/* Engineering Calc Tools
   Layout: a drawing sheet. Content column plus a narrow right rail (ads, related tools)
   on tool pages; each calculator sits on a green engineering computation pad with a
   faint grid, headed by a drawing-style title block. Dark theme becomes a blueprint. */

@font-face { font-family: "Barlow Semi Condensed"; font-weight: 600; font-style: normal; font-display: swap; src: url("../fonts/barlow-semi-condensed-latin-600-normal.woff2") format("woff2"); }
@font-face { font-family: "Barlow Semi Condensed"; font-weight: 700; font-style: normal; font-display: swap; src: url("../fonts/barlow-semi-condensed-latin-700-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 400; font-style: normal; font-display: swap; src: url("../fonts/ibm-plex-sans-latin-400-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 400; font-style: italic; font-display: swap; src: url("../fonts/ibm-plex-sans-latin-400-italic.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 500; font-style: normal; font-display: swap; src: url("../fonts/ibm-plex-sans-latin-500-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 600; font-style: normal; font-display: swap; src: url("../fonts/ibm-plex-sans-latin-600-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Mono"; font-weight: 400; font-style: normal; font-display: swap; src: url("../fonts/ibm-plex-mono-latin-400-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Mono"; font-weight: 500; font-style: normal; font-display: swap; src: url("../fonts/ibm-plex-mono-latin-500-normal.woff2") format("woff2"); }

:root {
  /* Color: computation-pad paper, graphite ink, drafting-blue ink, red pencil */
  --paper: #F6F8F3;
  --surface: #FFFFFF;
  --pad: #ECF2E7;
  --pad-line: #DAE5D3;
  --ink: #16201A;
  --ink-2: #485850;
  --ink-3: #5F6F65;
  --rule: #C8D4C3;
  --rule-strong: #93A68E;
  --accent: #1452A0;
  --accent-ink: #FFFFFF;
  --accent-soft: #E1EAF6;
  --mark: #B0281D;
  --mark-soft: #F7E3E0;
  --s3: #8A5F00;
  --warn-bg: #FFF3D1;
  --warn-fg: #5E4300;
  --warn-rule: #E2BC5E;
  --ok: #1E7039;

  /* Type: condensed signage display, plex body, plex mono for numbers */
  --f-display: "Barlow Semi Condensed", "Arial Narrow", "Roboto Condensed", system-ui, sans-serif;
  --f-body: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --t-xs: 0.75rem;
  --t-sm: 0.875rem;
  --t-base: 1.0625rem;
  --t-md: 1.25rem;
  --t-lg: 1.625rem;
  --t-xl: 2.25rem;
  --t-2xl: 3rem;

  --gutter-l: max(16px, env(safe-area-inset-left, 0px));
  --gutter-r: max(16px, env(safe-area-inset-right, 0px));
  --radius: 3px;
  --grid: 24px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #0D1928;
    --surface: #0A1421;
    --pad: #10223A;
    --pad-line: #19324F;
    --ink: #E3EBF4;
    --ink-2: #A8B9CC;
    --ink-3: #8DA1B8;
    --rule: #243E5E;
    --rule-strong: #3E5F86;
    --accent: #84BAFF;
    --accent-ink: #0B1626;
    --accent-soft: #15304F;
    --mark: #FF9283;
    --mark-soft: #3A1F25;
    --s3: #E8B85A;
    --warn-bg: #2D2611;
    --warn-fg: #F2D891;
    --warn-rule: #6E5823;
    --ok: #71D49C;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #0D1928;
  --surface: #0A1421;
  --pad: #10223A;
  --pad-line: #19324F;
  --ink: #E3EBF4;
  --ink-2: #A8B9CC;
  --ink-3: #8DA1B8;
  --rule: #243E5E;
  --rule-strong: #3E5F86;
  --accent: #84BAFF;
  --accent-ink: #0B1626;
  --accent-soft: #15304F;
  --mark: #FF9283;
  --mark-soft: #3A1F25;
  --s3: #E8B85A;
  --warn-bg: #2D2611;
  --warn-fg: #F2D891;
  --warn-rule: #6E5823;
  --ok: #71D49C;
  color-scheme: dark;
}

