:root {
  /* Customization point: update brand colors here. */
  --color-primary: #0f766e;
  --color-primary-strong: #0b5f59;
  --color-accent: #2563eb;
  --color-bg: #f6f8fb;
  --color-surface: #ffffff;
  --color-surface-muted: #eef4f7;
  --color-text: #172033;
  --color-muted: #5f6b7a;
  --color-border: #d7e0e7;
  --color-ad: #e8eef5;
  --shadow-panel: 0 20px 45px rgba(23, 32, 51, 0.1);
  --radius: 8px;
  --max-width: 1160px;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --color-bg: #101820;
  --color-surface: #18232d;
  --color-surface-muted: #22313d;
  --color-text: #edf5f7;
  --color-muted: #a8b6bf;
  --color-border: #304452;
  --color-ad: #1d2b36;
  --shadow-panel: 0 20px 45px rgba(0, 0, 0, 0.25);
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

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

a {
  color: inherit;
}

button,
input,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 5;
  background: color-mix(in srgb, var(--color-surface) 92%, transparent);
  border-bottom: 1px solid var(--color-border);
  backdrop-filter: blur(12px);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width);
  min-height: 64px;
  margin: 0 auto;
  padding: 0 16px;
}

.brand,
.nav-link,
.site-footer a {
  text-decoration: none;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 750;
}

.nav-actions {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  display: inline-grid;
  width: 36px;
  height: 36px;
  place-items: center;
  border-radius: var(--radius);
  background: var(--color-primary);
  color: #fff;
  font-size: 0.82rem;
}

.theme-toggle,
.secondary-button,
.text-button,
.swap-button {
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
}

.theme-toggle {
  width: 42px;
  height: 42px;
  font-size: 1.2rem;
}

.hero {
  background:
    linear-gradient(135deg, rgba(15, 118, 110, 0.95), rgba(37, 99, 235, 0.82)),
    radial-gradient(circle at 80% 20%, rgba(255, 255, 255, 0.25), transparent 32%);
  color: #fff;
}

.hero-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 44px 16px 52px;
}

.eyebrow {
  margin: 0 0 8px;
  font-size: 0.82rem;
  font-weight: 750;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2 {
  margin: 0;
  line-height: 1.15;
}

h1 {
  max-width: 760px;
  font-size: clamp(2rem, 8vw, 4rem);
}

.hero p:last-child {
  max-width: 670px;
  margin: 16px 0 0;
  font-size: 1.05rem;
}

.layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
  max-width: var(--max-width);
  margin: 18px auto;
  padding: 0 16px;
}

.calculator-panel,
.history-panel,
.content-page {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-panel);
}

.calculator-panel {
  padding: 18px;
}

.section-heading {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 18px;
}

.section-heading p {
  margin: 6px 0 0;
  color: var(--color-muted);
}

.compact {
  align-items: center;
  margin-bottom: 10px;
}

.field,
.unit-box {
  display: grid;
  gap: 8px;
}

label {
  color: var(--color-muted);
  font-size: 0.92rem;
  font-weight: 700;
}

input,
select {
  width: 100%;
  min-height: 48px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
  padding: 0 12px;
}

input:focus,
select:focus,
button:focus-visible,
a:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--color-accent) 45%, transparent);
  outline-offset: 2px;
}

.conversion-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin-top: 16px;
}

.unit-box {
  padding: 14px;
  background: var(--color-surface-muted);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.swap-button {
  justify-self: center;
  width: 44px;
  height: 44px;
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
  font-size: 1.3rem;
}

.result-actions {
  display: grid;
  gap: 14px;
  margin-top: 18px;
  padding: 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
}

.result {
  min-width: 0;
  overflow-wrap: anywhere;
  font-size: 1.1rem;
  font-weight: 800;
}

.button-group {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.secondary-button,
.text-button {
  min-height: 42px;
  padding: 0 14px;
  font-weight: 700;
}

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

.secondary-button:hover,
.swap-button:hover {
  background: var(--color-primary-strong);
}

.text-button {
  background: transparent;
  color: var(--color-primary);
}

.status {
  min-height: 24px;
  margin: 10px 0 0;
  color: var(--color-muted);
}

.side-column {
  display: grid;
  gap: 18px;
}

.history-panel {
  padding: 16px;
}

.history-list {
  display: grid;
  gap: 8px;
  margin: 0;
  padding-left: 22px;
}

.history-list li {
  color: var(--color-muted);
  overflow-wrap: anywhere;
}

.ad-slot {
  display: grid;
  place-items: center;
  min-height: 92px;
  border: 1px dashed var(--color-border);
  border-radius: var(--radius);
  background: var(--color-ad);
  color: var(--color-muted);
  font-size: 0.85rem;
  text-transform: uppercase;
}

.ad-slot-wide {
  max-width: var(--max-width);
  margin: 18px auto;
  padding: 0 16px;
  background-clip: content-box;
}

.ad-slot-side {
  min-height: 260px;
}

.content-page {
  max-width: 820px;
  margin: 28px auto;
  padding: 24px 16px;
}

.content-page h1 {
  font-size: clamp(2rem, 7vw, 3rem);
}

.content-page h2 {
  margin-top: 28px;
  font-size: 1.35rem;
}

.content-page p {
  color: var(--color-muted);
}

.site-footer {
  display: grid;
  gap: 10px;
  max-width: var(--max-width);
  margin: 28px auto 0;
  padding: 24px 16px 36px;
  color: var(--color-muted);
}

.site-footer nav {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 24px;
  margin-bottom: 16px;
}

.footer-section h3 {
  margin: 0 0 10px;
  font-size: 0.95rem;
  font-weight: 750;
  color: var(--color-text);
}

.footer-list {
  display: grid;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.footer-list a {
  font-size: 0.9rem;
  text-decoration: underline;
  text-decoration-color: var(--color-primary);
}

.site-footer p {
  margin: 0;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* FAQ Section Styling */
.faq-section {
  max-width: var(--max-width);
  margin: 28px auto;
  padding: 24px 16px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-panel);
}

.faq-section h2 {
  margin-bottom: 20px;
  font-size: 1.75rem;
}

.faq-section h3 {
  margin: 18px 0 10px;
  font-size: 1.05rem;
  color: var(--color-text);
}

.faq-section p {
  margin: 0 0 16px;
  color: var(--color-muted);
  line-height: 1.6;
}

.faq-section a {
  color: var(--color-primary);
  text-decoration: underline;
}

.faq-section a:hover {
  color: var(--color-primary-strong);
}

.faq-section [itemscope] {
  margin-bottom: 24px;
}

.faq-section [itemscope]:last-child {
  margin-bottom: 0;
}

@media (min-width: 680px) {
  .calculator-panel {
    padding: 24px;
  }

  .conversion-grid {
    grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
    align-items: end;
  }

  .swap-button {
    align-self: center;
    margin-top: 28px;
  }

  .result-actions {
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
  }

  .faq-section {
    padding: 32px 28px;
  }

  .faq-section h2 {
    font-size: 2rem;
  }
}

@media (min-width: 1024px) {
  .layout {
    grid-template-columns: minmax(0, 1fr) 300px;
    align-items: start;
  }

  .hero-content {
    padding-top: 58px;
  }

  .site-footer nav {
    grid-template-columns: repeat(2, 1fr);
  }
}