1px var(--accent); }
.rgmeta { display: flex; justify-content: space-between; font: 400 11px var(--f-mono); color: var(--muted); margin-top: -2px; }

.result { position: sticky; top: calc(env(safe-area-inset-top, 0px) + 12px); background: var(--raise); border: 1px solid var(--ink2); padding: 18px 18px 14px; }
.rlab { font: 600 12px/1.3 var(--f-display); letter-spacing: .13em; text-transform: uppercase; color: var(--muted); margin: 0 0 8px; }
.rlab .sym { font-size: 1.05rem; letter-spacing: 0; text-transform: none; color: var(--ink); }
.rval { display: flex; align-items: baseline; gap: 8px; flex-wrap: wrap; margin: 0; }
.rval output { font: 500 clamp(2.2rem, 4vw, 2.9rem)/1.05 var(--f-mono); letter-spacing: -.02em; word-break: break-all; }
.rval .u { font: 400 15px var(--f-mono); color: var(--ink2); }
.rmsg { margin: 8px 0 0; font-size: .9rem; color: var(--bad); }
.derived { list-style: none; margin: 14px 0 0; padding: 10px 0 0; border-top: 1px solid var(--rule); }
.derived li { display: flex; justify-content: space-between; gap: 12px; padding: 5px 0; font-size: .9rem; color: var(--ink2); }
.derived b { font: 500 13px var(--f-mono); color: var(--ink); text-align: right; font-weight: 500; }
.derived-m { display: none; }
.consts { margin: 10px 0 0; font: 400 12px var(--f-mono); color: var(--muted); }

/* ---------- charts ---------- */
.chartbox { background: var(--surface); border: 1px solid var(--rule); padding: 18px 18px 12px; }
.cap { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 6px 16px; font-size: .9rem; color: var(--ink2); margin-bottom: 8px; }
.cap b { font: 500 13px var(--f-mono); color: var(--ink); font-weight: 500; }
.key { display: inline-flex; align-items: center; gap: 7px; }
.key i { display: inline-block; width: 1px; height: 14px; background: var(--ink2); }
.torn { --lw: 160px; position: relative; }
.tr { display: grid; grid-template-columns: var(--lw) minmax(0, 1fr); gap: 12px; align-items: center; border-bottom: 1px solid var(--rule2); padding: 2px 0; }
.tr:focus-visible { outline: 2px solid var(--accent); outline-offset: -2px; }
.tr .lab { display: flex; flex-direction: column; line-height: 1.2; min-width: 0; }
.tr .lab .sym { font-size: 1.1rem; }
.tr .lab small { font-size: .78rem; color: var(--muted); }
.tr .lab .kd { align-self: flex-start; margin-top: 3px; font: 600 10px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; color: var(--accent-ink); }
.track { position: relative; height: 38px; }
.track .gl { position: absolute; top: 0; bottom: 0; width: 1px; background: var(--rule2); }
.track .bl { position: absolute; top: 0; bottom: 0; width: 1px; background: var(--ink2); }
.bar { position: absolute; top: 11px; height: 16px; background: var(--accent); }
.bar.lo { border-radius: 4px 0 0 4px; }
.bar.hi { border-radius: 0 4px 4px 0; }
.tr:hover .bar, .tr:focus-visible .bar { filter: brightness(1.12); }
.vl { position: absolute; top: 50%; transform: translateY(-50%); font: 400 11px/1 var(--f-mono); color: var(--ink2); white-space: nowrap; }
.axis { position: relative; height: 22px; margin-left: calc(var(--lw) + 12px); }
.axis span { position: absolute; top: 5px; transform: translateX(-50%); font: 400 11px/1 var(--f-mono); color: var(--muted); }
.insights { margin: 18px 0 0; padding: 0; list-style: none; display: grid; gap: 10px; max-width: 78ch; }
.insights li { padding-left: 18px; position: relative; color: var(--ink); }
.insights li::before { content: ""; position: absolute; left: 0; top: .62em; width: 8px; height: 1px; background: var(--ink2); }
.sweephead { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 14px; margin-bottom: 10px; }
.sweephead label { font: 600 13px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
select { height: 40px; padding: 0 34px 0 12px; border: 1px solid var(--rule); border-radius: 3px; background-color: var(--raise); }
svg.plot { display: block; width: 100%; height: auto; overflow: visible; touch-action: pan-y; }
svg.plot text { font: 400 11px var(--f-mono); fill: var(--muted); }
svg.plot .ttl { fill: var(--ink2); font: 400 12px var(--f-body); }
svg.plot .nowl { fill: var(--ink); font: 500 11px var(--f-mono); }
.grid line { stroke: var(--rule2); stroke-width: 1; }
.axisline { stroke: var(--rule); stroke-width: 1; }
.curve { fill: none; stroke: var(--accent); stroke-width: 2; stroke-linejoin: round; stroke-linecap: round; }
.area { fill: var(--accent); opacity: .10; }
.nowdot { fill: var(--accent); stroke: var(--surface); stroke-width: 2; }
.xh line { stroke: var(--ink2); stroke-width: 1; }
.xh circle { fill: var(--accent); stroke: var(--surface); stroke-width: 2; }
details.data { margin-top: 14px; }
details.data summary { cursor: pointer; font: 600 13px/1 var(--f-display); letter-spacing: .12em; text-transform: uppercase; color: var(--accent-ink); padding: 10px 0; }
.tbl { overflow-x: auto; margin-top: 8px; }
table { border-collapse: collapse; width: 100%; font-size: .9rem; }
th { font: 600 12px/1.2 var(--f-display); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); text-align: left; padding: 8px 12px 8px 0; border-bottom: 1px solid var(--ink2); white-space: nowrap; }
td { padding: 8px 12px 8px 0; border-bottom: 1px solid var(--rule2); font-variant-numeric: tabular-nums; vertical-align: baseline; }
td.n { font-family: var(--f-mono); font-size: .85rem; white-space: nowrap; }
.tbl h3 { font: 600 14px var(--f-display); letter-spacing: .1em; text-transform: uppercase; margin: 22px 0 4px; color: var(--ink2); }

