/* ==========================================================================
   Online Cubic Feet Calculator — design system
   System font stack only. No webfonts, no icon fonts, no external requests.
   ========================================================================== */

:root{
  --bg:#FBFBFD;
  --surface:#FFFFFF;
  --surface-2:#F5F5F7;
  --surface-3:#EFEFF2;
  --line:rgba(0,0,0,.09);
  --line-soft:rgba(0,0,0,.055);
  --ink:#1D1D1F;
  --ink-2:#4A4A4F;
  --ink-3:#86868B;
  --accent:#3747D6;
  --accent-dark:#2A37AE;
  --accent-soft:#EEF0FD;
  --accent-line:rgba(55,71,214,.26);
  --good:#0A7C4A;
  --warn:#9A5B00;
  --r-xl:20px;
  --r-lg:14px;
  --r-md:10px;
  --r-sm:7px;
  --sh-1:0 1px 2px rgba(16,24,40,.05);
  --sh-2:0 2px 6px rgba(16,24,40,.06), 0 1px 2px rgba(16,24,40,.04);
  --sh-3:0 18px 48px -18px rgba(16,24,40,.22), 0 2px 6px rgba(16,24,40,.05);
  --font:-apple-system,BlinkMacSystemFont,"SF Pro Text","Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  --mono:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Consolas,monospace;
  --wrap:1180px;
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth;scroll-padding-top:92px;overflow-x:clip}
body{
  margin:0;background:var(--bg);color:var(--ink);font-family:var(--font);
  overflow-x:clip;max-width:100vw;
  font-size:17px;line-height:1.6;letter-spacing:-.011em;
  -webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;
}
img,svg{max-width:100%;display:block}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px;border-radius:4px}
::selection{background:var(--accent-soft)}

.wrap{width:100%;max-width:var(--wrap);margin-inline:auto;padding-inline:22px}

/* Grid and flex children default to min-width:auto, which makes them refuse to
   shrink below their content and pushes the whole page wider than the screen.
   Every track in this layout is allowed to shrink instead. */
.calc-grid>*,.fields>*,.row-2>*,.body-layout>*,.units>*,.strip>*,.cats>*,
.posts>*,.foot-grid>*,.pane>*,.results>*,.addons>*,.card-body>*,.items>*{min-width:0}
.tabnum{font-variant-numeric:tabular-nums;font-feature-settings:"tnum" 1}
.vh{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}

/* ---------- Type scale ---------- */
h1,h2,h3,h4{margin:0;letter-spacing:-.028em;line-height:1.12;font-weight:650}
h1{font-size:clamp(2.1rem,1.4rem + 2.9vw,3.5rem);letter-spacing:-.035em}
h2{font-size:clamp(1.5rem,1.2rem + 1.1vw,2.1rem);margin-top:0}
h3{font-size:1.19rem;letter-spacing:-.02em}
h4{font-size:1.02rem}
p{margin:0 0 1.1em}
.lede{font-size:clamp(1.06rem,1rem + .35vw,1.28rem);color:var(--ink-2);line-height:1.55;letter-spacing:-.014em}
.eyebrow{
  font-size:.74rem;font-weight:640;letter-spacing:.1em;text-transform:uppercase;
  color:var(--accent);margin:0 0 .7rem;
}

/* ---------- Header ---------- */
.site-head{
  position:sticky;top:0;z-index:60;
  background:rgba(251,251,253,.82);
  -webkit-backdrop-filter:saturate(180%) blur(20px);
  backdrop-filter:saturate(180%) blur(20px);
  border-bottom:1px solid var(--line-soft);
}
.head-in{display:flex;align-items:center;gap:20px;height:60px}
.brand{display:flex;align-items:center;flex:none}
.brand:hover{text-decoration:none;opacity:.78}
.brand img{width:122px;height:34px;display:block}
@media (max-width:400px){.brand img{width:104px;height:29px}}

.nav{margin-left:auto;display:flex;align-items:center;gap:2px}
.nav a{
  color:var(--ink-2);font-size:.9rem;font-weight:500;padding:7px 12px;border-radius:var(--r-sm);
  white-space:nowrap;
}
.nav a:hover{color:var(--ink);background:var(--surface-3);text-decoration:none}
.nav .has-sub{position:relative}
.nav .has-sub>button{
  font:inherit;font-size:.9rem;font-weight:500;color:var(--ink-2);background:none;border:0;
  padding:7px 10px 7px 12px;border-radius:var(--r-sm);cursor:pointer;display:flex;align-items:center;gap:5px;
}
.nav .has-sub>button:hover{color:var(--ink);background:var(--surface-3)}
.nav .has-sub>button svg{width:11px;height:11px;transition:transform .18s ease}
.nav .has-sub[data-open="true"]>button svg{transform:rotate(180deg)}
.submenu{
  position:absolute;top:calc(100% + 8px);right:0;min-width:238px;
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  box-shadow:var(--sh-3);padding:6px;display:none;
}
.nav .has-sub[data-open="true"] .submenu{display:block}
.submenu a{display:block;padding:8px 11px;font-size:.88rem;border-radius:var(--r-sm)}
.submenu a small{display:block;color:var(--ink-3);font-size:.76rem;font-weight:450;margin-top:1px}

