:root {
  --surface: #ffffff;
  --panel: #f7f7f8;
  --ink: #111111;
  --muted: #5f6065;
  --line: #d8d8dc;
  --accent: #002fa7;
  --font: "Helvetica Neue", Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--surface);
  font-family: var(--font);
  line-height: 1.45;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

button,
input,
select {
  font: inherit;
}

.skip-link {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 100;
  padding: 12px 16px;
  color: var(--surface);
  background: var(--accent);
  transform: translateY(-110%);
}

.skip-link:focus {
  transform: translateY(0);
}

.tool-header,
footer {
  display: grid;
  grid-template-columns: minmax(180px, 1fr) minmax(0, 3fr);
  min-height: 72px;
  border-bottom: 1px solid var(--ink);
}

.tool-brand,
.tool-header nav,
footer > * {
  display: flex;
  align-items: center;
  min-height: 72px;
  padding: 16px 24px;
}

.tool-brand {
  border-right: 1px solid var(--ink);
  color: var(--ink);
  font-size: 1.1rem;
  font-weight: 700;
  text-decoration: none;
}

.tool-header nav {
  justify-content: flex-end;
  gap: 30px;
}

.tool-header nav a,
footer a {
  color: var(--ink);
  font-size: 0.92rem;
}

.tool-header .header-cta {
  min-width: 116px;
  padding: 11px 16px;
  color: var(--surface);
  background: var(--accent);
  text-align: center;
  text-decoration: none;
}

main {
  border-bottom: 1px solid var(--ink);
}

.tool-intro,
.calculator-grid,
.method-grid,
.source-grid,
.faq,
.next-grid {
  width: min(1440px, 100%);
  margin-inline: auto;
}

.tool-intro {
  display: grid;
  grid-template-columns: 1fr 3fr;
  min-height: 510px;
  border-bottom: 1px solid var(--ink);
}

.folio {
  margin: 0;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.tool-intro .folio {
  padding: 36px 24px;
  border-right: 1px solid var(--ink);
}

.tool-intro h1 {
  align-self: end;
  grid-column: 2;
  margin: 0;
  padding: 42px 40px 20px;
  font-size: clamp(4.2rem, 10vw, 9.5rem);
  font-weight: 700;
  letter-spacing: -0.07em;
  line-height: 0.82;
}

.tool-deck {
  grid-column: 2;
  max-width: 760px;
  margin: 0;
  padding: 20px 40px 42px;
  color: var(--muted);
  font-size: clamp(1.05rem, 2vw, 1.35rem);
}

.calculator-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  border-bottom: 1px solid var(--ink);
}

.calculator-form,
.calculator-result {
  min-width: 0;
  padding: 40px;
}

.calculator-form {
  border-right: 1px solid var(--ink);
}

.form-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 34px;
}

h2,
h3,
.result-empty h2 {
  margin: 0;
  font-weight: 700;
  letter-spacing: -0.045em;
}

h2 {
  font-size: clamp(2rem, 4vw, 3.7rem);
  line-height: 0.95;
}

h3 {
  font-size: 1.15rem;
}

.unit-field {
  display: flex;
  align-items: center;
  gap: 10px;
}

label > span,
.unit-field > span,
legend {
  display: block;
  margin-bottom: 7px;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

label > span b {
  color: var(--muted);
  font-weight: 500;
  text-transform: none;
}

input[type="number"],
select {
  width: 100%;
  min-height: 50px;
  padding: 11px 12px;
  border: 1px solid var(--ink);
  border-radius: 0;
  color: var(--ink);
  background: var(--surface);
}

input:focus,
select:focus,
button:focus-visible,
a:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
}

input[aria-invalid="true"] {
  border-color: var(--accent);
}

fieldset {
  margin: 0 0 28px;
  padding: 0;
  border: 0;
}

.field-note {
  max-width: 64ch;
  margin: 0 0 14px;
  color: var(--muted);
  font-size: 0.9rem;
}

.choice-row {
  display: flex;
  flex-wrap: wrap;
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
}

.choice-row label {
  display: flex;
  flex: 1 1 190px;
  align-items: center;
  gap: 10px;
  min-height: 50px;
  padding: 10px 12px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  cursor: pointer;
}

.choice-row input {
  width: 18px;
  height: 18px;
  margin: 0;
  accent-color: var(--accent);
}

.field-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  margin-bottom: 28px;
}

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

.form-message {
  min-height: 24px;
  margin: 6px 0 12px;
  color: var(--muted);
  font-size: 0.9rem;
}

.calculate-button,
.result-cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 54px;
  padding: 14px 20px;
  border: 1px solid var(--accent);
  border-radius: 0;
  color: var(--surface);
  background: var(--accent);
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
}

.calculate-button:hover,
.result-cta:hover,
.header-cta:hover {
  color: var(--accent);
  background: var(--surface);
}

.calculator-result {
  display: flex;
  min-height: 760px;
  background: var(--panel);
}

.result-empty,
.result-output {
  width: 100%;
}

.result-empty {
  align-self: center;
}

.result-empty h2 {
  max-width: 9ch;
  margin: 28px 0 18px;
  font-size: clamp(3rem, 6vw, 6rem);
  line-height: 0.9;
}

