:root {
  color-scheme: light;
  --ink: #17201d;
  --muted: #586761;
  --line: #cbd8d3;
  --paper: #f8faf7;
  --panel: #ffffff;
  --band: #eef4f1;
  --teal: #0d766f;
  --teal-deep: #0a4f4a;
  --amber: #b66d12;
  --blue: #315f97;
  --red: #a84732;
  --shadow: 0 20px 50px rgba(23, 32, 29, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.5;
}

a {
  color: inherit;
}

code,
pre,
select,
input,
textarea {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 14px clamp(16px, 4vw, 54px);
  border-bottom: 1px solid rgba(23, 32, 29, 0.12);
  background: rgba(248, 250, 247, 0.94);
  backdrop-filter: blur(12px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 1.16rem;
  font-weight: 750;
  letter-spacing: 0;
  text-decoration: none;
}

.brand-mark {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  border: 2px solid var(--teal);
  background:
    linear-gradient(90deg, transparent 46%, var(--teal) 47%, var(--teal) 53%, transparent 54%),
    linear-gradient(0deg, transparent 46%, var(--amber) 47%, var(--amber) 53%, transparent 54%);
}

/* The nav was `justify-content: flex-end` at 0.94rem in the muted grey, so on a
   wide screen five links crowded into the right corner as small low-contrast
   text with no hit area and no indication of which page you were on. These are
   the site's only navigation; they need to read as buttons you can aim at. */
nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 4px;
  font-size: 1rem;
}

nav a {
  border-radius: 8px;
  color: var(--ink, #1d2b2b);
  display: inline-block;
  font-weight: 600;
  padding: 9px 14px;
  text-decoration: none;
  transition: background-color 120ms ease, color 120ms ease;
  white-space: nowrap;
}

nav a:hover,
nav a:focus-visible {
  background: rgba(15, 118, 110, 0.10);
  color: var(--teal-deep);
}

/* Where am I. Without this every page's nav looked identical. */
nav a[aria-current="page"] {
  background: rgba(15, 118, 110, 0.14);
  box-shadow: inset 0 -2px 0 var(--teal);
  color: var(--teal-deep);
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 0.75fr) minmax(360px, 1.25fr);
  align-items: start;
  gap: clamp(26px, 5vw, 64px);
  padding: clamp(34px, 6vw, 76px) clamp(16px, 5vw, 72px);
}

.page-hero {
  max-width: 960px;
  padding: clamp(42px, 7vw, 86px) clamp(16px, 5vw, 72px) clamp(22px, 4vw, 44px);
}

.page-hero p:last-child {
  max-width: 780px;
  font-size: clamp(1rem, 1.7vw, 1.22rem);
}

.intro {
  position: sticky;
  top: 92px;
  max-width: 620px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--teal-deep);
  font-size: 0.78rem;
  font-weight: 850;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  overflow-wrap: anywhere;
}

h1 {
  margin: 0;
  font-size: clamp(2rem, 4.6vw, 3.8rem);
  line-height: 1.02;
  letter-spacing: 0;
}

h2 {
  margin: 0 0 14px;
  font-size: clamp(1.45rem, 2.5vw, 2.2rem);
  line-height: 1.08;
  letter-spacing: 0;
}

p {
  color: var(--muted);
}

.notation-example {
  display: inline-flex;
  margin-top: 24px;
  min-height: 48px;
  align-items: center;
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: 0 1px 0 rgba(23, 32, 29, 0.04);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-weight: 800;
}

.tool-card {
  display: grid;
  gap: 16px;
  align-content: start;
  width: 100%;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fbfdfa;
  box-shadow: var(--shadow);
  overflow: visible;
}

.panel-head,
.compare-head {
  display: flex;
  align-items: end;
  justify-content: center;
  gap: 18px;
  padding: 0 0 5px;
  border-bottom: 0;
  text-align: center;
}