.burger{
  margin-left:auto;display:none;background:none;border:1px solid var(--line);border-radius:var(--r-md);
  width:44px;height:40px;align-items:center;justify-content:center;cursor:pointer;
  color:#1D1D1F;position:relative;flex:none;-webkit-tap-highlight-color:transparent
}
.burger svg{display:none}
.burger::before{
  content:"";width:17px;height:11px;
  border-top:1.8px solid currentColor;border-bottom:1.8px solid currentColor;
  position:relative;
}
.burger::after{content:"";position:absolute;width:17px;height:0;border-top:1.8px solid currentColor}
.burger[aria-expanded="true"]::before{border-color:transparent;transform:rotate(45deg)}
.burger[aria-expanded="true"]::after{transform:rotate(-45deg)}
.burger[aria-expanded="true"]::before{border-top-color:currentColor;height:0;transform:rotate(45deg)}

/* ---------- Hero ---------- */
.hero{padding:52px 0 12px;text-align:center}
.hero h1{max-width:16ch;margin-inline:auto}
.hero .lede{max-width:58ch;margin:.85rem auto 0}
.trust{
  display:flex;flex-wrap:wrap;gap:6px 20px;justify-content:center;margin:1.5rem 0 0;
  padding:0;list-style:none;font-size:.855rem;color:var(--ink-3);
}
.trust li{display:flex;align-items:center;gap:6px}
.trust svg{width:14px;height:14px;color:var(--good);flex:none}

/* ==========================================================================
   Calculator
   ========================================================================== */
.calc{
  margin:30px 0 0;background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r-xl);box-shadow:var(--sh-3);overflow:hidden;
}
.calc-grid{display:grid;grid-template-columns:minmax(0,1.32fr) minmax(0,1fr)}

/* --- shape rail --- */
.shapes{
  display:flex;gap:6px;overflow-x:auto;padding:14px 18px;border-bottom:1px solid var(--line-soft);
  background:var(--surface-2);scrollbar-width:thin;
}
.shapes{-webkit-overflow-scrolling:touch;scroll-snap-type:x proximity;overscroll-behavior-x:contain}
.shape-btn{scroll-snap-align:start}
.shapes::-webkit-scrollbar{height:5px}
.shapes::-webkit-scrollbar-thumb{background:rgba(0,0,0,.16);border-radius:4px}
.shape-btn{
  flex:none;display:flex;flex-direction:column;align-items:center;gap:5px;
  min-width:72px;padding:9px 8px 7px;border:1px solid transparent;border-radius:var(--r-md);
  background:transparent;cursor:pointer;font:inherit;font-size:.735rem;font-weight:520;
  color:var(--ink-2);letter-spacing:-.005em;line-height:1.2;text-align:center;
  transition:background .15s ease,color .15s ease,border-color .15s ease;
}
.shape-btn svg{width:26px;height:26px;color:var(--ink-3);transition:color .15s ease}
.shape-btn:hover{background:rgba(0,0,0,.04)}
.shape-btn[aria-pressed="true"]{background:var(--surface);border-color:var(--line);box-shadow:var(--sh-1);color:var(--ink)}
.shape-btn[aria-pressed="true"] svg{color:var(--accent)}

/* --- input pane --- */
.pane{padding:22px}
.pane-head{display:flex;align-items:baseline;justify-content:space-between;gap:12px;margin-bottom:16px}
.pane-head h2{font-size:1.05rem;font-weight:620;letter-spacing:-.018em}
.pane-head p{margin:0;font-size:.84rem;color:var(--ink-3)}

.fields{display:grid;gap:12px}
.field label{display:block;font-size:.83rem;font-weight:560;color:var(--ink-2);margin-bottom:5px}
.field label .sym{color:var(--ink-3);font-weight:450;font-style:italic}
.control{
  display:flex;align-items:stretch;min-width:0;width:100%;
  border:1px solid var(--line);border-radius:var(--r-md);background:var(--surface);
  box-shadow:var(--sh-1);transition:border-color .15s ease,box-shadow .15s ease;overflow:hidden;
}
.control:focus-within{border-color:var(--accent);box-shadow:0 0 0 3.5px rgba(55,71,214,.14)}
.control input{
  flex:1 1 0%;min-width:0;width:auto;border:0;background:none;font:inherit;font-size:1.05rem;
  font-variant-numeric:tabular-nums;padding:13px 14px;color:var(--ink);
}
.control input:focus{outline:none}
.control input::placeholder{color:#B9B9BE}
.control select{
  flex:0 0 92px !important;width:92px !important;min-width:92px;max-width:92px;
  border:0;border-left:1px solid var(--line-soft);background:var(--surface-2);
  font:inherit;font-size:.88rem;font-weight:540;color:var(--ink-2);padding:0 26px 0 12px;cursor:pointer;
  text-align:left;
  -webkit-appearance:none;appearance:none;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 10 6'%3E%3Cpath d='M1 1l4 4 4-4' fill='none' stroke='%2386868B' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat:no-repeat;background-position:right 11px center;background-size:9px;
}
.control select:focus{outline:none}
#cfc-currency{flex:0 0 62px !important;width:62px !important;min-width:62px;max-width:62px}
/* Full-width selects that sit alone in a control, not beside an input. */
.control>select:only-child{flex:1 1 auto !important;width:100% !important;max-width:none;min-width:0;border-left:0}
.field.bad .control{border-color:#C4362F}
.field-note{margin:5px 0 0;font-size:.78rem;color:var(--ink-3)}
.field-note b{color:var(--ink-2);font-weight:560;font-family:var(--mono);font-size:.94em}

