/* ============================================================
   Ledger — mortgage calculator
   Dark, high-end aesthetic: near-black walls, electric blue
   reserved strictly for CTAs / active nav / hover / focus,
   crisp white for headings and body text.
   Type: Fraunces (headline), IBM Plex Sans (body/UI),
         IBM Plex Mono (all numeric data)
   ============================================================ */

:root {
  --wall: #0A0A0C;
  --wall-raised: #131316;
  --wall-panel: #17181C;
  --white: #F6F7F9;
  --white-soft: #A6A9B2;
  --white-faint: #6B6E77;
  --electric: #3B7DFF;
  --electric-dim: #2A5BC4;
  --line: #232429;
  --line-strong: #303138;

  --font-head: "Fraunces", Georgia, serif;
  --font-body: "IBM Plex Sans", -apple-system, sans-serif;
  --font-mono: "IBM Plex Mono", "SFMono-Regular", Menlo, monospace;

  --radius: 3px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

body {
  margin: 0;
  background: var(--wall);
  color: var(--white);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--white); text-decoration-thickness: 1px; }
a:hover { color: var(--electric); }

:focus-visible {
  outline: 2px solid var(--electric);
  outline-offset: 2px;
}

/* ---------- masthead ---------- */

.masthead {
  border-bottom: 1px solid var(--line);
  background: var(--wall-raised);
}

.masthead__inner {
  max-width: 880px;
  margin: 0 auto;
  padding: 22px 24px;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}

.masthead__mark {
  font-family: var(--font-head);
  font-size: 1.55rem;
  font-weight: 500;
  font-style: italic;
  font-optical-sizing: auto;
  color: var(--white);
  letter-spacing: 0.01em;
  text-decoration: none;
}

.masthead__mark:hover { color: var(--white); text-decoration: none; }

.masthead__nav { display: flex; gap: 28px; }

.masthead__nav a {
  font-size: 0.9rem;
  color: var(--white-soft);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.masthead__nav a:hover { color: var(--electric); border-bottom-color: var(--electric); }

/* ---------- ad slots ---------- */

.ad-slot {
  max-width: 880px;
  margin: 28px auto;
  padding: 0 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.ad-slot__label {
  font-size: 0.7rem;
  color: var(--white-faint);
  margin-bottom: 6px;
  font-family: var(--font-mono);
}

.ad-slot__placeholder {
  width: 100%;
  max-width: 728px;
  min-height: 90px;
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white-faint);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  background: var(--wall-raised);
}

.ad-slot--incontent .ad-slot__placeholder { max-width: 336px; min-height: 280px; }

/* ---------- hero ---------- */

.hero {
  max-width: 680px;
  margin: 0 auto;
  padding: 56px 24px 8px;
  text-align: left;
}

.hero__kicker {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--white-faint);
  margin: 0 0 14px;
}

.hero__lead {
  font-family: var(--font-body);
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--white);
  margin: 0 0 16px;
  max-width: 40ch;
}

.hero__title {
  font-family: var(--font-head);
  font-size: clamp(1.9rem, 4vw, 2.6rem);
  font-weight: 500;
  line-height: 1.2;
  margin: 0 0 16px;
  max-width: 18ch;
  color: var(--white);
}

.hero__sub {
  color: var(--white-soft);
  font-size: 1.05rem;
  max-width: 52ch;
  margin: 0;
}

/* ---------- calculator ---------- */

.calculator {
  max-width: 880px;
  margin: 40px auto 0;
  padding: 0 24px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.calculator__inputs {
  background: var(--wall-panel);
  padding: 32px;
  display: flex;
  flex-direction: column;
  gap: 22px;
  border-right: 1px solid var(--line);
}

.field label {
  display: block;
  font-size: 0.85rem;
  color: var(--white-soft);
  margin-bottom: 6px;
}

.field__control {
  display: flex;
  align-items: center;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--wall);
  padding: 8px 12px;
  transition: border-color 0.15s ease;
}

.field__control:focus-within {
  border-color: var(--electric);
}

.field__control input {
  border: none;
  background: transparent;
  font-family: var(--font-mono);
  font-size: 1.15rem;
  color: var(--white);
  width: 100%;
  padding: 0;
}

.field__control input:focus { outline: none; }

.field__prefix, .field__suffix {
  font-family: var(--font-mono);
  color: var(--white-faint);
  font-size: 1.05rem;
}

.field__prefix { margin-right: 4px; }
.field__suffix { margin-left: 4px; }

.field__range {
  width: 100%;
  margin-top: 10px;
  accent-color: var(--electric);
}

.calculator__result {
  background: var(--wall);
  color: var(--white);
  padding: 40px 32px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.result__label {
  font-size: 0.9rem;
  color: var(--white-soft);
  margin: 0 0 6px;
}

.result__figure {
  font-family: var(--font-mono);
  font-size: clamp(2.2rem, 5vw, 3rem);
  font-weight: 500;
  color: var(--white);
  margin: 0 0 28px;
  letter-spacing: -0.01em;
}

.result__breakdown {
  display: grid;
  gap: 14px;
  margin: 0;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.result__breakdown div {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}

