/* ==========================================================================
   CITe — Natural Ventilation Assessment Tool
   Static build. No external requests: fonts, colours and charts are local.
   ========================================================================== */

:root {
  --bg:        #0B0F14;
  --panel:     #131A22;
  --panel-2:   #18212B;
  --line:      #22303C;
  --line-soft: #1B2530;
  --ink:       #E6EDF3;
  --ink-dim:   #9FB0BF;
  --ink-faint: #6C7F8F;
  --accent:    #4CC2E0;
  --accent-dk: #1E7C93;

  /* Performance ramp — identical to the original tool */
  --b0:  #F7696B; --b1:  #F87F6F; --b2:  #F99774; --b3:  #FAAE78; --b4:  #FBC67D;
  --b5:  #FCDE80; --b6:  #F0E683; --b7:  #D4DE81; --b8:  #B8D680; --b9:  #9BCE7F;

  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SFMono-Regular", "Cascadia Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --rail: 300px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 15px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); }

/* ---------- Masthead ---------- */

.masthead {
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, #101822 0%, #0B0F14 100%);
  position: sticky;
  top: 0;
  z-index: 20;
}

.masthead-inner {
  display: flex;
  align-items: center;
  gap: 24px;
  padding: 0 22px;
  min-height: 58px;
  flex-wrap: wrap;
}

.wordmark {
  display: flex;
  align-items: baseline;
  gap: 10px;
  text-decoration: none;
  color: var(--ink);
  padding: 10px 0;
}

.wordmark b {
  font-size: 19px;
  font-weight: 700;
  letter-spacing: .02em;
}

.wordmark span {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

.tabs {
  display: flex;
  gap: 2px;
  margin-left: auto;
  flex-wrap: wrap;
}

.tabs a {
  display: block;
  padding: 8px 14px;
  border-radius: 7px;
  font-size: 13.5px;
  color: var(--ink-dim);
  text-decoration: none;
  border: 1px solid transparent;
  transition: background .15s, color .15s, border-color .15s;
}

.tabs a:hover { background: var(--panel-2); color: var(--ink); }

.tabs a[aria-current="page"] {
  background: rgba(76, 194, 224, .10);
  border-color: rgba(76, 194, 224, .35);
  color: var(--accent);
}

/* ---------- Shell ---------- */

.shell {
  display: grid;
  grid-template-columns: var(--rail) minmax(0, 1fr);
  gap: 0;
  align-items: start;
}

.rail {
  border-right: 1px solid var(--line);
  padding: 18px 18px 40px;
  position: sticky;
  top: 58px;
  max-height: calc(100vh - 58px);
  overflow-y: auto;
}

.rail h2 {
  font-size: 11px;
  letter-spacing: .17em;
  text-transform: uppercase;
  color: var(--ink-faint);
  font-family: var(--mono);
  font-weight: 500;
  margin: 0 0 14px;
}

.rail-group {
  border-top: 1px solid var(--line-soft);
  padding-top: 14px;
  margin-top: 16px;
}

.rail-group:first-of-type { border-top: 0; margin-top: 0; padding-top: 0; }

.rail-group > h3 {
  font-size: 10.5px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  font-family: var(--mono);
  font-weight: 500;
  margin: 0 0 10px;
}

.field { margin-bottom: 12px; }

.field.pair { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }

label {
  display: block;
  font-size: 11.5px;
  color: var(--ink-dim);
  margin-bottom: 5px;
}

select {
  width: 100%;
  appearance: none;
  background: var(--panel-2);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 8px 26px 8px 10px;
  font-size: 13.5px;
  font-family: var(--sans);
  cursor: pointer;
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M1 1l4 4 4-4' stroke='%239FB0BF' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 9px center;
}

select:hover { border-color: #33475a; }
select:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
select:disabled { opacity: .38; cursor: not-allowed; }

/* ---------- Main ---------- */

.main { padding: 22px 24px 60px; min-width: 0; }

.headline {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
  border-bottom: 1px solid var(--line);
  padding-bottom: 16px;
  margin-bottom: 20px;
}

.headline h1 {
  margin: 0;
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -.01em;
}

.headline p {
  margin: 4px 0 0;
  font-size: 13px;
  color: var(--ink-dim);
  max-width: 62ch;
}

.index-card {
  text-align: right;
  white-space: nowrap;
}

.index-card .k {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

.index-card .v {
  font-family: var(--mono);
  font-size: 40px;
  font-weight: 600;
  line-height: 1.05;
  letter-spacing: -.02em;
  font-variant-numeric: tabular-nums;
}