.row-2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}

.pane-actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:7px;
  font:inherit;font-size:.875rem;font-weight:560;letter-spacing:-.008em;
  padding:9px 15px;border-radius:999px;border:1px solid var(--line);
  background:var(--surface);color:var(--ink);cursor:pointer;box-shadow:var(--sh-1);
  transition:background .15s ease,border-color .15s ease,transform .08s ease;
}
.btn svg{width:14px;height:14px;flex:none}
.btn:hover{background:var(--surface-2);text-decoration:none}
.btn:active{transform:scale(.985)}
.btn-primary{background:var(--accent);border-color:var(--accent);color:#fff}
.btn-primary:hover{background:var(--accent-dark);border-color:var(--accent-dark)}
.btn-quiet{border-color:transparent;box-shadow:none;background:transparent;color:var(--ink-2)}
.btn-quiet:hover{background:var(--surface-3)}

/* --- diagram --- */
.diagram{
  margin-top:20px;padding:16px;background:var(--surface-2);border-radius:var(--r-lg);
  border:1px solid var(--line-soft);
}
.diagram svg{width:100%;height:auto;max-height:190px;margin-inline:auto}
.dg-face{fill:rgba(55,71,214,.07);stroke:var(--accent);stroke-width:1.6;stroke-linejoin:round}
.dg-hidden{fill:none;stroke:var(--accent-line);stroke-width:1.2;stroke-dasharray:3 3}
.dg-dim{stroke:var(--ink-3);stroke-width:1;fill:none}
.dg-label{fill:var(--ink-2);font-size:11px;font-family:var(--font);font-weight:560}
.dg-label.on{fill:var(--accent)}

/* --- results pane --- */
.results{background:var(--surface-2);border-left:1px solid var(--line-soft);padding:22px;display:flex;flex-direction:column}
.headline{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  padding:18px 20px;box-shadow:var(--sh-1);
}
.headline .k{font-size:.78rem;font-weight:600;letter-spacing:.07em;text-transform:uppercase;color:var(--ink-3)}
.headline .v{
  display:flex;align-items:baseline;gap:8px;margin-top:4px;
  font-size:clamp(2rem,1.4rem + 2.1vw,2.9rem);font-weight:640;letter-spacing:-.038em;
  color:var(--ink);font-variant-numeric:tabular-nums;line-height:1.05;
}
.headline .v em{font-style:normal;font-size:.42em;font-weight:560;color:var(--ink-3);letter-spacing:-.01em}
.headline .sub{margin:7px 0 0;font-size:.85rem;color:var(--ink-3)}
.headline.empty .v{color:#C7C7CC}

.units{list-style:none;margin:14px 0 0;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:1px;
  background:var(--line-soft);border:1px solid var(--line-soft);border-radius:var(--r-lg);overflow:hidden}
.units li{background:var(--surface);padding:10px 13px;display:flex;flex-direction:column;gap:1px}
.units .k{font-size:.75rem;color:var(--ink-3);font-weight:520}
.units .v{font-size:.97rem;font-weight:580;font-variant-numeric:tabular-nums;letter-spacing:-.015em}

/* --- accordions --- */
.addons{margin-top:14px;display:grid;gap:8px}
details.card{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  box-shadow:var(--sh-1);overflow:hidden;
}
details.card>summary{
  list-style:none;cursor:pointer;padding:12px 15px;display:flex;align-items:center;gap:10px;
  font-size:.885rem;font-weight:560;letter-spacing:-.01em;
}
details.card>summary::-webkit-details-marker{display:none}
details.card>summary:hover{background:var(--surface-2)}
details.card>summary .ico{width:16px;height:16px;color:var(--accent);flex:none}
details.card>summary .chev{width:11px;height:11px;margin-left:auto;color:var(--ink-3);transition:transform .18s ease}
details.card[open]>summary .chev{transform:rotate(180deg)}
details.card[open]>summary{border-bottom:1px solid var(--line-soft)}
.card-body{padding:14px 15px}
.card-body>*:last-child{margin-bottom:0}

.mini{display:grid;gap:10px}
.mini label{display:block;font-size:.8rem;font-weight:550;color:var(--ink-2);margin-bottom:4px}

.readout{display:flex;justify-content:space-between;gap:12px;padding:8px 0;border-bottom:1px solid var(--line-soft);font-size:.885rem}
.readout:last-child{border-bottom:0}
.readout .k{color:var(--ink-2)}
.readout .v{font-weight:600;font-variant-numeric:tabular-nums;text-align:right}
.readout.big .v{color:var(--accent);font-size:1.02rem}

