:root {
  color-scheme: light;
  --app-surface: #fbfaf6;
  --app-panel: #fffefa;
  --app-ink: #222824;
  --app-muted: #687069;
  --app-line: #cfd3cc;
  --app-line-strong: #9fa79f;
  --app-accent: #245b49;
  --app-accent-soft: #e2ebe5;
  --app-danger: #9b2f2f;
  --app-danger-soft: #f8e9e7;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  max-width: 100%;
  overflow-x: hidden;
}

button,
input {
  font: inherit;
}

a {
  color: inherit;
}

:focus-visible {
  outline: 3px solid var(--app-accent);
  outline-offset: 3px;
}

.tool-shell,
.calculator-panel,
.visual-panel,
.input-row,
.result-grid,
.result-details,
.visual-metrics,
.formula-list,
.phase-list {
  min-width: 0;
}

.tool-shell {
  display: grid;
  grid-template-columns: minmax(0, .9fr) minmax(0, 1.1fr);
  border: 1px solid var(--app-line-strong);
  background: var(--app-surface);
}

.calculator-panel,
.visual-panel {
  min-width: 0;
  padding: 25px;
}

.calculator-panel {
  border-right: 1px solid var(--app-line);
}

.eyebrow,
.section-kicker {
  margin: 0 0 5px;
  color: var(--app-accent);
  font-size: .78rem;
  font-weight: 780;
  letter-spacing: .08em;
  text-transform: uppercase;
}

h2 {
  margin: 0;
  font-size: clamp(1.2rem, 2vw, 1.48rem);
  line-height: 1.4;
}

h3 {
  margin: 0;
  font-size: 1rem;
}

.values-fieldset {
  margin: 20px 0 0;
  padding: 0;
  border: 0;
}

.values-fieldset legend {
  margin-bottom: 10px;
  font-weight: 760;
}

.input-grid {
  display: grid;
  gap: 16px;
}

.input-row {
  display: grid;
  gap: 5px;
}

.input-row label {
  display: block;
  font-size: .86rem;
  font-weight: 760;
}

.input-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 50px;
  align-items: stretch;
  gap: 7px;
  min-width: 0;
}

.input-wrap input {
  width: 100%;
  min-width: 0;
  min-height: 45px;
  padding: 8px 10px;
  border: 1px solid var(--app-line-strong);
  border-radius: 0;
  color: var(--app-ink);
  background: #fff;
}

.input-wrap input:focus {
  border-color: var(--app-accent);
  outline: 3px solid var(--app-accent-soft);
  outline-offset: 0;
}

.input-wrap input[aria-invalid="true"] {
  border-color: var(--app-danger);
  background: #fff8f8;
}

.unit-mark {
  display: grid;
  place-items: center;
  min-width: 0;
  border: 1px solid var(--app-line-strong);
  background: var(--app-surface);
  color: var(--app-muted);
  font-size: .82rem;
  font-weight: 700;
}

.field-help,
.period-note {
  margin: 0;
  color: var(--app-muted);
  font-size: .75rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.period-note {
  margin-top: 13px;
  padding-left: 11px;
  border-left: 3px solid var(--app-line-strong);
}

.field-error {
  min-height: 1.3em;
  margin: 0;
  color: var(--app-danger);
  font-size: .8rem;
  line-height: 1.45;
  overflow-wrap: anywhere;
}

.form-error {
  margin: 15px 0 0;
  padding: 10px 12px;
  border-left: 4px solid var(--app-danger);
  background: var(--app-danger-soft);
  color: var(--app-danger);
  font-size: .84rem;
  font-weight: 700;
  overflow-wrap: anywhere;
}

.form-error[hidden],
.result-grid[hidden],
.result-details[hidden] {
  display: none;
}

.form-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 19px;
}

.button {
  min-height: 46px;
  padding: 9px 17px;
  border: 1px solid var(--app-accent);
  border-radius: 0;
  cursor: pointer;
  font-weight: 760;
}