/* ------------------------------------------------------------------ base */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--f-body);
  font-size: var(--t-base);
  line-height: 1.6;
  text-rendering: optimizeLegibility;
}
img, svg { max-width: 100%; }
a { color: var(--accent); text-underline-offset: 0.18em; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
h1, h2, h3 { font-family: var(--f-display); font-weight: 700; line-height: 1.12; letter-spacing: 0.005em; text-wrap: balance; margin: 0; }
h1 { font-size: var(--t-xl); }
h2 { font-size: var(--t-lg); }
h3 { font-size: var(--t-md); }
p { margin: 0; }
code, kbd { font-family: var(--f-mono); font-size: 0.92em; }
code { background: var(--pad); padding: 0.05em 0.35em; border-radius: var(--radius); }
.wrap { max-width: 1200px; margin: 0 auto; padding-left: var(--gutter-l); padding-right: var(--gutter-r); }
.skip { position: absolute; left: -999px; top: 0; background: var(--accent); color: var(--accent-ink); padding: 8px 12px; z-index: 50; }
.skip:focus { left: var(--gutter-l); }
.eyebrow { font-family: var(--f-display); font-weight: 600; font-size: var(--t-sm); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-2); }
.lede { font-size: var(--t-md); line-height: 1.5; color: var(--ink-2); max-width: 62ch; }
.num, .mono { font-family: var(--f-mono); font-variant-numeric: tabular-nums; }
.vh { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------------------------------------------------------------- header */
.site-head { border-bottom: 1px solid var(--rule); background: var(--paper); }
.site-head__in { display: flex; align-items: center; justify-content: space-between; gap: 12px 24px; flex-wrap: wrap; padding-block: 14px; }
.brand { display: inline-flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; }
.brand__mark { width: 34px; height: 34px; flex: none; }
.brand__name { font-family: var(--f-display); font-weight: 700; font-size: 1.2rem; letter-spacing: 0.06em; text-transform: uppercase; line-height: 1; }
.site-nav { display: flex; gap: 4px 22px; flex-wrap: wrap; }
.site-nav a { font-family: var(--f-display); font-weight: 600; font-size: 1.0625rem; letter-spacing: 0.04em; text-transform: uppercase; color: var(--ink-2); text-decoration: none; padding-block: 4px; border-bottom: 2px solid transparent; }
.site-nav a:hover { color: var(--ink); }
.site-nav a[aria-current="page"] { color: var(--ink); border-bottom-color: var(--accent); }

/* ---------------------------------------------------------------- footer */
.site-foot { margin-top: 72px; border-top: 1px solid var(--rule); background: var(--pad); padding-block: 40px 28px; font-size: var(--t-sm); color: var(--ink-2); }
.foot-grid { display: grid; grid-template-columns: minmax(0, 1.4fr) repeat(3, minmax(0, 1fr)); gap: 28px; }
.foot-brand { display: grid; gap: 8px; align-content: start; }
.foot-brand__name { font-family: var(--f-display); font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--ink); font-size: 1rem; }
.foot-note { color: var(--ink-3); max-width: 40ch; }
.foot-col h2 { font-size: var(--t-sm); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink); margin-bottom: 8px; }
.foot-col ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.foot-col a { color: var(--ink-2); text-decoration: none; }
.foot-col a:hover { color: var(--accent); text-decoration: underline; }
.foot-copy { margin-top: 32px; padding-top: 16px; border-top: 1px solid var(--rule); color: var(--ink-3); }
@media (max-width: 860px) { .foot-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } .foot-brand { grid-column: 1 / -1; } }
@media (max-width: 460px) { .foot-grid { grid-template-columns: minmax(0, 1fr); } }

/* ----------------------------------------------------------- breadcrumbs */
.crumbs ol { list-style: none; margin: 0; padding: 18px 0 0; display: flex; flex-wrap: wrap; gap: 4px; font-size: var(--t-sm); color: var(--ink-3); }
.crumbs li + li::before { content: "/"; margin-right: 4px; color: var(--rule-strong); }
.crumbs a { color: var(--ink-2); text-decoration: none; }
.crumbs a:hover { color: var(--accent); text-decoration: underline; }