.math{font-family:var(--mono);font-size:.83rem;line-height:1.75;color:var(--ink-2);margin:0;white-space:pre-wrap;word-break:break-word}
.math b{color:var(--ink);font-weight:640}

/* --- item list --- */
.items{list-style:none;margin:0 0 12px;padding:0;display:grid;gap:6px}
.items li{
  display:flex;align-items:center;gap:10px;padding:8px 11px;background:var(--surface-2);
  border:1px solid var(--line-soft);border-radius:var(--r-md);font-size:.85rem;
}
.items .nm{flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.items .nm small{display:block;color:var(--ink-3);font-size:.78rem}
.items .qt{font-weight:600;font-variant-numeric:tabular-nums;white-space:nowrap}
.items .x{background:none;border:0;cursor:pointer;color:var(--ink-3);padding:2px;line-height:0;border-radius:4px}
.items .x:hover{color:#C4362F;background:rgba(196,54,47,.08)}
.items .x svg{width:13px;height:13px}
.empty-note{margin:0 0 12px;font-size:.84rem;color:var(--ink-3)}

.total-bar{
  display:flex;align-items:center;justify-content:space-between;gap:12px;padding:12px 14px;
  background:var(--accent-soft);border:1px solid var(--accent-line);border-radius:var(--r-md);
}
.total-bar .k{font-size:.83rem;font-weight:560;color:var(--accent-dark)}
.total-bar .v{font-size:1.15rem;font-weight:660;font-variant-numeric:tabular-nums;color:var(--accent-dark);letter-spacing:-.02em}

.toast{
  position:fixed;left:50%;bottom:26px;transform:translate(-50%,14px);z-index:90;
  background:#1D1D1F;color:#fff;font-size:.86rem;font-weight:520;padding:10px 18px;border-radius:999px;
  box-shadow:var(--sh-3);opacity:0;pointer-events:none;transition:opacity .2s ease,transform .2s ease;
}
.toast.on{opacity:1;transform:translate(-50%,0)}

/* ==========================================================================
   Content
   ========================================================================== */
.strip{margin:34px 0 0;display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px}
.stat{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);padding:15px 17px;box-shadow:var(--sh-1)}
.stat .v{font-size:1.28rem;font-weight:650;letter-spacing:-.028em;font-variant-numeric:tabular-nums}
.stat .k{font-size:.815rem;color:var(--ink-3);margin-top:2px}

.body-layout{display:grid;grid-template-columns:214px minmax(0,1fr);gap:56px;margin:64px 0 0;align-items:start}
.toc{position:sticky;top:86px}
.toc h2{font-size:.74rem;font-weight:640;letter-spacing:.09em;text-transform:uppercase;color:var(--ink-3);margin-bottom:11px}
.toc ol{list-style:none;margin:0;padding:0;display:grid;gap:1px;counter-reset:t}
.toc a{
  display:block;font-size:.855rem;color:var(--ink-2);padding:5px 10px;border-radius:var(--r-sm);
  border-left:2px solid transparent;line-height:1.35;
}
.toc a:hover{color:var(--ink);background:var(--surface-2);text-decoration:none}
.toc a.on{color:var(--accent);border-left-color:var(--accent);background:var(--accent-soft);font-weight:560}

.article{max-width:74ch}
.article section{margin-bottom:52px;scroll-margin-top:92px}
.article section:last-child{margin-bottom:0}
.article h2{margin-bottom:.5em}
.article h3{margin:1.9em 0 .55em}
.article h4{margin:1.5em 0 .4em}
.article ul,.article ol{margin:0 0 1.1em;padding-left:1.25em}
.article li{margin-bottom:.42em}
.article li::marker{color:var(--ink-3)}

.callout{
  background:var(--surface);border:1px solid var(--line);border-left:3px solid var(--accent);
  border-radius:var(--r-md);padding:14px 17px;margin:0 0 1.3em;font-size:.945rem;box-shadow:var(--sh-1);
}
.callout p:last-child{margin-bottom:0}
.callout strong{font-weight:620}

.formula{
  background:var(--surface-2);border:1px solid var(--line-soft);border-radius:var(--r-md);
  padding:13px 16px;margin:0 0 1.3em;font-family:var(--mono);font-size:.92rem;color:var(--ink);
  overflow-x:auto;white-space:nowrap;
}
.worked{
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  padding:17px 19px;margin:0 0 1.3em;box-shadow:var(--sh-1);
}
.worked h4{margin:0 0 .55em;font-size:.79rem;letter-spacing:.08em;text-transform:uppercase;color:var(--accent);font-weight:640}
.worked ol{margin:0;padding-left:1.15em}
.worked ol li{margin-bottom:.35em;font-size:.94rem}
.worked .res{margin:.9em 0 0;padding-top:.75em;border-top:1px solid var(--line-soft);font-weight:620;font-size:.98rem}

.tbl-scroll{overflow-x:auto;-webkit-overflow-scrolling:touch;margin:0 0 1.3em;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);box-shadow:var(--sh-1)}
table{border-collapse:collapse;width:100%;font-size:.9rem;min-width:420px}
caption{text-align:left;font-size:.84rem;color:var(--ink-3);padding:11px 15px 0}
th,td{padding:10px 15px;text-align:left;border-bottom:1px solid var(--line-soft);vertical-align:top}
thead th{font-size:.76rem;font-weight:620;letter-spacing:.055em;text-transform:uppercase;color:var(--ink-3);background:var(--surface-2)}
tbody tr:last-child td{border-bottom:0}
td.num{font-variant-numeric:tabular-nums;white-space:nowrap}