.button-primary {
  color: #fff;
  background: var(--app-accent);
}

.button-primary:hover {
  background: #1d4d3e;
}

.button-secondary {
  color: var(--app-accent);
  background: transparent;
}

.button-secondary:hover {
  background: var(--app-accent-soft);
}

.result-box {
  margin-top: 20px;
  padding: 17px;
  border: 1px solid var(--app-line-strong);
  background: #fff;
}

.result-box[data-state="ready"] {
  border-color: var(--app-accent);
  background: var(--app-accent-soft);
}

.result-box[data-state="error"] {
  border-color: var(--app-danger);
  background: var(--app-danger-soft);
}

.result-label {
  margin: 0;
  color: var(--app-accent);
  font-size: .8rem;
  font-weight: 780;
}

.result-box[data-state="error"] .result-label {
  color: var(--app-danger);
}

.result-status {
  margin: 5px 0 0;
  color: var(--app-muted);
  font-size: .84rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin-top: 15px;
}

.result-card {
  display: grid;
  gap: 5px;
  min-width: 0;
  padding: 11px 10px;
  border: 1px solid rgba(36, 91, 73, .35);
  background: rgba(255, 255, 255, .72);
}

.result-card span {
  color: var(--app-muted);
  font-size: .73rem;
  font-weight: 760;
}

.result-card strong {
  color: var(--app-accent);
  font-size: clamp(1rem, 2.4vw, 1.34rem);
  line-height: 1.3;
  font-variant-numeric: tabular-nums;
  overflow-wrap: anywhere;
}

.result-details {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 16px 0 0;
  border-top: 1px solid rgba(36, 91, 73, .35);
  border-left: 1px solid rgba(36, 91, 73, .35);
}

.result-details div {
  min-width: 0;
  padding: 9px 10px;
  border-right: 1px solid rgba(36, 91, 73, .35);
  border-bottom: 1px solid rgba(36, 91, 73, .35);
}

.result-details .detail-wide {
  grid-column: 1 / -1;
}

.result-details dt {
  color: var(--app-muted);
  font-size: .74rem;
  font-weight: 760;
}

.result-details dd {
  margin: 3px 0 0;
  color: var(--app-ink);
  font-size: .8rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.visual-heading-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 14px;
}

.status-badge {
  flex: 0 0 auto;
  padding: 3px 8px;
  border: 1px solid var(--app-line-strong);
  background: var(--app-surface);
  color: var(--app-muted);
  font-size: .75rem;
  font-weight: 760;
  white-space: nowrap;
}

.status-badge[data-state="ready"] {
  border-color: var(--app-accent);
  background: var(--app-accent-soft);
  color: var(--app-accent);
}

.status-badge[data-state="error"] {
  border-color: var(--app-danger);
  background: var(--app-danger-soft);
  color: var(--app-danger);
}

.visual-metrics {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  margin: 17px 0 0;
  border-top: 1px solid var(--app-line);
  border-left: 1px solid var(--app-line);
}

.visual-metrics div {
  min-width: 0;
  padding: 8px 9px;
  border-right: 1px solid var(--app-line);
  border-bottom: 1px solid var(--app-line);
}

.visual-metrics dt {
  color: var(--app-muted);
  font-size: .72rem;
  font-weight: 760;
}

.visual-metrics dd {
  margin: 2px 0 0;
  color: var(--app-accent);
  font-size: .92rem;
  font-weight: 760;
  font-variant-numeric: tabular-nums;
  overflow-wrap: anywhere;
}

.visual-stage {
  margin-top: 15px;
}

.moon-figure {
  position: relative;
  margin: 0;
  overflow: hidden;
  border: 1px solid var(--app-line-strong);
  background: #0b1726;
}

.moon-figure[data-state="ready"] {
  border-color: var(--app-accent);
}

.moon-figure[data-state="error"] {
  border-color: var(--app-danger);
}

.moon-figure svg {
  display: block;
  width: 100%;
  height: 310px;
}

.diagram-sky {
  fill: url("#space-gradient");
}

.stars {
  fill: #dbe7ef;
  opacity: .85;
}

.orbit-ring {
  fill: none;
  stroke: #6f8798;
  stroke-dasharray: 4 7;
  stroke-width: 1.2;
  opacity: .75;
}