.varlist { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 0 32px; }
.v { padding: 14px 0; border-bottom: 1px solid var(--rule); display: grid; grid-template-columns: 56px minmax(0, 1fr); gap: 2px 12px; }
.v .sym { font-size: 1.45rem; grid-row: span 3; line-height: 1.1; }
.v h3 { margin: 0; font: 600 1.05rem/1.2 var(--f-display); letter-spacing: .02em; }
.v .meta { font: 400 12px var(--f-mono); color: var(--muted); }
.v p { margin: 2px 0 0; color: var(--ink2); font-size: .94rem; }
.worked { margin: 0; padding: 0; list-style: none; counter-reset: s; display: grid; gap: 10px; max-width: 80ch; }
.worked li { counter-increment: s; padding-left: 38px; position: relative; }
.worked li::before { content: counter(s); position: absolute; left: 0; top: 1px; width: 24px; height: 24px; border: 1px solid var(--ink2); text-align: center; font: 500 12px/22px var(--f-mono); border-radius: 50%; }
.worked b { font-family: var(--f-mono); font-weight: 500; }
.cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 28px 40px; }
.cols h2.h { margin-bottom: 10px; }
.cols ul { margin: 0; padding: 0; list-style: none; display: grid; gap: 8px; }
.cols li { padding-left: 16px; position: relative; font-size: .96rem; color: var(--ink2); }
.cols li::before { content: ""; position: absolute; left: 0; top: .66em; width: 7px; height: 1px; background: var(--ink2); }
.stat { background: var(--surface); border: 1px solid var(--rule); padding: 16px 18px; max-width: 78ch; color: var(--ink2); }
.pre li b { font-weight: 600; color: var(--ink); }
.related { display: flex; flex-wrap: wrap; gap: 10px; }
.related a { text-decoration: none; border: 1px solid var(--rule); padding: 10px 14px; border-radius: 3px; background: var(--raise); color: var(--ink); font-weight: 500; }
.related a:hover { border-color: var(--accent); }
.related a small { display: block; font: 400 12px var(--f-mono); color: var(--muted); }