.result__breakdown dt {
  color: var(--white-soft);
  font-size: 0.85rem;
}

.result__breakdown dd {
  font-family: var(--font-mono);
  margin: 0;
  color: var(--white);
  font-size: 1rem;
}

/* ---------- schedule / chart ---------- */

.schedule {
  max-width: 880px;
  margin: 56px auto 0;
  padding: 0 24px;
}

.schedule__title {
  font-family: var(--font-head);
  font-size: 1.5rem;
  font-weight: 500;
  margin: 0 0 6px;
  color: var(--white);
}

.schedule__sub {
  color: var(--white-soft);
  margin: 0 0 24px;
  max-width: 60ch;
}

.schedule__chart-wrap {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--wall-panel);
  padding: 16px;
}

.chart-frame {
  position: relative;
}

#balance-chart {
  width: 100%;
  height: auto;
  display: block;
  cursor: crosshair;
}

.chart-axis-label {
  font-family: var(--font-mono);
  font-size: 10px;
  fill: var(--white-faint);
}

.chart-hover-line {
  stroke: var(--electric);
  stroke-width: 1;
  opacity: 0;
  pointer-events: none;
}

.chart-hover-dot {
  fill: var(--electric);
  stroke: var(--wall-panel);
  stroke-width: 2;
  opacity: 0;
  pointer-events: none;
}

.chart-tooltip {
  position: absolute;
  top: 0;
  left: 0;
  transform: translate(-50%, -110%);
  background: var(--wall);
  border: 1px solid var(--electric);
  border-radius: var(--radius);
  padding: 8px 12px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--white);
  white-space: nowrap;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.1s ease;
  z-index: 5;
}

.chart-tooltip.is-visible { opacity: 1; }

.chart-tooltip__year {
  color: var(--white-soft);
  margin-bottom: 4px;
}

.chart-tooltip__row {
  display: flex;
  justify-content: space-between;
  gap: 16px;
}

.chart-tooltip__row + .chart-tooltip__row { margin-top: 2px; }

.schedule__legend {
  display: flex;
  gap: 24px;
  margin-top: 14px;
  font-size: 0.85rem;
  color: var(--white-soft);
}

.dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-right: 6px;
}

.dot--balance { background: var(--white); }
.dot--interest { background: var(--white-faint); }

/* ---------- guide ---------- */

.guide {
  max-width: 680px;
  margin: 64px auto 0;
  padding: 0 24px;
}

.guide h2 {
  font-family: var(--font-head);
  font-size: 1.4rem;
  font-weight: 500;
  margin: 0 0 16px;
  color: var(--white);
}

.guide h3 {
  font-family: var(--font-body);
  font-size: 1.05rem;
  font-weight: 600;
  margin: 32px 0 10px;
  color: var(--white);
}

.guide p {
  color: var(--white-soft);
  max-width: 62ch;
  margin: 0 0 4px;
}

/* ---------- FAQ ---------- */

.faq {
  max-width: 680px;
  margin: 56px auto 0;
  padding: 0 24px;
}

.faq h2 {
  font-family: var(--font-head);
  font-size: 1.4rem;
  font-weight: 500;
  margin: 0 0 20px;
  color: var(--white);
}

.faq__item {
  border-top: 1px solid var(--line);
  padding: 16px 0;
}

.faq__item:last-child {
  border-bottom: 1px solid var(--line);
}

.faq__item summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--white);
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.faq__item summary::-webkit-details-marker { display: none; }

.faq__item summary::after {
  content: "+";
  font-family: var(--font-mono);
  color: var(--white-faint);
  font-size: 1.2rem;
  margin-left: 16px;
  transition: transform 0.15s ease, color 0.15s ease;
}

.faq__item[open] summary::after {
  content: "−";
}

.faq__item summary:hover::after {
  color: var(--electric);
}

.faq__item p {
  color: var(--white-soft);
  margin: 12px 0 0;
  max-width: 62ch;
}

/* ---------- footer ---------- */

.site-footer {
  border-top: 1px solid var(--line);
  margin-top: 64px;
}

.site-footer__inner {
  max-width: 880px;
  margin: 0 auto;
  padding: 28px 24px 40px;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
  color: var(--white-faint);
}

.site-footer__inner p { margin: 0; max-width: 52ch; }
.site-footer__inner nav { display: flex; gap: 20px; }
.site-footer__inner nav a { color: var(--white-soft); }
.site-footer__inner nav a:hover { color: var(--electric); }

/* ---------- responsive ---------- */

@media (max-width: 720px) {
  .calculator {
    grid-template-columns: 1fr;
  }
  .calculator__inputs {
    border-right: none;
    border-bottom: 1px solid var(--line);
  }
  .masthead__nav { display: none; }
}

@media (max-width: 480px) {
  .hero { padding: 40px 16px 8px; }
  .calculator, .schedule, .guide, .ad-slot, .site-footer__inner { padding-left: 16px; padding-right: 16px; }
  .calculator__inputs, .calculator__result { padding: 24px 20px; }
  .schedule__chart-wrap { padding: 10px; }
}