:root {
  color-scheme: dark;
  --bg: #07111f;
  --bg-soft: #0b1728;
  --panel: rgba(15, 29, 48, 0.9);
  --panel-strong: #102039;
  --panel-border: rgba(158, 184, 221, 0.16);
  --text: #f3f7ff;
  --muted: #9fb0c9;
  --muted-strong: #c4d1e4;
  --accent: #67e8c7;
  --accent-strong: #29cfa7;
  --accent-soft: rgba(103, 232, 199, 0.12);
  --blue: #74a8ff;
  --danger: #ff9d9d;
  --shadow: 0 24px 70px rgba(0, 0, 0, 0.3);
  --radius-lg: 24px;
  --radius-md: 16px;
  --radius-sm: 12px;
  --content-width: 1180px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  background: var(--bg);
}

body {
  min-width: 320px;
  margin: 0;
  color: var(--text);
  background:
    radial-gradient(circle at 15% -15%, rgba(73, 129, 209, 0.22), transparent 35rem),
    radial-gradient(circle at 95% 10%, rgba(30, 194, 154, 0.14), transparent 30rem),
    var(--bg);
  line-height: 1.6;
}

button,
input,
select {
  font: inherit;
}

button,
select {
  cursor: pointer;
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
summary:focus-visible {
  outline: 3px solid rgba(103, 232, 199, 0.42);
  outline-offset: 3px;
}

.skip-link {
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 100;
  padding: 10px 14px;
  color: #031710;
  background: var(--accent);
  border-radius: 10px;
  transform: translateY(-150%);
}

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

.site-header {
  border-bottom: 1px solid rgba(255, 255, 255, 0.07);
  background: rgba(7, 17, 31, 0.78);
  backdrop-filter: blur(16px);
}

.header-inner {
  width: min(calc(100% - 32px), var(--content-width));
  min-height: 72px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.brand,
.github-button {
  color: var(--text);
  text-decoration: none;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  font-size: 1rem;
  font-weight: 750;
  letter-spacing: -0.02em;
}

.github-button {
  min-height: 42px;
  padding: 0 15px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.04);
  font-size: 0.9rem;
  font-weight: 700;
  transition: border-color 160ms ease, background 160ms ease, transform 160ms ease;
}

.github-button:hover {
  border-color: rgba(103, 232, 199, 0.5);
  background: var(--accent-soft);
  transform: translateY(-1px);
}

main {
  overflow: hidden;
}

.hero,
.content-section {
  width: min(calc(100% - 32px), var(--content-width));
  margin: 0 auto;
}

.hero {
  padding: 68px 0 58px;
}

.hero-heading {
  max-width: 800px;
  margin-bottom: 34px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 900px;
  margin-bottom: 16px;
  font-size: clamp(2.15rem, 5.1vw, 4.5rem);
  line-height: 1.03;
  letter-spacing: -0.055em;
}

.hero-heading > p:last-child {
  max-width: 720px;
  margin-bottom: 0;
  color: var(--muted-strong);
  font-size: clamp(1rem, 1.6vw, 1.18rem);
}

.panel {
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-lg);
  background: linear-gradient(145deg, rgba(17, 34, 58, 0.97), rgba(11, 23, 40, 0.94));
  box-shadow: var(--shadow);
}

.calculator-shell {
  display: grid;
  grid-template-columns: minmax(0, 0.92fr) minmax(0, 1.08fr);
  gap: 20px;
}

.input-panel,
.result-panel {
  padding: clamp(22px, 3vw, 34px);
}

.panel-heading,
.charts-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 25px;
}

.panel-heading > div,
.charts-heading > div:first-child {
  display: flex;
  align-items: center;
  gap: 11px;
}

.panel-heading h2,
.charts-heading h2 {
  margin: 0;
  font-size: 1.08rem;
  letter-spacing: -0.02em;
}

.step-label {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  color: var(--accent);
  border: 1px solid rgba(103, 232, 199, 0.25);
  border-radius: 10px;
  background: var(--accent-soft);
  font-size: 0.72rem;
  font-weight: 850;
}

.status-dot {
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 6px rgba(103, 232, 199, 0.09);
}

.result-state {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.mode-switch {
  margin: 0 0 24px;
  padding: 5px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  border: 1px solid var(--panel-border);
  border-radius: 13px;
  background: rgba(0, 0, 0, 0.17);
}

.mode-switch label {
  position: relative;
}

.mode-switch input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.mode-switch span {
  min-height: 42px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  border-radius: 9px;
  font-size: 0.88rem;
  font-weight: 750;
  transition: color 160ms ease, background 160ms ease;
}

