:root {
  color-scheme: light dark;
  --color-bg: #f5f7f6;
  --color-surface: #ffffff;
  --color-surface-alt: #eef4f2;
  --color-border: rgba(15, 118, 85, 0.12);
  --color-text: #13211d;
  --color-muted: #536661;
  --color-muted-strong: #32423d;
  --color-primary: #0f7655;
  --color-primary-dark: #0a5e43;
  --color-primary-light: #1ea274;
  --gradient-primary: linear-gradient(135deg, #0f7655, #0a5e43 70%);
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --shadow-soft: 0 24px 48px -24px rgba(13, 74, 53, 0.45);
  --shadow-subtle: 0 1px 0 rgba(15, 118, 85, 0.08), 0 8px 16px -12px rgba(15, 118, 85, 0.35);
  --font-sans: 'Inter', 'Segoe UI', system-ui, -apple-system, BlinkMacSystemFont, 'Roboto', sans-serif;
  --transition-fast: 160ms ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0d1412;
    --color-surface: #17221f;
    --color-surface-alt: #0f1a17;
    --color-border: rgba(30, 162, 116, 0.25);
    --color-text: #f5faf8;
    --color-muted: #9cb8ae;
    --color-muted-strong: #d0ede2;
    --shadow-soft: 0 30px 60px -30px rgba(0, 0, 0, 0.7);
    --shadow-subtle: 0 1px 0 rgba(18, 28, 25, 0.9), 0 10px 20px -16px rgba(0, 0, 0, 0.65);
  }
}

* {
  box-sizing: border-box;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

img,
svg {
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
}

a:hover,
a:focus-visible {
  text-decoration: underline;
}

button {
  font: inherit;
  color: inherit;
  border: none;
  background: none;
  cursor: pointer;
}

button:disabled,
.is-disabled {
  cursor: not-allowed;
}

.skip-link {
  position: absolute;
  top: -40px;
  left: 16px;
  background: var(--color-primary);
  color: #fff;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  transition: top var(--transition-fast);
  z-index: 1000;
}

.skip-link:focus-visible {
  top: 16px;
}

.page-header {
  padding: 2.5rem clamp(1.25rem, 4vw, 3rem) 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.page-nav {
  margin-top: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  font-size: 0.95rem;
}

.page-nav a {
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
  border: 1px solid transparent;
  transition: border var(--transition-fast), background var(--transition-fast);
}

.page-nav a:hover,
.page-nav a:focus-visible {
  border-color: rgba(15, 118, 85, 0.35);
  background: rgba(15, 118, 85, 0.12);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.5rem;
  font-weight: 600;
}

.brand__mark {
  width: 44px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 14px;
  background: var(--gradient-primary);
  color: #fff;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.tagline {
  margin: 0;
  max-width: 42ch;
  color: var(--color-muted);
}

.layout {
  display: grid;
  grid-template-columns: minmax(0, 3fr) minmax(260px, 1fr);
  gap: clamp(1.5rem, 4vw, 2.5rem);
  padding: 0 clamp(1.25rem, 5vw, 3rem) clamp(3rem, 5vw, 4rem);
  align-items: start;
}

.layout__primary {
  display: flex;
  flex-direction: column;
  gap: clamp(1.5rem, 4vw, 2.5rem);
}

.layout__aside {
  position: relative;
}

.sidebar {
  position: sticky;
  top: clamp(1.5rem, 5vw, 3rem);
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: 1.5rem 1.25rem;
  box-shadow: var(--shadow-subtle);
  border: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.sidebar__nav {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.sidebar__link {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 0.85rem;
  border-radius: var(--radius-md);
  background: transparent;
  border: 1px solid transparent;
  color: var(--color-muted);
  transition: background var(--transition-fast), border var(--transition-fast), color var(--transition-fast);
}

.sidebar__link:focus-visible {
  outline: 3px solid rgba(30, 162, 116, 0.45);
  outline-offset: 2px;
}

.sidebar__link.is-active {
  background: var(--gradient-primary);
  color: #fff;
  border-color: rgba(255, 255, 255, 0.14);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.1);
}