.sun-earth-line {
  stroke: #d8b66d;
  stroke-dasharray: 3 7;
  stroke-width: 1;
  opacity: .55;
}

.sun-moon-line {
  stroke: #d8b66d;
  stroke-width: 1.5;
  opacity: .9;
}

.earth-moon-line {
  stroke: #aac3d0;
  stroke-dasharray: 3 5;
  stroke-width: 1;
  opacity: .8;
}

.sun-glow {
  fill: #f2c46c;
  opacity: .16;
}

.sun-disc {
  fill: url("#sun-gradient");
  stroke: #ffe7a7;
  stroke-width: 1.4;
}

.earth-shadow {
  fill: #193953;
  stroke: #9bd0d5;
  stroke-width: 1.2;
}

.earth-disc {
  fill: url("#earth-gradient");
}

.earth-land {
  fill: #9bca9c;
  opacity: .8;
}

.moon-face {
  transition: transform .22s ease;
}

.moon-dark {
  fill: #3d4c5c;
  stroke: #d6e0e6;
  stroke-width: 1;
}

.moon-lit {
  fill: url("#moon-gradient");
}

.moon-crater {
  fill: #6f7e89;
  opacity: .42;
}

.moon-rim {
  fill: none;
  stroke: #edf2f4;
  stroke-width: 1.2;
  opacity: .9;
}

.diagram-labels text {
  fill: #e7eff3;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .02em;
  paint-order: stroke;
  stroke: #0b1726;
  stroke-width: 3px;
  stroke-linejoin: round;
}

#orbit-label {
  fill: #b9ccd6;
  font-size: 11px;
  font-weight: 600;
}

#diagram-hint {
  fill: #f3d28d;
  font-size: 11px;
  font-weight: 600;
}

.face-note {
  position: absolute;
  top: 10px;
  right: 10px;
  padding: 4px 8px;
  border: 1px solid rgba(231, 239, 243, .45);
  background: rgba(11, 23, 38, .78);
  color: #eef5f7;
  font-size: .72rem;
  font-weight: 700;
  line-height: 1.35;
}

.visual-caption {
  position: absolute;
  right: 10px;
  bottom: 8px;
  left: 10px;
  margin: 0;
  color: #d5e2e8;
  font-size: .72rem;
  line-height: 1.35;
  text-align: center;
  text-shadow: 0 1px 2px #0b1726;
}

.visual-description {
  margin: 12px 0 0;
  color: var(--app-muted);
  font-size: .84rem;
  overflow-wrap: anywhere;
}

.scale-note {
  margin: 6px 0 0;
  padding-left: 11px;
  border-left: 3px solid var(--app-line-strong);
  color: var(--app-muted);
  font-size: .76rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.content-section {
  margin-top: 43px;
  padding-top: 25px;
  border-top: 1px solid var(--app-line-strong);
}

.section-heading {
  margin-bottom: 15px;
}

.steps-list {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  margin: 0;
  padding: 0;
  border-block: 1px solid var(--app-line);
  list-style: none;
  counter-reset: steps;
}

.steps-list li {
  position: relative;
  min-width: 0;
  padding: 35px 12px 13px;
  border-right: 1px solid var(--app-line);
  counter-increment: steps;
  font-size: .86rem;
  overflow-wrap: anywhere;
}

.steps-list li:last-child {
  border-right: 0;
}

.steps-list li::before {
  position: absolute;
  top: 7px;
  left: 12px;
  color: var(--app-accent);
  content: counter(steps, decimal-leading-zero);
  font-size: .75rem;
  font-weight: 800;
}

.formula-list {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.formula-list article {
  display: grid;
  gap: 4px;
  min-width: 0;
  padding: 14px;
  border: 1px solid var(--app-line);
  background: var(--app-surface);
}