/* ------------------------------------------------------------- tool page */
.tool-head { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 20px 40px; align-items: end; padding-block: 18px 22px; }
.tool-head__text { display: grid; gap: 8px; }
.tool-head h1 { font-size: clamp(2rem, 4.2vw, var(--t-2xl)); }
.titleblock { display: grid; grid-template-columns: repeat(3, minmax(0, auto)); gap: 1px; margin: 0; background: var(--ink); border: 1.5px solid var(--ink); font-size: var(--t-sm); min-width: 280px; }
.titleblock > div { padding: 5px 10px 6px; background: var(--paper); }
.titleblock__wide { grid-column: 1 / -1; }
.titleblock dt { font-family: var(--f-display); font-weight: 600; font-size: 0.6875rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-3); }
.titleblock dd { margin: 0; font-family: var(--f-mono); font-weight: 500; color: var(--ink); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
@media (max-width: 720px) { .tool-head { grid-template-columns: minmax(0, 1fr); } .titleblock { min-width: 0; width: 100%; max-width: 360px; } }

.tool-grid { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 40px; align-items: start; }
.tool-main { min-width: 0; display: grid; gap: 28px; }
.tool-side { display: grid; gap: 24px; position: sticky; top: 16px; }
@media (max-width: 1099px) {
  .tool-grid { grid-template-columns: minmax(0, 1fr); }
  .tool-side { position: static; }
  .tool-side .ad--sidebar { display: none; }
}

.rel { border-top: 1.5px solid var(--ink); padding-top: 12px; }
.rel h2 { font-size: var(--t-sm); letter-spacing: 0.09em; text-transform: uppercase; margin-bottom: 8px; }
.rel ul { list-style: none; margin: 0; padding: 0; display: grid; }
.rel li a { display: grid; grid-template-columns: 76px minmax(0, 1fr); gap: 8px; padding: 9px 0; border-bottom: 1px solid var(--rule); color: var(--ink); text-decoration: none; font-weight: 500; line-height: 1.35; }
.rel li a:hover .rel__name { color: var(--accent); text-decoration: underline; }
.rel__no { font-family: var(--f-mono); font-size: var(--t-xs); color: var(--ink-3); padding-top: 2px; }
.rel__all { margin-top: 10px; font-size: var(--t-sm); }

/* ------------------------------------------------------------ calculator */
.calc {
  background-color: var(--pad);
  background-image:
    linear-gradient(var(--pad-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--pad-line) 1px, transparent 1px);
  background-size: var(--grid) var(--grid);
  background-position: -1px -1px;
  border: 1.5px solid var(--ink);
  border-radius: var(--radius);
}
.calc__bar { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 10px 16px; padding: 10px 14px; border-bottom: 1.5px solid var(--ink); background: var(--surface); border-radius: var(--radius) var(--radius) 0 0; }
.calc__bar-l, .calc__bar-r { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.calc__body { display: grid; grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.22fr); gap: 0; }
.calc__inputs { padding: 18px; display: grid; gap: 14px; align-content: start; border-right: 1px solid var(--rule-strong); }
.calc__outputs { padding: 18px; display: grid; gap: 16px; align-content: start; min-width: 0; }
.calc__wide { grid-column: 1 / -1; padding: 0 18px 18px; display: grid; gap: 18px; min-width: 0; }
.calc__section-title { font-family: var(--f-display); font-weight: 600; font-size: var(--t-sm); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-2); }
@media (max-width: 780px) {
  .calc__body { grid-template-columns: minmax(0, 1fr); }
  .calc__inputs { border-right: 0; border-bottom: 1px solid var(--rule-strong); }
}

.seg { display: inline-flex; border: 1px solid var(--ink); border-radius: var(--radius); overflow: hidden; background: var(--surface); }
.seg button { appearance: none; border: 0; background: transparent; color: var(--ink-2); font: 600 var(--t-sm)/1 var(--f-display); letter-spacing: 0.08em; text-transform: uppercase; padding: 8px 12px; cursor: pointer; }
.seg button + button { border-left: 1px solid var(--ink); }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--paper); }
.seg button:hover:not([aria-pressed="true"]) { background: var(--accent-soft); color: var(--ink); }
.seg-label { font: 600 var(--t-xs)/1 var(--f-display); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-3); }

.btn { appearance: none; display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--rule-strong); background: var(--surface); color: var(--ink); font: 500 var(--t-sm)/1 var(--f-body); padding: 8px 12px; border-radius: var(--radius); cursor: pointer; text-decoration: none; }
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn--primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn--primary:hover { color: var(--accent-ink); filter: brightness(1.08); }
.btn svg { width: 15px; height: 15px; flex: none; }