.mode-switch input:checked + span {
  color: var(--text);
  background: rgba(255, 255, 255, 0.08);
  box-shadow: 0 5px 18px rgba(0, 0, 0, 0.18);
}

.field-group {
  margin-bottom: 23px;
}

.two-column-fields {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 13px;
}

.field > span:first-child {
  display: block;
  margin-bottom: 8px;
  color: var(--muted-strong);
  font-size: 0.82rem;
  font-weight: 700;
}

.field input,
.field select {
  width: 100%;
  min-height: 52px;
  color: var(--text);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  background: rgba(4, 13, 24, 0.55);
}

.field input {
  padding: 0 15px;
}

.field select {
  padding: 0 42px 0 15px;
}

.field input:hover,
.field select:hover {
  border-color: rgba(159, 176, 201, 0.4);
}

.field input:focus,
.field select:focus {
  border-color: var(--accent-strong);
  box-shadow: 0 0 0 3px rgba(103, 232, 199, 0.1);
  outline: none;
}

.compound-field {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(120px, 0.48fr);
  gap: 9px;
}

.route-distance {
  margin-top: 13px;
  padding: 12px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 15px;
  border: 1px solid rgba(103, 232, 199, 0.13);
  border-radius: 12px;
  background: rgba(103, 232, 199, 0.055);
}

.route-distance span,
.field-note {
  color: var(--muted);
  font-size: 0.78rem;
}

.route-distance strong {
  color: var(--accent);
  font-size: 0.88rem;
}

.field-note {
  margin: 8px 2px 0;
}

.preset-row {
  margin-top: 10px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.preset-button {
  min-width: 60px;
  min-height: 35px;
  padding: 0 11px;
  color: var(--muted);
  border: 1px solid var(--panel-border);
  border-radius: 9px;
  background: transparent;
  font-size: 0.78rem;
  font-weight: 750;
}

.preset-button:hover,
.preset-button.active {
  color: var(--accent);
  border-color: rgba(103, 232, 199, 0.32);
  background: var(--accent-soft);
}

.form-error {
  min-height: 24px;
  margin: -6px 0 8px;
  color: var(--danger);
  font-size: 0.82rem;
  font-weight: 650;
}

.primary-button,
.secondary-button {
  min-height: 50px;
  border-radius: 12px;
  font-weight: 800;
}

.primary-button {
  width: 100%;
  padding: 0 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  color: #041911;
  border: 0;
  background: var(--accent);
  box-shadow: 0 15px 35px rgba(41, 207, 167, 0.16);
  transition: background 160ms ease, transform 160ms ease;
}

.primary-button:hover {
  background: #83f2d6;
  transform: translateY(-1px);
}

.primary-result {
  padding: 4px 0 24px;
  border-bottom: 1px solid var(--panel-border);
}

.primary-result span,
.metric-card span {
  display: block;
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 750;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.primary-result strong {
  display: block;
  margin: 4px 0 2px;
  font-size: clamp(2rem, 4vw, 3.5rem);
  line-height: 1.08;
  letter-spacing: -0.055em;
}

.primary-result small,
.metric-card small {
  color: var(--muted);
  font-size: 0.79rem;
}

.result-grid {
  padding: 20px 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 11px;
}

.metric-card {
  min-height: 112px;
  padding: 16px;
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  background: rgba(5, 16, 29, 0.36);
}

.metric-card strong {
  display: block;
  margin: 8px 0 3px;
  font-size: 1.06rem;
  line-height: 1.25;
}

.model-summary {
  margin-bottom: 17px;
  padding: 13px 14px;
  display: grid;
  gap: 10px;
  color: var(--muted);
  border: 1px solid rgba(116, 168, 255, 0.16);
  border-radius: 13px;
  background: rgba(116, 168, 255, 0.055);
  font-size: 0.75rem;
}

.model-summary > div {
  display: flex;
  align-items: flex-start;
  gap: 10px;
}

.model-summary p {
  margin: 0;
}

.model-summary strong {
  color: var(--muted-strong);
}

.model-icon {
  color: var(--blue);
  font-size: 1.15rem;
}

.result-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.secondary-button {
  padding: 0 13px;
  color: var(--text);
  border: 1px solid var(--panel-border);
  background: rgba(255, 255, 255, 0.035);
  font-size: 0.82rem;
}

.secondary-button:hover {
  border-color: rgba(103, 232, 199, 0.37);
  background: var(--accent-soft);
}

.charts-panel {
  margin-top: 20px;
  padding: clamp(22px, 3vw, 32px);
}

.charts-heading {
  margin-bottom: 20px;
}

.chart-legend {
  display: flex;
  align-items: center;
  gap: 7px;
  color: var(--muted);
  font-size: 0.75rem;
}