.index-card .v small { font-size: 18px; color: var(--ink-faint); margin-left: 2px; }

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 340px;
  gap: 22px;
  align-items: start;
}

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
}

.card > header {
  padding: 10px 14px;
  border-bottom: 1px solid var(--line-soft);
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  display: flex;
  justify-content: space-between;
  gap: 10px;
}

.card > .body { padding: 14px; }

/* ---------- Calendar grid (the signature) ---------- */

.grid-scroll { overflow-x: auto; }

table.calendar {
  border-collapse: separate;
  border-spacing: 2px;
  width: 100%;
  font-family: var(--mono);
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

table.calendar th {
  font-weight: 500;
  font-size: 10px;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  padding: 4px 2px;
  text-align: center;
}

table.calendar th.day-h { width: 26px; text-align: right; padding-right: 6px; }

table.calendar td.day-n {
  color: var(--ink-faint);
  text-align: right;
  padding-right: 6px;
  font-size: 10px;
}

table.calendar td.cell {
  text-align: center;
  padding: 3px 2px;
  border-radius: 3px;
  color: #10161C;
  font-weight: 600;
  min-width: 40px;
  cursor: default;
}

table.calendar td.cell.empty {
  background: transparent;
  color: #2B3946;
  font-weight: 400;
}

table.calendar td.cell:hover { outline: 1.5px solid var(--ink); outline-offset: -1px; }

/* ---------- Donut ---------- */

.donut-wrap { display: flex; flex-direction: column; align-items: center; gap: 10px; }

.legend {
  width: 100%;
  display: grid;
  gap: 3px;
  font-family: var(--mono);
  font-size: 10.5px;
  font-variant-numeric: tabular-nums;
}

.legend-row {
  display: grid;
  grid-template-columns: 12px 1fr auto auto;
  gap: 8px;
  align-items: center;
  color: var(--ink-dim);
  padding: 1px 0;
}

.legend-row i { width: 12px; height: 12px; border-radius: 3px; display: block; }
.legend-row .pct { color: var(--ink); }
.legend-row .n { color: var(--ink-faint); width: 34px; text-align: right; }

/* ---------- Schematic ---------- */

.schematic { width: 100%; display: block; border-radius: 8px; background: var(--panel-2); }
img.schematic { object-fit: contain; }

.note {
  font-size: 11.5px;
  color: var(--ink-faint);
  margin: 8px 0 0;
  line-height: 1.5;
}

.side-stack { display: grid; gap: 22px; }

/* ---------- Introduction page ---------- */

.doc { max-width: 1180px; margin: 0 auto; padding: 30px 24px 70px; }

.hero {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 34px;
  align-items: center;
  padding-bottom: 30px;
  border-bottom: 1px solid var(--line);
}

.hero h1 {
  font-size: clamp(26px, 3.6vw, 40px);
  line-height: 1.12;
  letter-spacing: -.02em;
  margin: 0 0 14px;
  font-weight: 650;
}

.hero .eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 12px;
}

.hero p { color: var(--ink-dim); margin: 0 0 10px; }

.hero-figure {
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow: hidden;
  background: var(--panel);
  min-height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.hero-figure img { width: 100%; height: auto; display: block; }

.doc-section { padding-top: 30px; }

.doc-section h2 {
  font-size: 17px;
  margin: 0 0 12px;
  font-weight: 600;
}

.doc-section ul { margin: 0; padding-left: 20px; color: var(--ink-dim); }
.doc-section li { margin-bottom: 9px; }
.doc-section li strong { color: var(--ink); }

.cols-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 34px; }

.authors { list-style: none; padding: 0; margin: 0; }
.authors li {
  padding: 7px 0;
  border-bottom: 1px solid var(--line-soft);
  color: var(--ink);
}

.colophon {
  margin-top: 40px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  display: flex;
  align-items: center;
  gap: 14px;
  color: var(--ink-faint);
  font-size: 12.5px;
  flex-wrap: wrap;
}

.colophon img { height: 38px; width: auto; }

/* ---------- Utility ---------- */

.msg {
  padding: 14px;
  border: 1px dashed var(--line);
  border-radius: 8px;
  color: var(--ink-dim);
  font-size: 13px;
}

[hidden] { display: none !important; }

@media (max-width: 1080px) {
  .layout { grid-template-columns: 1fr; }
  .hero, .cols-2 { grid-template-columns: 1fr; }
}

@media (max-width: 820px) {
  .shell { grid-template-columns: 1fr; }
  .rail {
    position: static;
    max-height: none;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }
  .masthead { position: static; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}