.sidebar__link.is-disabled {
  opacity: 0.55;
  border: 1px dashed rgba(15, 118, 85, 0.25);
}

.sidebar__icon {
  width: 22px;
  height: 22px;
  flex-shrink: 0;
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  filter: brightness(0.82);
}

.sidebar__link.is-active .sidebar__icon {
  filter: brightness(1.12);
}

.sidebar__icon--length { background-image: url('./assets/length.svg'); }
.sidebar__icon--time { background-image: url('./assets/time.svg'); }
.sidebar__icon--area { background-image: url('./assets/area.svg'); }
.sidebar__icon--volume { background-image: url('./assets/volume.svg'); }
.sidebar__icon--number { background-image: url('./assets/number.svg'); }
.sidebar__icon--cost { background-image: url('./assets/cost.svg'); }
.sidebar__icon--power { background-image: url('./assets/power.svg'); }
.sidebar__icon--pressure { background-image: url('./assets/pressure.svg'); }
.sidebar__icon--more { background-image: url('./assets/more.svg'); }

.converter-card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: clamp(1.5rem, 4vw, 2.5rem);
  box-shadow: var(--shadow-soft);
  border: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.converter-card__header h1 {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  margin: 0;
}

.converter-card__sub {
  margin: 0.35rem 0 0;
  color: var(--color-muted);
}

.converter-card__author {
  margin: 0.25rem 0 0;
  font-size: 0.95rem;
  color: var(--color-muted);
}

.converter-card__author a {
  color: var(--color-primary);
  text-decoration: none;
}

.converter-card__author a:hover,
.converter-card__author a:focus-visible {
  text-decoration: underline;
}

.converter {
  display: flex;
  flex-direction: column;
  gap: clamp(1rem, 3vw, 1.5rem);
}

.converter__inputs {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  gap: clamp(1rem, 3vw, 1.5rem);
  align-items: end;
}

.converter__column {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.field-label {
  font-weight: 600;
  color: var(--color-muted-strong);
}

.input-stack {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.value-input {
  width: 100%;
  padding: 0.95rem 1.05rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: var(--color-surface-alt);
  font-size: 1.1rem;
  transition: border var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
}

.value-input:focus-visible {
  border-color: var(--color-primary-light);
  box-shadow: 0 0 0 3px rgba(30, 162, 116, 0.25);
  outline: none;
}

.value-input.is-invalid {
  border-color: #d64545;
  box-shadow: 0 0 0 2px rgba(214, 69, 69, 0.25);
}

.converter__swap {
  display: flex;
  align-items: center;
  justify-content: center;
}

.swap-button {
  width: clamp(52px, 4vw, 60px);
  height: clamp(52px, 4vw, 60px);
  border-radius: 50%;
  background: var(--gradient-primary);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-subtle);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.swap-button:focus-visible {
  outline: 3px solid rgba(30, 162, 116, 0.35);
  outline-offset: 3px;
}

.swap-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 20px 36px -24px rgba(10, 94, 67, 0.8);
}

.swap-button__icon {
  width: 26px;
  height: 26px;
  background: url('./assets/swap.svg') center / contain no-repeat;
}

.unit-select {
  position: relative;
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.25rem 0.35rem 0.25rem 0.25rem;
}

.unit-select.is-open {
  border-color: var(--color-primary-light);
  box-shadow: 0 0 0 3px rgba(30, 162, 116, 0.22);
}

.unit-select__toggle {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex: 1;
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.65rem;
  background: transparent;
}

.unit-select__toggle:focus-visible {
  outline: 2px solid rgba(30, 162, 116, 0.55);
  outline-offset: 2px;
}

.unit-select__primary {
  font-weight: 600;
}

.unit-select__symbol {
  color: var(--color-muted);
  font-size: 0.95rem;
}

.unit-select__chevron {
  width: 16px;
  height: 16px;
  background: url('./assets/chevron.svg') center / contain no-repeat;
  opacity: 0.65;
}

.unit-info {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: rgba(15, 118, 85, 0.12);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background var(--transition-fast);
}