.faq details{border-bottom:1px solid var(--line);padding:0}
.faq details:first-of-type{border-top:1px solid var(--line)}
.faq summary{
  list-style:none;cursor:pointer;padding:15px 34px 15px 0;font-weight:570;font-size:1rem;
  letter-spacing:-.014em;position:relative;
}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{
  content:"";position:absolute;right:6px;top:50%;width:9px;height:9px;margin-top:-6px;
  border-right:1.8px solid var(--ink-3);border-bottom:1.8px solid var(--ink-3);
  transform:rotate(45deg);transition:transform .18s ease;
}
.faq details[open] summary::after{transform:rotate(225deg);margin-top:-2px}
.faq summary:hover{color:var(--accent)}
.faq .ans{padding:0 0 17px;color:var(--ink-2);font-size:.965rem}
.faq .ans p:last-child{margin-bottom:0}

/* --- category cards --- */
.cats{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:0}
.cat{
  display:block;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  padding:17px 18px;box-shadow:var(--sh-1);color:var(--ink);
  transition:transform .16s ease,box-shadow .16s ease,border-color .16s ease;
}
.cat:hover{text-decoration:none;transform:translateY(-2px);box-shadow:var(--sh-2);border-color:var(--accent-line)}
.cat svg{width:19px;height:19px;color:var(--accent);margin-bottom:9px}
.cat h3{font-size:.985rem;font-weight:600;margin-bottom:3px}
.cat p{margin:0;font-size:.85rem;color:var(--ink-3);line-height:1.45}

/* --- footer --- */
.site-foot{margin-top:72px;border-top:1px solid var(--line);background:var(--surface-2);padding:38px 0 26px;font-size:.875rem}
.foot-grid{display:grid;grid-template-columns:1.6fr repeat(3,1fr);gap:32px}
.foot-grid h3{font-size:.76rem;font-weight:640;letter-spacing:.08em;text-transform:uppercase;color:var(--ink-3);margin-bottom:11px}
.foot-grid ul{list-style:none;margin:0;padding:0;display:grid;gap:7px}
.foot-grid a{color:var(--ink-2)}
.foot-grid a:hover{color:var(--accent)}
.foot-about p{color:var(--ink-3);font-size:.86rem;max-width:34ch;margin:10px 0 0}
.foot-base{
  margin-top:30px;padding-top:18px;border-top:1px solid var(--line);
  display:flex;flex-wrap:wrap;gap:8px 20px;justify-content:space-between;color:var(--ink-3);font-size:.82rem;
}

/* ==========================================================================
   Responsive — 1180 / 1080 / 940 / 820 / 720 / 600 / 480 / 380
   Every grid track below uses minmax(0,1fr) so children can shrink.
   ========================================================================== */

@media (max-width:1180px){
  .wrap{padding-inline:20px}
  .body-layout{gap:40px}
}

@media (max-width:1080px){
  .body-layout{grid-template-columns:minmax(0,1fr);gap:0}
  .toc{position:static;margin-bottom:34px;border:1px solid var(--line);border-radius:var(--r-lg);
       background:var(--surface);padding:15px 17px;box-shadow:var(--sh-1)}
  .toc ol{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0}
  .toc a{border-left:0;padding-left:0}
  .toc a.on{background:none;padding-left:0}
  .article{max-width:none}
}

@media (max-width:940px){
  .calc-grid{grid-template-columns:minmax(0,1fr)}
  .results{border-left:0;border-top:1px solid var(--line-soft)}
  .strip{grid-template-columns:repeat(2,minmax(0,1fr))}
  .cats{grid-template-columns:repeat(2,minmax(0,1fr))}
  .posts,.posts.wide{grid-template-columns:repeat(2,minmax(0,1fr))}
  .foot-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:28px}
  .units{grid-template-columns:repeat(2,minmax(0,1fr))}
}

/* ---------- tablet and phone ---------- */
@media (max-width:820px){
  .feature{grid-template-columns:minmax(0,1fr)}
}

@media (max-width:720px){
  body{font-size:16px}
  .wrap{padding-inline:16px}

  /* header */
  .head-in{height:58px;gap:12px}
  .burger{display:flex}
  .nav{
    position:fixed;inset:58px 0 auto;background:var(--surface);border-bottom:1px solid var(--line);
    flex-direction:column;align-items:stretch;padding:8px 16px 18px;gap:0;box-shadow:var(--sh-2);
    display:none;max-height:calc(100dvh - 58px);overflow-y:auto;overscroll-behavior:contain;
  }
  .nav[data-open="true"]{display:flex}
  .nav a,.nav .has-sub>button{
    font-size:1rem;padding:13px 12px;width:100%;text-align:left;min-height:46px;
    border-radius:var(--r-md);
  }
  .nav>a+a,.nav .has-sub+a,.nav a+.has-sub{border-top:1px solid var(--line-soft)}
  .nav .has-sub{width:100%}
  .nav .has-sub>button{justify-content:space-between}
  .submenu{position:static;box-shadow:none;border:0;border-radius:0;padding:0 0 8px 10px;min-width:0;width:100%}
  .submenu a{padding:11px 10px;min-height:44px}