.field { display: grid; gap: 5px; }
.field[hidden] { display: none; }
.field__label { display: flex; align-items: baseline; justify-content: space-between; gap: 8px; font-size: var(--t-sm); font-weight: 500; color: var(--ink); }
.field__sym { font-family: var(--f-body); font-style: italic; color: var(--ink-2); font-weight: 400; }
.field__row { display: grid; grid-template-columns: minmax(0, 1fr) auto; }
.field__row--solo { grid-template-columns: minmax(0, 1fr); }
.input, .unit, .select {
  font: 400 1rem/1.2 var(--f-mono);
  color: var(--ink);
  background: var(--surface);
  border: 1px solid var(--rule-strong);
  padding: 9px 10px;
  min-width: 0;
  border-radius: var(--radius);
}
.field__row .input { border-radius: var(--radius) 0 0 var(--radius); }
.field__row--solo .input { border-radius: var(--radius); }
.unit { border-left: 0; border-radius: 0 var(--radius) var(--radius) 0; font-size: var(--t-sm); padding-right: 6px; background: var(--paper); cursor: pointer; }
.select { font-family: var(--f-body); font-size: var(--t-sm); width: 100%; cursor: pointer; }
.input:focus, .unit:focus, .select:focus { outline: 2px solid var(--accent); outline-offset: -1px; border-color: var(--accent); }
.input[aria-invalid="true"] { border-color: var(--mark); background: var(--mark-soft); }
.field__help { font-size: var(--t-xs); color: var(--ink-3); line-height: 1.45; }
.field__err { font-size: var(--t-xs); color: var(--mark); font-weight: 500; }
.field__err:empty { display: none; }
.input--expr { font-size: 1.05rem; }

.choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(92px, 1fr)); gap: 6px; }
.choice { appearance: none; display: grid; justify-items: center; gap: 4px; padding: 8px 6px 7px; border: 1px solid var(--rule-strong); background: var(--surface); color: var(--ink-2); border-radius: var(--radius); cursor: pointer; font: 500 var(--t-xs)/1.2 var(--f-body); text-align: center; }
.choice svg { width: 40px; height: 30px; }
.choice[aria-pressed="true"] { border-color: var(--ink); box-shadow: inset 0 0 0 1px var(--ink); color: var(--ink); background: var(--accent-soft); }
.choice:hover { border-color: var(--accent); }

/* results */
.results { display: grid; gap: 0; background: var(--surface); border: 1px solid var(--rule-strong); border-radius: var(--radius); }
.res-head, .res-row { display: grid; grid-template-columns: minmax(0, 1.25fr) repeat(var(--cols, 1), minmax(0, 1fr)) 84px; gap: 8px; align-items: center; padding: 9px 12px; }
.res-head { border-bottom: 1px solid var(--rule-strong); font: 600 var(--t-xs)/1.25 var(--f-display); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3); }
.res-head span:not(:first-child) { text-align: right; }
.res-row + .res-row { border-top: 1px solid var(--rule); }
.res-row__label { font-size: var(--t-sm); color: var(--ink-2); line-height: 1.3; }
.res-row__val { font-family: var(--f-mono); font-variant-numeric: tabular-nums; text-align: right; font-size: 1rem; color: var(--ink); white-space: nowrap; }
.res-row__val--text { font-family: var(--f-body); font-size: var(--t-sm); font-weight: 500; white-space: normal; }
.res-row__unit { font-size: var(--t-xs); padding: 4px 4px; border: 1px solid var(--rule); border-radius: var(--radius); background: var(--paper); color: var(--ink-2); font-family: var(--f-mono); width: 100%; min-width: 0; cursor: pointer; }
.res-row--primary .res-row__val { font-size: 1.25rem; font-weight: 500; }
.res-row--primary .res-row__label { color: var(--ink); font-weight: 600; }
.res-row__unit--static { border: 0; background: none; cursor: default; padding-left: 0; }
.res-empty { color: var(--ink-3); }
@media (max-width: 460px) {
  .res-head, .res-row { grid-template-columns: minmax(0, 0.9fr) repeat(var(--cols, 1), minmax(0, 1.05fr)) 62px; padding: 8px 9px; gap: 6px; }
  .res-row__val { font-size: 0.84rem; }
  .res-row--primary .res-row__val { font-size: 0.98rem; }
  .res-row__label { font-size: var(--t-xs); }
  .calc__bar { padding: 9px 10px; }
  .calc__bar .btn { padding: 7px 9px; gap: 5px; }
  .calc__bar-r { gap: 6px; }
}