.chart-legend span {
  width: 16px;
  border-top: 1px dashed var(--accent);
}

.charts-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.chart-card {
  margin: 0;
  padding: 17px;
  overflow: hidden;
  border: 1px solid var(--panel-border);
  border-radius: 15px;
  background: rgba(4, 13, 24, 0.35);
}

.chart-card figcaption {
  margin-bottom: 8px;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 15px;
}

.chart-card figcaption strong {
  font-size: 0.88rem;
}

.chart-card figcaption span {
  color: var(--muted);
  font-size: 0.7rem;
  text-align: right;
}

.chart {
  width: 100%;
  height: auto;
  display: block;
  overflow: visible;
}

.content-section {
  padding: 78px 0;
  border-top: 1px solid rgba(255, 255, 255, 0.07);
}

.content-heading {
  max-width: 730px;
  margin-bottom: 34px;
}

.content-heading h2 {
  margin-bottom: 14px;
  font-size: clamp(1.8rem, 3.5vw, 3rem);
  line-height: 1.1;
  letter-spacing: -0.045em;
}

.content-heading > p:last-child,
.process-grid p,
.use-case-grid p,
.formula-card p,
.faq-list p {
  color: var(--muted);
}

.process-grid,
.use-case-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.process-grid article,
.use-case-grid article,
.formula-card {
  padding: 24px;
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-md);
  background: rgba(15, 29, 48, 0.58);
}

.process-grid article > span {
  display: inline-flex;
  width: 31px;
  height: 31px;
  margin-bottom: 28px;
  align-items: center;
  justify-content: center;
  color: var(--accent);
  border: 1px solid rgba(103, 232, 199, 0.24);
  border-radius: 9px;
  background: var(--accent-soft);
  font-size: 0.78rem;
  font-weight: 850;
}

.process-grid h3,
.use-case-grid h3 {
  margin-bottom: 8px;
  font-size: 1.05rem;
}

.process-grid p,
.use-case-grid p {
  margin-bottom: 0;
  font-size: 0.9rem;
}

.split-content {
  display: grid;
  grid-template-columns: 0.82fr 1.18fr;
  align-items: start;
  gap: 50px;
}

.split-content .content-heading {
  margin-bottom: 0;
}

.formula-card {
  padding: clamp(24px, 4vw, 38px);
}

.formula {
  margin: 12px 0;
  padding: 14px 16px;
  color: var(--accent);
  border: 1px solid rgba(103, 232, 199, 0.14);
  border-radius: 11px;
  background: rgba(4, 13, 24, 0.44);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: clamp(0.8rem, 2vw, 1rem);
  overflow-x: auto;
}

.faq-list {
  display: grid;
  gap: 10px;
}

.faq-list details {
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  background: rgba(15, 29, 48, 0.55);
}

.faq-list summary {
  padding: 18px 20px;
  cursor: pointer;
  font-weight: 750;
}

.faq-list p {
  padding: 0 20px 18px;
  margin: 0;
  font-size: 0.9rem;
}

footer {
  width: min(calc(100% - 32px), var(--content-width));
  margin: 0 auto;
  padding: 30px 0 38px;
  color: var(--muted);
  border-top: 1px solid rgba(255, 255, 255, 0.07);
  font-size: 0.8rem;
  text-align: center;
}

[hidden] {
  display: none !important;
}

@media (max-width: 900px) {
  .calculator-shell,
  .charts-grid,
  .split-content {
    grid-template-columns: 1fr;
  }

  .split-content {
    gap: 24px;
  }

  .process-grid,
  .use-case-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 600px) {
  .header-inner,
  .hero,
  .content-section,
  footer {
    width: min(calc(100% - 22px), var(--content-width));
  }

  .site-header .brand span {
    display: none;
  }

  .github-button {
    min-height: 40px;
  }

  .hero {
    padding-top: 46px;
  }

  h1 {
    font-size: clamp(2.15rem, 12vw, 3.25rem);
  }

  .input-panel,
  .result-panel,
  .charts-panel {
    padding: 19px;
    border-radius: 19px;
  }

  .two-column-fields,
  .result-grid,
  .result-actions {
    grid-template-columns: 1fr;
  }

  .compound-field {
    grid-template-columns: minmax(0, 1fr) minmax(112px, 0.65fr);
  }

  .primary-result strong {
    font-size: 2.25rem;
  }

  .chart-card {
    padding: 12px;
  }

  .chart-card figcaption {
    display: block;
  }

  .chart-card figcaption span {
    display: block;
    margin-top: 3px;
    text-align: left;
  }

  .charts-heading {
    align-items: flex-start;
  }

  .chart-legend {
    display: none;
  }

  .content-section {
    padding: 58px 0;
  }
}

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