.result-empty > p:last-child {
  max-width: 42ch;
  color: var(--muted);
}

.result-index {
  margin: 0;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.target-number {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 24px 0 14px;
  border-bottom: 1px solid var(--ink);
  color: var(--accent);
}

.target-number strong {
  font-size: clamp(5rem, 12vw, 10rem);
  font-weight: 700;
  letter-spacing: -0.08em;
  line-height: 0.8;
  font-variant-numeric: tabular-nums;
}

.target-number span {
  font-size: 1rem;
  font-weight: 700;
}

.target-context,
.result-note {
  margin: 16px 0 28px;
  color: var(--muted);
}

.energy-grid,
.macro-grid {
  display: grid;
  margin: 0;
  border-top: 1px solid var(--ink);
  border-left: 1px solid var(--ink);
}

.energy-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-bottom: 34px;
}

.macro-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 14px 0 0;
}

.energy-grid div,
.macro-grid div {
  padding: 16px;
  border-right: 1px solid var(--ink);
  border-bottom: 1px solid var(--ink);
}

dt {
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

dd {
  margin: 8px 0 0;
  font-size: clamp(1.25rem, 3vw, 2rem);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.method-grid,
.source-grid,
.next-grid {
  display: grid;
  grid-template-columns: 1fr 3fr;
  border-bottom: 1px solid var(--ink);
}

.method-grid > div,
.source-grid > div,
.next-grid > div {
  padding: 48px 24px;
}

.method-grid > div:first-child,
.source-grid > div:first-child,
.next-grid > div:first-child {
  border-right: 1px solid var(--ink);
}

.method-grid h2,
.source-grid h2,
.next-grid h2 {
  margin-top: 28px;
}

.method-grid ol {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 0;
  padding: 0;
  list-style: none;
}

.method-grid li {
  padding: 48px 24px;
  border-right: 1px solid var(--line);
}

.method-grid li:last-child {
  border-right: 0;
}

.method-grid strong {
  display: block;
  margin-bottom: 14px;
  color: var(--accent);
}

.source-grid > div:last-child,
.next-grid > div:last-child {
  max-width: 860px;
}

.source-grid p,
.next-grid p {
  margin: 0 0 18px;
  font-size: 1.05rem;
}

.faq {
  padding: 48px 24px 72px;
  border-bottom: 1px solid var(--ink);
}

.faq h2 {
  margin: 24px 0 36px;
}

details {
  border-top: 1px solid var(--ink);
}

details:last-child {
  border-bottom: 1px solid var(--ink);
}

summary {
  min-height: 58px;
  padding: 18px 0;
  color: var(--ink);
  font-weight: 700;
  cursor: pointer;
}

details p {
  max-width: 760px;
  margin: 0 0 24px;
  color: var(--muted);
}

.next-links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px 26px;
  margin-top: 28px;
}

.next-links a:first-child {
  display: inline-flex;
  align-items: center;
  min-height: 50px;
  padding: 12px 18px;
  color: var(--surface);
  background: var(--accent);
  font-weight: 700;
  text-decoration: none;
}

footer {
  grid-template-columns: 1fr 2fr 1fr;
  border-bottom: 0;
}

footer > * {
  border-right: 1px solid var(--ink);
}

footer > *:last-child {
  border-right: 0;
}

footer span {
  color: var(--muted);
}

footer nav {
  justify-content: flex-end;
  gap: 18px;
}

[hidden] {
  display: none !important;
}

@media (max-width: 900px) {
  .tool-header,
  .tool-intro,
  .calculator-grid,
  .method-grid,
  .source-grid,
  .next-grid,
  footer {
    grid-template-columns: 1fr;
  }

  .tool-brand,
  .tool-intro .folio,
  .calculator-form,
  .method-grid > div:first-child,
  .source-grid > div:first-child,
  .next-grid > div:first-child,
  footer > * {
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }

  .tool-header nav {
    justify-content: flex-start;
    overflow-x: auto;
  }

  .tool-intro {
    min-height: 420px;
  }

  .tool-intro h1,
  .tool-deck {
    grid-column: 1;
  }

  .tool-intro h1 {
    padding-top: 72px;
  }

  .calculator-result {
    min-height: 620px;
  }

  .method-grid ol {
    grid-template-columns: 1fr;
  }

  .method-grid li {
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }
}

@media (max-width: 620px) {
  .tool-header nav a:not(.header-cta) {
    display: none;
  }

  .tool-intro h1,
  .tool-deck,
  .calculator-form,
  .calculator-result,
  .method-grid > div,
  .source-grid > div,
  .next-grid > div,
  .faq {
    padding-left: 20px;
    padding-right: 20px;
  }

  .tool-intro h1 {
    font-size: clamp(3.5rem, 18vw, 5.5rem);
  }

  .form-heading {
    align-items: flex-start;
    flex-direction: column;
  }

  .field-grid,
  .field-grid.three,
  .energy-grid,
  .macro-grid {
    grid-template-columns: 1fr;
  }

  .calculator-result {
    min-height: 540px;
  }

  .target-number strong {
    font-size: clamp(4.5rem, 24vw, 7.5rem);
  }

  footer nav {
    justify-content: flex-start;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}