.big { display: grid; gap: 2px; padding: 14px 14px 12px; background: var(--surface); border: 1px solid var(--rule-strong); border-left: 4px solid var(--accent); border-radius: var(--radius); }
.big__label { font: 600 var(--t-xs)/1.2 var(--f-display); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-3); }
.big__value { font: 500 clamp(1.5rem, 3vw, 2rem)/1.15 var(--f-mono); font-variant-numeric: tabular-nums; color: var(--ink); overflow-wrap: anywhere; }
.big__note { font-size: var(--t-sm); color: var(--ink-2); }
.big__label--math { font: 400 1rem/1.4 var(--f-body); letter-spacing: 0; text-transform: none; color: var(--ink-2); }
.big__label--math var { font-style: italic; }

.msgs { display: grid; gap: 8px; }
.msg { font-size: var(--t-sm); line-height: 1.45; padding: 9px 12px; border-radius: var(--radius); border: 1px solid var(--warn-rule); background: var(--warn-bg); color: var(--warn-fg); }
.msg--error { border-color: var(--mark); background: var(--mark-soft); color: var(--ink); }
.msg--info { border-color: var(--rule-strong); background: var(--surface); color: var(--ink-2); }
.msg--ok { border-color: var(--ok); background: var(--surface); color: var(--ink); }

/* diagrams and charts */
.figure { margin: 0; background: var(--surface); border: 1px solid var(--rule-strong); border-radius: var(--radius); padding: 10px 12px 8px; min-width: 0; }
.figure__head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 4px 14px; margin-bottom: 4px; }
.figure__title { font: 600 var(--t-sm)/1.3 var(--f-display); letter-spacing: 0.06em; text-transform: uppercase; color: var(--ink); }
.legend { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: var(--t-xs); color: var(--ink-2); }
.legend span { display: inline-flex; align-items: center; gap: 6px; }
.legend svg { width: 22px; height: 8px; }
.chart { position: relative; }
.chart svg { display: block; width: 100%; height: auto; overflow: visible; touch-action: pan-y; }
.chart text { font-family: var(--f-mono); font-size: 11px; fill: var(--ink-3); }
.chart .ax-title { font-family: var(--f-body); font-size: 11.5px; fill: var(--ink-2); }
.chart .grid { stroke: var(--pad-line); stroke-width: 1; }
.chart .axis { stroke: var(--rule-strong); stroke-width: 1; }
.chart .zero { stroke: var(--ink-3); stroke-width: 1; }
.chart .s1 { stroke: var(--accent); fill: none; stroke-width: 2.25; }
.chart .s2 { stroke: var(--mark); fill: none; stroke-width: 2.25; stroke-dasharray: 7 4; }
.chart .s3 { stroke: var(--s3); fill: none; stroke-width: 2; stroke-dasharray: 2 3; }
.chart .f1 { fill: var(--accent); opacity: 0.1; stroke: none; }
.chart .f2 { fill: var(--mark); opacity: 0.1; stroke: none; }
.chart .f3 { fill: var(--s3); opacity: 0.12; stroke: none; }
.chart .guide { stroke: var(--ink-3); stroke-width: 1; stroke-dasharray: 3 3; }
.chart .dot1 { fill: var(--accent); } .chart .dot2 { fill: var(--mark); } .chart .dot3 { fill: var(--s3); }
.chart .pt { fill: var(--surface); stroke: var(--ink); stroke-width: 1.5; }
.chart__tip { position: absolute; pointer-events: none; background: var(--ink); color: var(--paper); font: 500 var(--t-xs)/1.45 var(--f-mono); padding: 6px 8px; border-radius: var(--radius); white-space: nowrap; transform: translate(-50%, calc(-100% - 10px)); z-index: 3; }
.chart__tip[hidden] { display: none; }
.chart__tip b { font-weight: 500; }
.chart__tip i { display: inline-block; width: 8px; height: 8px; border-radius: 50%; margin-right: 5px; vertical-align: 0; }
.charts { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 340px), 1fr)); gap: 14px; }
.charts .figure--full { grid-column: 1 / -1; }