/* ---------- practice ---------- */
.prac { max-width: 820px; }
.group-lab { font: 600 12px/1 var(--f-display); letter-spacing: .13em; text-transform: uppercase; color: var(--muted); margin: 22px 0 8px; }
.problem { margin-top: 24px; background: var(--surface); border: 1px solid var(--ink2); padding: 22px 22px 20px; }
.problem h2 { font: 600 1.35rem/1.2 var(--f-display); margin: 0 0 4px; }
.given { list-style: none; padding: 0; margin: 14px 0 16px; display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 4px 24px; }
.given li { display: flex; justify-content: space-between; gap: 10px; padding: 6px 0; border-bottom: 1px solid var(--rule2); }
.given li span:first-child { color: var(--ink2); }
.given b { font: 500 14px var(--f-mono); }
.find { font-size: 1.02rem; margin: 0 0 14px; }
.ans { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.btn { cursor: pointer; font: 600 14px/1 var(--f-display); letter-spacing: .1em; text-transform: uppercase; min-height: 40px; padding: 0 16px; border: 1px solid var(--ink2); background: var(--raise); border-radius: 3px; }
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.btn.primary:hover { filter: brightness(1.08); }
.btns { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }
.fb { margin-top: 16px; padding: 12px 14px; border: 1px solid; display: flex; gap: 12px; align-items: flex-start; }
.fb.good { color: var(--good); border-color: var(--good); background: var(--good-wash); }
.fb.bad { color: var(--bad); border-color: var(--bad); background: var(--bad-wash); }
.fb svg { width: 20px; height: 20px; flex: none; margin-top: 2px; }
.fb div { color: var(--ink); }
.fb strong { font: 600 15px var(--f-display); letter-spacing: .1em; text-transform: uppercase; display: block; }
.hint, .sol { margin-top: 14px; padding: 12px 14px; background: var(--accent-wash); font-size: .96rem; }
.sol .worked { margin-top: 8px; }
.score { margin-top: 18px; font: 500 13px var(--f-mono); color: var(--muted); }

/* ---------- tooltip ---------- */
.tip { position: fixed; z-index: 30; pointer-events: none; background: var(--raise); border: 1px solid var(--rule); box-shadow: 0 6px 22px rgba(8,16,28,.18); padding: 8px 11px; border-radius: 3px; max-width: min(300px, calc(100vw - 24px)); font-size: 13px; line-height: 1.4; color: var(--ink2); }
.tip b { display: block; font: 500 14px var(--f-mono); color: var(--ink); margin-bottom: 2px; }
.tip[hidden] { display: none; }

footer .legal-links { display: flex; flex-wrap: wrap; gap: 6px 18px; margin-top: 12px; font-size: .86rem; }
footer .legal-links a { color: inherit; text-decoration: underline; text-underline-offset: 2px; }
.legal { max-width: 68ch; padding-bottom: 24px; }
.legal h2 { font: 600 1.15rem/1.3 var(--f-display); margin: 28px 0 8px; }
.legal p, .legal li { line-height: 1.6; }
.legal ul { padding-left: 1.2em; }
.legal-date { color: var(--muted); font-size: .88rem; margin-top: 28px; }
footer { border-top: 1px solid var(--rule); padding-block: 18px max(30px, env(safe-area-inset-bottom, 0px)); color: var(--muted); font-size: .88rem; }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .calcgrid { grid-template-columns: minmax(0, 1fr); }
  .result { order: -1; padding: 12px 14px 10px; z-index: 5; }
  .result .derived, .result .consts { display: none; }
  .rval output { font-size: 2rem; }
  .derived-m { display: block; padding: 4px 16px 12px; border-top: 1px solid var(--rule2); }
  .derived-m .derived { margin: 0; padding: 0; border: 0; }
  .sheethead { grid-template-columns: minmax(0, 1fr); }
  .tblock { min-width: 0; max-width: 420px; }
}
@media (max-width: 640px) {
  .row { grid-template-columns: minmax(0, 1fr); gap: 4px; }
  .row .fld { text-align: left; }
  .row .fld i { display: inline; margin-left: 8px; }
  .eqpanel { padding: 22px 14px 18px; }
  .torn { --lw: 0px; }
  .tr { grid-template-columns: minmax(0, 1fr); gap: 0; padding-top: 8px; }
  .tr .lab { flex-direction: row; align-items: baseline; gap: 8px; flex-wrap: wrap; }
  .tr .lab .kd { margin-top: 0; }
  .axis { margin-left: 0; }
  .vrow { padding-inline: 12px; }
  .chartbox { padding-inline: 12px; }
}
@media (prefers-reduced-motion: no-preference) {
  .row, .chip, .btn, .nav a { transition: background-color .12s, border-color .12s, color .12s; }
}
@media (max-width: 480px) { math { font-size: 1.12rem; } }
select { max-width: 100%; }