  /* hero */
  .hero{padding:30px 0 6px}
  .hero h1{max-width:none}
  .trust{
    justify-content:flex-start;text-align:left;gap:9px 0;margin-top:1.2rem;
    display:grid;grid-template-columns:repeat(2,minmax(0,1fr));
  }
  .trust li{align-items:flex-start;font-size:.83rem;line-height:1.35}
  .trust svg{margin-top:2px}

  /* calculator */
  .calc{border-radius:var(--r-lg);margin-top:22px}
  .pane,.results{padding:16px}
  .shapes{padding:12px 16px;gap:5px}
  .shape-btn{min-width:66px;padding:8px 6px 6px;font-size:.7rem}
  .shape-btn svg{width:23px;height:23px}
  .pane-head{flex-direction:column;align-items:flex-start;gap:2px;margin-bottom:14px}
  .row-2{grid-template-columns:repeat(2,minmax(0,1fr))}
  .pane-actions{gap:7px}
  .pane-actions .btn{flex:1 1 auto;min-height:44px}
  .pane-actions .btn-primary{flex:1 1 100%}
  .diagram{padding:12px}
  .diagram svg{max-height:150px}

  /* 16px stops iOS Safari zooming the page when a field is focused */
  .control input,.control select,.searchform input{font-size:16px}
  .control input{padding:13px 13px;font-size:16px}
  .control select{flex:0 0 84px !important;width:84px !important;min-width:84px;max-width:84px;padding:0 24px 0 10px}
  #cfc-currency{flex:0 0 58px !important;width:58px !important;min-width:58px;max-width:58px}

  /* results */
  .headline{padding:15px 16px}
  .units li{padding:9px 11px}
  details.card>summary{padding:13px 14px;min-height:46px}

  /* content */
  .toc ol{grid-template-columns:minmax(0,1fr)}
  .toc a{padding:7px 0;min-height:34px}
  .article section{margin-bottom:40px}
  .formula{font-size:.84rem;padding:11px 13px}
  .worked{padding:15px 16px}
  .callout{padding:13px 15px}
  .faq summary{padding-right:30px}

  /* cards and footer */
  .strip{grid-template-columns:repeat(2,minmax(0,1fr))}
  .cats{grid-template-columns:minmax(0,1fr)}
  .posts,.posts.wide{grid-template-columns:minmax(0,1fr)}
  .foot-grid{grid-template-columns:minmax(0,1fr);gap:24px}
  .site-foot{margin-top:52px;padding:30px 0 24px}
  .foot-base{flex-direction:column;gap:6px}

  /* blog */
  .page-hero{padding:26px 0 20px}
  .cat-rail{padding-bottom:16px;margin-bottom:26px}
  .cat-rail ul{flex-wrap:nowrap;overflow-x:auto;-webkit-overflow-scrolling:touch;
               padding-bottom:6px;scroll-snap-type:x proximity}
  .cat-rail li{flex:none;scroll-snap-align:start}
  .cat-rail a{min-height:40px}
  .postnav{grid-template-columns:minmax(0,1fr)}
  .postnav .next{text-align:left}
  .tool-promo{flex-wrap:wrap}
  .tool-promo .btn{width:100%;min-height:46px}
  .author-box{flex-direction:column;gap:12px}

  /* comfortable tap targets everywhere */
  .btn{min-height:44px;padding-inline:16px}
  .pager .page-numbers{min-width:42px;height:42px}
}

@media (max-width:600px){
  .units{grid-template-columns:repeat(2,minmax(0,1fr))}
  .headline .v{font-size:clamp(1.8rem,1.2rem + 4vw,2.4rem)}
  .items li{flex-wrap:wrap;gap:6px 10px}
  .items .nm{flex:1 1 100%}
  .total-bar{flex-direction:column;align-items:flex-start;gap:4px}
}

@media (max-width:480px){
  .wrap{padding-inline:14px}
  .row-2{grid-template-columns:minmax(0,1fr)}
  .strip{grid-template-columns:minmax(0,1fr)}
  .trust{grid-template-columns:minmax(0,1fr)}
  .brand img{width:112px;height:31px}
  .pane,.results{padding:14px}
  .shapes{padding:10px 14px}
  .units{grid-template-columns:minmax(0,1fr)}
  .article h2{font-size:1.35rem}
  .entry h2{font-size:1.3rem}
  .feature-body{padding:18px}
  .pane-actions .btn{flex:1 1 100%}
}

@media (max-width:380px){
  .wrap{padding-inline:12px}
  .brand img{width:100px;height:28px}
  .control select{flex:0 0 76px !important;width:76px !important;min-width:76px;max-width:76px;font-size:15px;padding:0 22px 0 9px}
  .shape-btn{min-width:60px}
  .headline{padding:13px 14px}
}