.panel-head h2,
.compare-head h2 {
  margin: 0;
  font-size: clamp(1.45rem, 2.5vw, 2.2rem);
  line-height: 1.08;
}

.panel-head h2,
.panel-head p,
.panel-head .eyebrow,
.compare-head h2,
.compare-head p,
.compare-head .eyebrow {
  margin: 0;
}

.panel-head p,
.compare-head p {
  max-width: 360px;
  color: var(--muted);
  font-size: 0.92rem;
  text-align: right;
}

form {
  display: grid;
  gap: 8px;
}

#calculator-form {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.field-row {
  display: grid;
  grid-template-columns: 1fr;
  align-items: start;
  gap: 9px;
  padding: 0;
  border-bottom: 0;
}

.field-row:nth-child(odd) {
  border-right: 0;
}

.field-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 38px;
  justify-self: start;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
}

label {
  color: var(--ink);
  font-weight: 750;
}

.info-button {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
  border: 0;
  border-radius: 0;
  background: transparent;
  color: var(--muted);
  cursor: help;
  font-family: inherit;
  font-size: 0.82rem;
  font-weight: 700;
  line-height: 1;
  padding: 0;
  vertical-align: middle;
}

.info-button::after {
  position: absolute;
  left: 50%;
  bottom: calc(100% + 10px);
  z-index: 20;
  width: min(280px, 72vw);
  transform: translateX(-50%);
  border-radius: 8px;
  background: var(--ink);
  color: #f7fbf9;
  content: attr(data-tooltip);
  font-size: 0.82rem;
  font-weight: 600;
  line-height: 1.35;
  opacity: 0;
  padding: 10px 11px;
  pointer-events: none;
  transition: opacity 0.15s ease;
}

label:hover + .info-button::after,
.info-button:hover::after,
.info-button:focus-visible::after {
  opacity: 1;
}

label:hover + .info-button,
.info-button:hover,
.info-button:focus-visible {
  color: var(--teal-deep);
}

.input-pair {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(170px, 0.45fr);
  gap: 8px;
}

input,
select,
textarea {
  width: 100%;
  min-height: 38px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #fff;
  color: var(--ink);
  font-size: 0.92rem;
  padding: 9px 10px;
}

textarea {
  resize: vertical;
}

input::placeholder,
textarea::placeholder {
  color: rgba(88, 103, 97, 0.34);
  opacity: 1;
}

input:focus,
select:focus,
textarea:focus,
button:focus-visible {
  outline: 3px solid rgba(13, 118, 111, 0.18);
  border-color: var(--teal);
}

.hint {
  margin: 0;
  color: var(--muted);
  font-size: 0.82rem;
}

.inline-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}

.input-section {
  grid-column: 1 / -1;
  display: grid;
  gap: 12px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.input-section h3 {
  grid-column: 1 / -1;
  margin: 0;
  color: var(--teal-deep);
  font-size: 0.76rem;
  font-weight: 850;
  text-transform: uppercase;
}

.required-inputs {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

/* The temperature block is no longer "optional extras" — for heat and cooling it
   is where the answer comes from, so it reads as a required part of the form. */
.temperature-section {
  border-left: 3px solid var(--teal);
  padding-left: 14px;
}

.section-note {
  color: var(--muted);
  font-size: 0.9rem;
  margin: -2px 0 10px;
  max-width: 52ch;
}

.advanced-options {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-color: var(--line);
  background: #fbfdfa;
}

.advanced-options h3 {
  color: var(--muted);
}

.checkline {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 650;
}

.checkline input {
  width: 18px;
  min-height: 18px;
}

button,
.primary-link {
  min-height: 38px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  font-weight: 750;
  padding: 8px 12px;
  text-decoration: none;
}

.primary-button {
  border-color: var(--teal-deep);
  background: var(--teal-deep);
  color: #fff;
}

.ghost-button:hover,
.example-grid button:hover {
  border-color: var(--teal);
  color: var(--teal-deep);
}