.diagram svg { display: block; width: 100%; height: auto; }
.diagram text { font-family: var(--f-mono); font-size: 12px; fill: var(--ink-2); }
.diagram .d-member { fill: var(--accent-soft); stroke: var(--ink); stroke-width: 1.5; }
.diagram .d-line { stroke: var(--ink); stroke-width: 1.5; fill: none; }
.diagram .d-thin { stroke: var(--ink-3); stroke-width: 1; fill: none; }
.diagram .d-fill { fill: var(--surface); stroke: var(--ink); stroke-width: 1.5; }
.diagram .d-hatch { stroke: var(--ink-3); stroke-width: 1; }
.diagram .d-load1 { stroke: var(--accent); fill: var(--accent); stroke-width: 1.75; }
.diagram .d-load2 { stroke: var(--mark); fill: var(--mark); stroke-width: 1.5; }
.diagram .d-defl { stroke: var(--ink-3); stroke-width: 1.25; fill: none; stroke-dasharray: 5 4; }
.diagram .d-dim { stroke: var(--ink-3); stroke-width: 1; fill: var(--ink-3); }
.diagram .d-label1 { fill: var(--accent); font-weight: 500; }
.diagram .d-label2 { fill: var(--mark); font-weight: 500; }
.diagram .d-section { fill: var(--accent-soft); stroke: var(--ink); stroke-width: 1.5; fill-rule: evenodd; }
.diagram .d-axis { stroke: var(--mark); stroke-width: 1; stroke-dasharray: 8 3 2 3; }

.calc__foot { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 6px 16px; padding: 10px 14px; border-top: 1px solid var(--rule-strong); background: var(--surface); border-radius: 0 0 var(--radius) var(--radius); font-size: var(--t-xs); color: var(--ink-3); }
.toast { font-size: var(--t-sm); color: var(--ok); font-weight: 500; }
.toast:empty { display: none; }

.results--calc .res-row, .results--calc .res-head { grid-template-columns: minmax(0, 0.8fr) minmax(0, 1.6fr); }
.results--rules .res-row, .results--rules .res-head { grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr) minmax(0, 0.8fr); }
.results:empty { display: none; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { appearance: none; border: 1px solid var(--rule-strong); background: var(--surface); color: var(--ink-2); font: 400 var(--t-sm)/1 var(--f-mono); padding: 6px 9px; border-radius: 999px; cursor: pointer; }
.chip:hover { border-color: var(--accent); color: var(--accent); }
.field-pair { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.calc__bar .seg-label { margin-right: 2px; }

/* math output */
.msqrt { white-space: nowrap; }
.msqrt__in { border-top: 1px solid currentColor; padding: 0 0.12em; margin-left: 0.04em; }
.msqrt__idx { font-size: 0.6em; margin-right: -0.35em; vertical-align: 0.9em; }
.mathout sup { font-size: 0.72em; }
.mathout .fr { font-size: 0.95em; }
.mathout { font-family: var(--f-body); font-size: 1.2rem; line-height: 2.1; color: var(--ink); overflow-x: auto; padding: 4px 2px; }
.mathout var, .eq var { font-style: italic; font-family: var(--f-body); }
.mathout .mfn, .eq .mfn { font-style: normal; }
.plain { font-family: var(--f-mono); font-size: var(--t-sm); color: var(--ink-2); overflow-wrap: anywhere; }

/* --------------------------------------------------------------- article */
.article { display: grid; gap: 18px; max-width: 72ch; }
.article > h2 { margin-top: 18px; padding-top: 14px; border-top: 1.5px solid var(--ink); }
.article > h3 { margin-top: 6px; }
.article ul, .article ol { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; }
.article li::marker { color: var(--ink-3); }
.eq { display: block; font-size: 1.15rem; line-height: 2.4; padding: 10px 18px 12px; background: var(--surface); border: 1px solid var(--rule); border-left: 3px solid var(--ink); overflow-x: auto; }
.eq__name { display: block; font: 600 var(--t-xs)/1.2 var(--f-display); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-3); margin-bottom: 2px; }
.eq sub, .eq sup { line-height: 0; }
.eqs { display: grid; gap: 10px; }
.fr { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; margin: 0 0.15em; line-height: 1.25; }
.fr > span { padding: 0 0.25em; }
.fr > span + span { border-top: 1px solid currentColor; }
.vars { width: 100%; border-collapse: collapse; font-size: var(--t-sm); }
.vars th, .vars td { text-align: left; padding: 7px 10px; border-bottom: 1px solid var(--rule); vertical-align: top; }
.vars th { font: 600 var(--t-xs)/1.2 var(--f-display); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3); border-bottom: 1.5px solid var(--ink); }
.vars td:first-child { font-style: italic; white-space: nowrap; }
.table-wrap { overflow-x: auto; }
.example { background: var(--surface); border: 1px solid var(--rule-strong); border-radius: var(--radius); padding: 16px 18px; display: grid; gap: 10px; }
.example__title { font: 600 var(--t-sm)/1.2 var(--f-display); letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-2); }
.example ol { padding-left: 1.2em; }
.notice { font-size: var(--t-sm); color: var(--ink-2); border: 1px dashed var(--rule-strong); padding: 12px 14px; border-radius: var(--radius); }
.faq { display: grid; gap: 0; border-top: 1px solid var(--rule); }
.faq details { border-bottom: 1px solid var(--rule); padding: 12px 0; }
.faq summary { cursor: pointer; font-weight: 600; list-style: none; display: flex; justify-content: space-between; gap: 12px; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; font-family: var(--f-mono); color: var(--ink-3); }
.faq details[open] summary::after { content: "−"; }
.faq details > div { padding-top: 8px; color: var(--ink-2); display: grid; gap: 8px; }