/* Short landscape phones: stop the sticky header eating the viewport. */
@media (max-height:520px) and (orientation:landscape){
  .site-head{position:static}
  .nav{position:static;max-height:none}
  html{scroll-padding-top:12px}
  .article section{scroll-margin-top:12px}
}

@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{animation-duration:.001ms !important;transition-duration:.001ms !important;scroll-behavior:auto !important}
}

@media print{
  .site-head,.site-foot,.shapes,.pane-actions,.toc,.addons,.diagram,.ocfc-top{display:none !important}
  .calc{box-shadow:none;border:1px solid #999}
  .calc-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
  body{background:#fff}
}

/* ==========================================================================
   Site pages — blog index, category archives, single posts, static pages
   ========================================================================== */

.page-hero{padding:46px 0 30px;border-bottom:1px solid var(--line-soft);margin-bottom:40px}
.page-hero.tight{padding-bottom:22px;margin-bottom:32px}
.page-hero h1{max-width:22ch}
.page-hero .lede{max-width:62ch;margin-top:.8rem}

.crumbs{display:flex;flex-wrap:wrap;align-items:center;gap:6px;margin:0 0 14px;padding:0;list-style:none;font-size:.82rem;color:var(--ink-3)}
.crumbs li{display:flex;align-items:center;gap:6px}
.crumbs li+li::before{content:"";width:4px;height:4px;border-right:1.4px solid var(--ink-3);border-top:1.4px solid var(--ink-3);transform:rotate(45deg);display:block}
.crumbs a{color:var(--ink-3)}
.crumbs a:hover{color:var(--accent)}
.crumbs [aria-current]{color:var(--ink-2)}

.meta{display:flex;flex-wrap:wrap;align-items:center;gap:6px 14px;font-size:.845rem;color:var(--ink-3);margin:0}
.meta .tag{
  display:inline-block;background:var(--accent-soft);color:var(--accent-dark);border:1px solid var(--accent-line);
  border-radius:999px;padding:2px 10px;font-size:.76rem;font-weight:570;letter-spacing:-.005em;
}
.meta .tag:hover{text-decoration:none;background:#E3E7FC}
.meta time{font-variant-numeric:tabular-nums}

/* --- post grid --- */
.posts{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px;margin:0;padding:0;list-style:none}
.posts.wide{grid-template-columns:repeat(2,minmax(0,1fr))}
.pcard{
  display:flex;flex-direction:column;background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r-lg);box-shadow:var(--sh-1);overflow:hidden;height:100%;
  transition:transform .16s ease,box-shadow .16s ease,border-color .16s ease;
}
.pcard:hover{transform:translateY(-2px);box-shadow:var(--sh-2);border-color:var(--accent-line)}
.pcard .thumb{display:block;aspect-ratio:16/9;background:var(--surface-3);overflow:hidden}
.pcard .thumb img{width:100%;height:100%;object-fit:cover}
.pcard .in{padding:15px 17px 17px;display:flex;flex-direction:column;gap:7px;flex:1;min-width:0}
.pcard h2,.pcard h3{font-size:1.02rem;font-weight:600;letter-spacing:-.018em;line-height:1.3}
.pcard h2 a,.pcard h3 a{color:var(--ink)}
.pcard h2 a:hover,.pcard h3 a:hover{color:var(--accent);text-decoration:none}
.pcard p{margin:0;font-size:.885rem;color:var(--ink-2);line-height:1.5}
.pcard .meta{margin-top:auto;padding-top:4px}

/* --- article body (what the editor outputs) --- */
.entry{max-width:74ch}
.entry>*:first-child{margin-top:0}
.entry p{margin:0 0 1.15em}
.entry h2{font-size:clamp(1.38rem,1.2rem + .8vw,1.75rem);margin:2.1em 0 .55em;letter-spacing:-.026em;scroll-margin-top:92px}
.entry h3{font-size:1.16rem;margin:1.8em 0 .5em;scroll-margin-top:92px}
.entry h4{font-size:1rem;margin:1.5em 0 .4em}
.entry ul,.entry ol{margin:0 0 1.15em;padding-left:1.3em}
.entry li{margin-bottom:.45em}
.entry li::marker{color:var(--ink-3)}
.entry a{text-decoration:underline;text-underline-offset:2px;text-decoration-thickness:1px;text-decoration-color:var(--accent-line)}
.entry a:hover{text-decoration-color:var(--accent)}
.entry strong{font-weight:620}
.entry blockquote{
  margin:0 0 1.3em;padding:2px 0 2px 20px;border-left:3px solid var(--accent);
  color:var(--ink-2);font-size:1.04rem;
}
.entry blockquote p:last-child{margin-bottom:0}
.entry figure{margin:0 0 1.5em}
.entry img{border-radius:var(--r-lg);border:1px solid var(--line-soft);height:auto}
.entry figcaption{margin-top:8px;font-size:.83rem;color:var(--ink-3);text-align:center}
.entry code{
  font-family:var(--mono);font-size:.88em;background:var(--surface-3);
  padding:.12em .38em;border-radius:5px;
}
.entry pre{
  background:var(--surface-2);border:1px solid var(--line-soft);border-radius:var(--r-md);
  padding:14px 16px;overflow-x:auto;font-family:var(--mono);font-size:.86rem;margin:0 0 1.3em;
}
.entry pre code{background:none;padding:0}
.entry hr{border:0;border-top:1px solid var(--line);margin:2.4em 0}
.entry table{margin:0}
.entry .wp-block-table{overflow-x:auto;margin:0 0 1.3em;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--surface);box-shadow:var(--sh-1)}
.entry .wp-block-table table{min-width:420px}
.entry .wp-block-button__link{
  display:inline-block;background:var(--accent);color:#fff;border-radius:999px;
  padding:10px 20px;font-weight:560;font-size:.9rem;text-decoration:none;
}
.entry .alignleft{float:left;margin:.3em 1.5em 1em 0}
.entry .alignright{float:right;margin:.3em 0 1em 1.5em}
.entry .aligncenter{margin-inline:auto;display:block}