.form-actions {
  grid-column: 1 / -1;
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  padding: 8px 0 0;
}

.results {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.simple-result {
  grid-template-columns: 1fr;
}

.results > div {
  min-height: auto;
  padding: 0;
  background: transparent;
  color: var(--ink);
}

.result-label {
  display: block;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 850;
  margin-bottom: 8px;
  text-transform: uppercase;
}

.results strong {
  display: block;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: clamp(0.98rem, 2vw, 1.25rem);
  line-height: 1.25;
}

.conversion-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1px;
  background: var(--line);
}

.conversion-card {
  display: grid;
  gap: 4px;
  min-height: 84px;
  padding: 14px;
  background: var(--panel);
}

.conversion-card span {
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 800;
  text-transform: uppercase;
}

.conversion-card strong {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.tool-section {
  padding: 0 clamp(16px, 5vw, 72px) clamp(40px, 7vw, 76px);
}

.compare-panel {
  display: grid;
  gap: 16px;
}

.compare-rows {
  display: grid;
  gap: 14px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.compare-row {
  display: grid;
  grid-template-columns: 32px minmax(190px, 1fr) minmax(100px, 0.42fr) minmax(170px, 0.65fr) minmax(110px, 0.45fr);
  align-items: end;
  gap: 12px;
}

.compare-side-label {
  display: grid;
  width: 28px;
  height: 28px;
  place-items: center;
  align-self: center;
  margin-bottom: 5px;
  border-radius: 50%;
  background: var(--ink);
  color: #fff;
  font-size: 0.85rem;
  font-weight: 850;
}

.compare-row input,
.compare-row select {
  min-height: 38px;
  font-size: 0.92rem;
}

.compare-result {
  display: grid;
  gap: 12px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.compare-answers {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  padding: 14px;
  border: 1px solid rgba(13, 118, 111, 0.24);
  border-radius: 8px;
  background: #eef8f5;
}

.calculator-result {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.answer-item {
  display: grid;
  gap: 6px;
  min-width: 0;
}

.answer-item strong {
  color: var(--teal-deep);
  font-family: inherit;
  font-size: clamp(0.98rem, 2vw, 1.25rem);
  font-weight: 600;
  line-height: 1.25;
}

.result-wide {
  grid-column: 1 / -1;
}

/* The re-derivation line is arithmetic, so it is set in a monospace face and
   allowed to wrap rather than overflow on a phone. It reads lighter than the
   notation above it because it is the working, not the result. */
.verify-line {
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  font-size: clamp(0.82rem, 1.6vw, 0.95rem) !important;
  font-weight: 500 !important;
  overflow-wrap: anywhere;
  opacity: 0.85;
}

.compare-bars {
  display: grid;
  gap: 12px;
}

.bar-row {
  display: grid;
  grid-template-columns: minmax(150px, 0.85fr) minmax(180px, 1fr) minmax(92px, 0.4fr);
  align-items: center;
  gap: 12px;
}

.bar-meta {
  display: grid;
  gap: 2px;
  min-width: 0;
}

.bar-meta span {
  color: var(--teal-deep);
  font-size: 0.72rem;
  font-weight: 900;
}

.bar-meta strong,
.bar-meta em,
.bar-value {
  overflow-wrap: anywhere;
}

.bar-meta strong {
  font-size: 0.92rem;
}

.bar-meta em {
  color: var(--muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.78rem;
  font-style: normal;
}

.bar-track {
  height: 14px;
  overflow: hidden;
  border-radius: 999px;
  background: #e2ebe7;
}

.bar-fill {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--amber), var(--teal));
}

.bar-value {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.86rem;
  text-align: right;
}

.section-band,
.section,
.paper-strip {
  padding: clamp(40px, 7vw, 76px) clamp(16px, 5vw, 72px);
}

.compact-section {
  padding-block: clamp(28px, 5vw, 48px);
}

.section-band {
  border-block: 1px solid rgba(23, 32, 29, 0.08);
  background: var(--band);
}