.unit-info:focus-visible {
  outline: 2px solid rgba(30, 162, 116, 0.45);
  outline-offset: 2px;
}

.unit-info:hover {
  background: rgba(15, 118, 85, 0.2);
}

.unit-info__icon {
  width: 18px;
  height: 18px;
  background: url('./assets/info.svg') center / contain no-repeat;
}

.unit-info__bubble {
  position: absolute;
  inset-inline-end: 0;
  top: calc(100% + 0.4rem);
  min-width: min(320px, 92vw);
  padding: 0.85rem;
  background: var(--color-surface);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-subtle);
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  z-index: 20;
}

.unit-info__bubble strong {
  font-weight: 600;
}

.unit-info__bubble[hidden] {
  display: none;
}

.unit-select__panel {
  position: absolute;
  left: -1px;
  right: -1px;
  top: calc(100% + 0.4rem);
  z-index: 25;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-soft);
  padding: 0.75rem 0;
}

.unit-select__panel[hidden] {
  display: none;
}

.unit-select__search {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.55rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
  margin-bottom: 0.75rem;
  width: 100%;
}

.unit-select__icon {
  width: 18px;
  height: 18px;
  background: url('./assets/search.svg') center / contain no-repeat;
  opacity: 0.7;
}

.unit-select__search-input {
  border: none;
  background: transparent;
  outline: none;
  flex: 1;
  font-size: 0.95rem;
  min-width: 0;
}

.unit-select__options {
  max-height: min(320px, 60vh);
  overflow-y: auto;
  position: relative;
  padding: 0 0.75rem 0.25rem;
}

.unit-select__list {
  position: relative;
  display: grid;
  align-items: start;
}

.unit-select__option {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  grid-template-rows: auto auto;
  gap: 0.2rem 0.5rem;
  padding: 0.65rem 0.75rem;
  border-radius: var(--radius-md);
  cursor: pointer;
}

.unit-select__option-name {
  font-weight: 600;
}

.unit-select__option-symbol {
  justify-self: end;
  color: var(--color-muted);
  font-size: 0.95rem;
}

.unit-select__option-category {
  grid-column: 1 / -1;
  font-size: 0.8rem;
  color: var(--color-muted);
}

.unit-select__option:hover,
.unit-select__option.is-active {
  background: rgba(15, 118, 85, 0.1);
}

.unit-select__option.is-selected {
  box-shadow: inset 0 0 0 2px rgba(15, 118, 85, 0.35);
}

.unit-select__empty {
  padding: 0.75rem;
  text-align: center;
  color: var(--color-muted);
}

.converter__secondary {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
  justify-content: space-between;
}

.precision-controls {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  border: none;
  padding: 0;
  margin: 0;
}

.precision-controls legend {
  font-weight: 600;
  margin-right: 0.5rem;
}

.precision-option {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.65rem;
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
  border: 1px solid transparent;
  transition: border var(--transition-fast), background var(--transition-fast);
}

.precision-option:has(input:checked) {
  border-color: var(--color-primary-light);
  background: rgba(15, 118, 85, 0.13);
}

.precision-option input {
  accent-color: var(--color-primary);
}

.precision-select {
  margin-right: -0.25rem;
  font-size: 0.95rem;
  color: var(--color-muted);
}

#fixed-decimals {
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-border);
  padding: 0.45rem 0.6rem;
  background: var(--color-surface-alt);
  font-size: 0.95rem;
  transition: border var(--transition-fast), box-shadow var(--transition-fast);
}

#fixed-decimals:disabled {
  opacity: 0.5;
}

#fixed-decimals:focus-visible {
  border-color: var(--color-primary-light);
  box-shadow: 0 0 0 3px rgba(30, 162, 116, 0.25);
  outline: none;
}

.copy-controls {
  display: inline-flex;
  gap: 0.75rem;
}

.copy-button {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
  border: 1px solid transparent;
  transition: border var(--transition-fast), background var(--transition-fast);
}

.copy-button:hover {
  border-color: rgba(15, 118, 85, 0.4);
}

.copy-button:focus-visible {
  outline: 2px solid rgba(30, 162, 116, 0.55);
  outline-offset: 2px;
}