/* --- a promo for the calculator, dropped into posts --- */
.tool-promo{
  display:flex;align-items:center;gap:16px;background:var(--surface);border:1px solid var(--line);
  border-left:3px solid var(--accent);border-radius:var(--r-lg);padding:16px 19px;margin:2.2em 0;
  box-shadow:var(--sh-1);
}
.tool-promo svg{width:28px;height:28px;color:var(--accent);flex:none}
.tool-promo div{flex:1;min-width:0}
.tool-promo h3{font-size:.98rem;font-weight:600;margin-bottom:2px}
.tool-promo p{margin:0;font-size:.865rem;color:var(--ink-3)}
.tool-promo .btn{flex:none}
@media (max-width:620px){.tool-promo{flex-wrap:wrap}.tool-promo .btn{width:100%}}

/* --- author + related --- */
.author-box{
  display:flex;gap:15px;align-items:flex-start;background:var(--surface-2);border:1px solid var(--line-soft);
  border-radius:var(--r-lg);padding:17px 19px;margin:2.6em 0 0;
}
.author-box img{width:48px;height:48px;border-radius:50%;flex:none}
.author-box h3{font-size:.95rem;font-weight:600;margin-bottom:3px}
.author-box p{margin:0;font-size:.87rem;color:var(--ink-2);line-height:1.5}

.related{margin-top:56px;padding-top:34px;border-top:1px solid var(--line)}
.related h2{font-size:1.28rem;margin-bottom:16px}

/* --- pagination --- */
.pager{display:flex;flex-wrap:wrap;gap:6px;justify-content:center;margin:44px 0 0}
.pager .page-numbers{
  display:inline-flex;align-items:center;justify-content:center;min-width:38px;height:38px;padding:0 12px;
  border:1px solid var(--line);border-radius:var(--r-md);background:var(--surface);box-shadow:var(--sh-1);
  font-size:.89rem;font-weight:540;color:var(--ink-2);font-variant-numeric:tabular-nums;
}
.pager a.page-numbers:hover{background:var(--surface-2);color:var(--ink);text-decoration:none}
.pager .page-numbers.current{background:var(--accent);border-color:var(--accent);color:#fff}
.pager .dots{border-color:transparent;box-shadow:none;background:none}

/* --- post navigation --- */
.postnav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:44px}
.postnav a{
  display:block;background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);
  padding:14px 17px;box-shadow:var(--sh-1);color:var(--ink);
}
.postnav a:hover{text-decoration:none;border-color:var(--accent-line);box-shadow:var(--sh-2)}
.postnav .k{display:block;font-size:.75rem;font-weight:620;letter-spacing:.07em;text-transform:uppercase;color:var(--ink-3);margin-bottom:4px}
.postnav .t{font-size:.93rem;font-weight:560;line-height:1.35}
.postnav .next{text-align:right}
@media (max-width:620px){.postnav{grid-template-columns:minmax(0,1fr)}.postnav .next{text-align:left}}

/* --- search + 404 --- */
.searchform{display:flex;gap:8px;max-width:440px;margin:0}
.searchform .control{flex:1}
.blank{text-align:center;padding:60px 0 20px;max-width:52ch;margin-inline:auto}
.blank .big{font-size:clamp(3rem,2rem + 4vw,4.6rem);font-weight:660;letter-spacing:-.045em;color:var(--accent);line-height:1;margin-bottom:12px;font-variant-numeric:tabular-nums}
.blank .searchform{margin:22px auto 0}

/* --- category rail on archives --- */
.cat-rail{display:flex;flex-wrap:wrap;gap:7px;margin:0 0 34px;padding:0;list-style:none}
.cat-rail a{
  display:inline-block;padding:7px 14px;border:1px solid var(--line);border-radius:999px;
  background:var(--surface);box-shadow:var(--sh-1);font-size:.855rem;font-weight:520;color:var(--ink-2);
}
.cat-rail a:hover{background:var(--surface-2);color:var(--ink);text-decoration:none}
.cat-rail a[aria-current]{background:var(--accent);border-color:var(--accent);color:#fff}

.page-body{padding-bottom:20px}

@media (max-width:940px){.posts,.posts.wide{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media (max-width:640px){.posts,.posts.wide{grid-template-columns:minmax(0,1fr)}.page-hero{padding:30px 0 22px}}