/* ------------------------------------------------------------------- ads */
.ad { display: grid; gap: 4px; justify-items: center; min-width: 0; }
.ad__label { font: 600 0.625rem/1 var(--f-display); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-3); }
.ad ins { width: 100%; min-height: 90px; }
.ad--sidebar ins { min-height: 600px; }
.ad:has(ins[data-ad-status="unfilled"]) { display: none; }
.ad__box { width: 100%; display: grid; place-content: center; gap: 4px; text-align: center; border: 1.5px dashed var(--rule-strong); border-radius: var(--radius); color: var(--ink-3); background: repeating-linear-gradient(-45deg, transparent 0 9px, var(--pad) 9px 10px); padding: 14px; }
.ad__box strong { font: 600 var(--t-sm)/1.2 var(--f-display); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-2); }
.ad__box small { font-size: var(--t-xs); }
.ad--below_calculator .ad__box, .ad--end_of_page .ad__box, .ad--in_article .ad__box { min-height: 100px; }
.ad--sidebar .ad__box { min-height: 600px; }
.ad--end_of_page { margin-top: 32px; }

/* ------------------------------------------------------------------ home */
.hero { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr); gap: 32px 56px; align-items: center; padding-block: 52px 40px; }
.hero__text { display: grid; gap: 18px; }
.hero h1 { font-size: clamp(2.4rem, 5.4vw, 4rem); line-height: 1.02; letter-spacing: 0; }
.hero h1 em { font-style: normal; color: var(--accent); }
.hero__cta { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 4px; }
.hero__cta .btn { padding: 11px 16px; font-size: 1rem; }
.hero__sheet { background: var(--pad); background-image: linear-gradient(var(--pad-line) 1px, transparent 1px), linear-gradient(90deg, var(--pad-line) 1px, transparent 1px); background-size: var(--grid) var(--grid); border: 1.5px solid var(--ink); border-radius: var(--radius); padding: 16px 18px 12px; }
.hero__sheet svg { display: block; width: 100%; height: auto; }
.hero__sheet text { font-family: var(--f-mono); font-size: 13px; fill: var(--ink-2); }
.hero__sheet .h-beam { fill: var(--accent-soft); stroke: var(--ink); stroke-width: 1.6; }
.hero__sheet .h-ink { stroke: var(--ink); stroke-width: 1.6; fill: none; }
.hero__sheet .h-thin { stroke: var(--ink-3); stroke-width: 1; fill: none; }
.hero__sheet .h-fill { fill: var(--surface); stroke: var(--ink); stroke-width: 1.6; }
.hero__sheet .h-load { stroke: var(--mark); stroke-width: 1.6; fill: var(--mark); }
.hero__sheet .h-defl { stroke: var(--accent); stroke-width: 2; fill: none; stroke-dasharray: 6 4; }
.hero__sheet .h-red { fill: var(--mark); font-weight: 500; }
.hero__sheet .h-blue { fill: var(--accent); font-weight: 500; }
.hero__sheet .h-hand { font-family: var(--f-body); font-style: italic; font-size: 15px; fill: var(--ink); }
.hero__sheet-foot { display: flex; justify-content: space-between; gap: 10px; flex-wrap: wrap; border-top: 1px solid var(--rule-strong); margin-top: 6px; padding-top: 8px; font: 500 var(--t-xs)/1.3 var(--f-mono); color: var(--ink-3); }
@media (max-width: 900px) { .hero { grid-template-columns: minmax(0, 1fr); padding-block: 32px 24px; } }