.content-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(24px, 5vw, 56px);
  max-width: 1120px;
  margin: 0 auto;
}

pre {
  overflow-x: auto;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: transparent;
  color: var(--ink);
}

.link-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  max-width: 1120px;
  margin: 0 auto;
}

.feature-link {
  display: grid;
  gap: 8px;
  min-height: 148px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  text-decoration: none;
}

.feature-link:hover {
  border-color: var(--teal);
}

.feature-link strong {
  font-size: 1.2rem;
  line-height: 1.18;
}

.feature-link span:last-child {
  color: var(--muted);
}

.method-stack {
  display: grid;
  gap: clamp(24px, 5vw, 52px);
  max-width: 920px;
  margin: 0 auto;
}

.method-stack article {
  display: grid;
  gap: 12px;
}

.method-stack h2,
.method-stack p {
  margin: 0;
}

.api-key-section {
  padding-top: clamp(12px, 3vw, 28px);
}

.api-key-layout {
  display: grid;
  grid-template-columns: minmax(320px, 0.9fr) minmax(0, 1fr);
  gap: clamp(24px, 5vw, 56px);
  max-width: 1120px;
  margin: 0 auto;
}

.api-key-form {
  align-self: start;
}

.api-status {
  min-height: 48px;
  padding: 12px;
  border: 1px solid rgba(13, 118, 111, 0.24);
  border-radius: 8px;
  background: #eef8f5;
  color: var(--teal-deep);
  font-weight: 700;
}

.api-status[data-state="error"] {
  border-color: rgba(168, 71, 50, 0.34);
  background: #fff2ef;
  color: var(--red);
}

.api-status[data-state="pending"] {
  background: #f7fbf9;
}

.api-dev-key {
  display: block;
  overflow-x: auto;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  color: var(--ink);
}

.api-info {
  display: grid;
  gap: 12px;
  align-content: start;
}

.api-info h2,
.api-info p {
  margin: 0;
}

.registry-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.registry-grid span {
  display: grid;
  gap: 4px;
  min-height: 72px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.registry-grid code {
  color: var(--teal-deep);
  font-size: 0.9rem;
  font-weight: 850;
}

.registry-grid small {
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.3;
}

.section-heading {
  max-width: 760px;
  margin: 0 auto 22px;
  text-align: center;
}

.examples-section {
  padding-top: clamp(40px, 7vw, 76px);
  border-block: 1px solid rgba(23, 32, 29, 0.08);
  background: var(--band);
}

.example-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  max-width: 1120px;
  margin: 0 auto;
}

.example-grid button {
  min-height: 58px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  text-align: left;
}

.paper-strip {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  border-top: 1px solid rgba(23, 32, 29, 0.08);
}

.paper-strip > div {
  max-width: 780px;
}

.primary-link {
  background: var(--teal-deep);
  color: #fff;
  white-space: nowrap;
}

@media (max-width: 980px) {
  .hero,
  .content-grid,
  .api-key-layout {
    grid-template-columns: 1fr;
  }

  .intro {
    position: static;
  }

  .conversion-grid,
  .example-grid,
  .link-grid,
  .registry-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .site-header,
  .paper-strip {
    align-items: flex-start;
    flex-direction: column;
  }

  nav {
    justify-content: flex-start;
  }

  form,
  #calculator-form,
  .input-section,
  .field-row,
  .calculator-result,
  .compare-answers,
  .advanced-options,
  .results,
  .conversion-grid,
  .example-grid,
  .link-grid,
  .registry-grid,
  .compare-row,
  .bar-row {
    grid-template-columns: 1fr;
  }

  .compare-head {
    align-items: flex-start;
    flex-direction: column;
  }

  .compare-head p {
    text-align: left;
  }

  .bar-value {
    text-align: left;
  }

  .field-row:nth-child(odd) {
    border-right: 0;
  }

  .input-pair {
    grid-template-columns: 1fr;
  }
}