.copy-button__icon {
  width: 18px;
  height: 18px;
  background: url('./assets/copy.svg') center / contain no-repeat;
}

.popular {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: clamp(1.25rem, 4vw, 1.75rem);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-subtle);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.how-it-works,
.feature-grid,
.precision-details,
.services,
.faq {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: clamp(1.25rem, 4vw, 1.75rem);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-subtle);
  display: grid;
  gap: 0.85rem;
}

.how-it-works ul,
.services ul {
  margin: 0;
  padding-left: 1.1rem;
  display: grid;
  gap: 0.45rem;
  color: var(--color-muted);
}

.feature-grid__items {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

.feature-grid__items article {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  background: var(--color-surface-alt);
}

.precision-details dl {
  margin: 0;
  display: grid;
  gap: 0.5rem;
}

.precision-details dt {
  font-weight: 600;
  color: var(--color-muted-strong);
}

.precision-details dd {
  margin: 0;
  color: var(--color-muted);
}

.faq details {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 0.75rem 1rem;
  background: var(--color-surface-alt);
}

.faq details + details {
  margin-top: 0.5rem;
}

.faq summary {
  font-weight: 600;
  cursor: pointer;
}

.faq p {
  margin: 0.45rem 0 0;
  color: var(--color-muted);
}

.section-heading h2 {
  margin: 0;
}

.section-heading p {
  margin: 0.35rem 0 0;
  color: var(--color-muted);
}

.chips {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 0.65rem;
}

.chip {
  border-radius: 999px;
  padding: 0.45rem 1rem;
  background: rgba(15, 118, 85, 0.12);
  border: 1px solid transparent;
  font-weight: 600;
  transition: background var(--transition-fast), transform var(--transition-fast);
}

.chip:hover {
  background: rgba(15, 118, 85, 0.18);
  transform: translateY(-1px);
}

.chip:focus-visible {
  outline: 2px solid rgba(30, 162, 116, 0.5);
  outline-offset: 2px;
}

.references {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: clamp(1.25rem, 4vw, 1.75rem);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-subtle);
}

.references h2 {
  margin: 0;
}

.references ul {
  margin: 0.75rem 0 0;
  padding-left: 1.1rem;
  color: var(--color-muted);
  display: grid;
  gap: 0.5rem;
}

.site-footer {
  margin-top: clamp(2.5rem, 6vw, 3.5rem);
  padding: 1.5rem clamp(1.25rem, 5vw, 3rem) 2rem;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
}

.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
  justify-content: space-between;
  max-width: 1100px;
  margin: 0 auto;
  color: var(--color-muted);
}

.site-footer__note a,
.site-footer__links a {
  color: var(--color-primary);
  text-decoration: none;
}

.site-footer__links {
  display: inline-flex;
  gap: 1rem;
}

.site-footer__links a:hover,
.site-footer__links a:focus-visible,
.site-footer__note a:hover,
.site-footer__note a:focus-visible {
  text-decoration: underline;
}

@media (max-width: 600px) {
  .site-footer__inner {
    flex-direction: column;
    align-items: flex-start;
  }
}

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

.live-region {
  position: absolute;
  width: 1px;
  height: 1px;
  clip: rect(0, 0, 0, 0);
  overflow: hidden;
}

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

  .layout__aside {
    order: -1;
  }

  .sidebar {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 0.75rem;
    position: static;
  }

  .sidebar__nav {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 0.5rem;
  }

  .sidebar__link {
    flex: 1 1 42%;
  }
}

@media (max-width: 720px) {
  .page-nav {
    gap: 0.5rem;
  }

  .converter__inputs {
    grid-template-columns: 1fr;
  }

  .converter__swap {
    order: -1;
    justify-content: flex-start;
  }

  .swap-button {
    width: 52px;
    height: 52px;
  }

  .converter__secondary {
    flex-direction: column;
    align-items: stretch;
  }

  .copy-controls {
    width: 100%;
    justify-content: space-between;
  }

  .copy-button {
    flex: 1 1 auto;
    justify-content: center;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}