.finder { display: grid; gap: 22px; padding-block: 12px 8px; }
.finder__head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: end; gap: 12px 24px; border-top: 1.5px solid var(--ink); padding-top: 18px; }
.finder__search { position: relative; width: min(100%, 340px); }
.finder__search input { width: 100%; font: 400 1rem/1.2 var(--f-body); padding: 10px 12px 10px 36px; border: 1px solid var(--rule-strong); border-radius: var(--radius); background: var(--surface); color: var(--ink); }
.finder__search svg { position: absolute; left: 11px; top: 50%; transform: translateY(-50%); width: 16px; height: 16px; color: var(--ink-3); }
.finder__group { display: grid; gap: 12px; }
.finder__group[hidden] { display: none; }
.finder__group h3 { display: flex; align-items: baseline; gap: 10px; font-size: var(--t-md); }
.finder__group h3 a { color: inherit; text-decoration: none; }
.finder__group h3 a:hover { color: var(--accent); }
.finder__group h3 small { font: 500 var(--t-xs)/1 var(--f-mono); color: var(--ink-3); letter-spacing: 0; }
.finder__empty { color: var(--ink-3); }

.tcards { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 260px), 1fr)); gap: 12px; }
.tcard[hidden] { display: none; }
.tcard__link { height: 100%; display: grid; grid-template-rows: auto auto 1fr auto; gap: 6px; padding: 14px 16px 12px; background: var(--surface); border: 1px solid var(--rule-strong); border-radius: var(--radius); color: var(--ink); text-decoration: none; transition: border-color 0.12s, transform 0.12s; }
.tcard__link:hover { border-color: var(--ink); transform: translateY(-1px); }
.tcard__link:hover .tcard__name { color: var(--accent); }
.tcard__no { font: 500 var(--t-xs)/1 var(--f-mono); color: var(--ink-3); }
.tcard__name { font: 700 1.3rem/1.15 var(--f-display); }
.tcard__desc { font-size: var(--t-sm); color: var(--ink-2); line-height: 1.5; }
.tcard__meta { font: 600 var(--t-xs)/1 var(--f-display); letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3); border-top: 1px solid var(--rule); padding-top: 9px; margin-top: 4px; }

.method { display: grid; grid-template-columns: minmax(0, 0.9fr) minmax(0, 2fr); gap: 24px 48px; padding-block: 48px 8px; }
.method__intro { display: grid; gap: 12px; align-content: start; }
.method__list { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0; border-top: 1.5px solid var(--ink); }
.method__list li { padding: 16px 18px 18px 0; border-bottom: 1px solid var(--rule); display: grid; gap: 6px; }
.method__list li:nth-child(2n) { padding-left: 18px; border-left: 1px solid var(--rule); }
.method__list h3 { font-size: 1.15rem; }
.method__list p { font-size: var(--t-sm); color: var(--ink-2); }
@media (max-width: 860px) { .method { grid-template-columns: minmax(0, 1fr); } }
@media (max-width: 560px) { .method__list { grid-template-columns: minmax(0, 1fr); } .method__list li:nth-child(2n) { padding-left: 0; border-left: 0; } }

/* -------------------------------------------------------- category/static */
.cat { display: grid; gap: 24px; }
.cat-head { display: grid; gap: 10px; padding-block: 18px 6px; }
.prose { max-width: 72ch; display: grid; gap: 16px; padding-block: 8px 0; }
.prose h1 { margin-top: 18px; }
.prose h2 { margin-top: 18px; padding-top: 12px; border-top: 1.5px solid var(--ink); }
.prose ul, .prose ol { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; }
.prose .updated { color: var(--ink-3); font-size: var(--t-sm); }
.contact-card { display: grid; gap: 10px; padding: 18px; background: var(--surface); border: 1.5px solid var(--ink); border-radius: var(--radius); max-width: 520px; }
.contact-card .mono { font-size: 1.05rem; overflow-wrap: anywhere; }
.e404 { display: grid; gap: 16px; padding-block: 64px 24px; justify-items: start; }
.e404 .num { font-size: 4rem; line-height: 1; color: var(--mark); }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; scroll-behavior: auto !important; }
}
@media print {
  .site-head, .site-foot, .ad, .tool-side, .calc__bar, .crumbs { display: none !important; }
  .tool-grid { display: block; }
  .calc { background: none; }
}