.formula-list strong {
  font-size: .95rem;
  overflow-wrap: anywhere;
}

.formula-list span {
  color: var(--app-muted);
  font-size: .81rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.example-box,
.phase-guide {
  margin-top: 14px;
  padding: 14px 16px;
  border: 1px solid var(--app-accent);
  background: var(--app-accent-soft);
}

.example-box h3,
.phase-guide h3 {
  color: var(--app-accent);
  font-size: .95rem;
}

.example-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 7px 18px;
  margin: 9px 0 0;
  padding-left: 1.1em;
}

.example-list li {
  padding-left: 2px;
  overflow-wrap: anywhere;
}

.example-list strong {
  margin-right: 5px;
}

.example-list span {
  color: #38413b;
  font-size: .84rem;
}

.phase-guide {
  border-color: var(--app-line);
  background: var(--app-surface);
}

.phase-guide h3 {
  color: var(--app-ink);
}

.phase-list {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 7px;
  margin: 10px 0 0;
  padding: 0;
  list-style: none;
  counter-reset: phase;
}

.phase-list li {
  display: grid;
  gap: 1px;
  min-width: 0;
  padding: 9px 10px 8px 31px;
  border: 1px solid var(--app-line);
  background: #fff;
  counter-increment: phase;
  overflow-wrap: anywhere;
}

.phase-list li::before {
  color: var(--app-accent);
  content: counter(phase, decimal-leading-zero);
  font-size: .7rem;
  font-weight: 800;
}

.phase-list strong {
  font-size: .83rem;
  line-height: 1.35;
}

.phase-list span {
  color: var(--app-muted);
  font-size: .72rem;
  line-height: 1.35;
}

.proof-guide {
  margin-top: 14px;
  padding: 16px;
  border: 1px solid var(--app-line);
  background: var(--app-surface);
}

.proof-guide ul {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0 22px;
  margin: 9px 0 0;
  padding-left: 1.2em;
  color: var(--app-muted);
  font-size: .84rem;
}

.proof-guide li {
  overflow-wrap: anywhere;
}

.proof-guide li + li {
  margin-top: 5px;
}

@media (max-width: 900px) {
  .tool-shell {
    grid-template-columns: 1fr;
  }

  .calculator-panel {
    border-right: 0;
    border-bottom: 1px solid var(--app-line);
  }

  .steps-list {
    grid-template-columns: repeat(2, 1fr);
  }

  .steps-list li:nth-child(2) {
    border-right: 0;
  }

  .steps-list li:nth-child(-n + 2) {
    border-bottom: 1px solid var(--app-line);
  }

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

@media (max-width: 760px) {
  .calculator-panel,
  .visual-panel {
    padding: 19px 18px;
  }

  .formula-list,
  .phase-list {
    grid-template-columns: 1fr 1fr;
  }

  .proof-guide ul {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 460px) {
  .calculator-panel,
  .visual-panel {
    padding: 18px 14px;
  }

  .input-wrap {
    grid-template-columns: minmax(0, 1fr) 48px;
  }

  .form-actions .button {
    flex: 1 1 140px;
  }

  .result-grid,
  .result-details,
  .visual-metrics,
  .example-list,
  .formula-list,
  .phase-list {
    grid-template-columns: 1fr;
  }

  .result-details .detail-wide {
    grid-column: auto;
  }

  .visual-heading-row {
    display: block;
  }

  .status-badge {
    display: inline-block;
    margin-top: 9px;
  }

  .moon-figure svg {
    height: 270px;
  }

  .visual-caption {
    font-size: .67rem;
  }

  .steps-list {
    grid-template-columns: 1fr;
  }

  .steps-list li,
  .steps-list li:nth-child(2) {
    border-right: 0;
    border-bottom: 1px solid var(--app-line);
  }

  .steps-list li:last-child {
    border-bottom: 0;
  }

  .phase-list li {
    grid-template-columns: 1fr;
  }
}

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

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
  }
}