: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-blue: #315f73;
  --app-blue-soft: #e4edf0;
  --app-warm: #a36b35;
  --app-warm-soft: #f1e7d9;
  --app-danger: #9b2f2f;
  --app-danger-soft: #f8e9e7;
}

* {
  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-grid,
.mode-options,
.result-details,
.visual-metrics,
.formula-list,
.figure-card {
  min-width: 0;
}

.tool-shell {
  display: grid;
  grid-template-columns: minmax(0, 0.92fr) minmax(0, 1.08fr);
  border: 1px solid var(--app-line-strong);
  background: var(--app-surface);
}

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

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

.section-heading {
  margin-bottom: 17px;
}

.section-kicker {
  margin: 0 0 5px;
  color: var(--app-accent);
  font-size: 0.76rem;
  font-weight: 780;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

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

h3 {
  margin: 0;
  font-size: 0.98rem;
  line-height: 1.45;
}

.mode-fieldset {
  margin: 0;
  padding: 0;
  border: 0;
}

.mode-fieldset legend {
  margin-bottom: 9px;
  font-size: 0.84rem;
  font-weight: 760;
}

.mode-options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 7px;
}

.mode-option {
  position: relative;
  display: block;
  cursor: pointer;
}

.mode-option input {
  position: absolute;
  opacity: 0;
}

.mode-option span {
  display: grid;
  min-height: 52px;
  place-items: center;
  padding: 8px 9px;
  border: 1px solid var(--app-line);
  background: var(--app-panel);
  color: var(--app-muted);
  font-size: 0.82rem;
  font-weight: 740;
  line-height: 1.4;
  text-align: center;
  overflow-wrap: anywhere;
}

.mode-option input:checked + span {
  border-color: var(--app-accent);
  background: var(--app-accent-soft);
  color: var(--app-accent);
}

.mode-option input:focus-visible + span {
  outline: 3px solid var(--app-accent);
  outline-offset: 2px;
}

.input-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 15px 13px;
  margin-top: 19px;
}

.field-group {
  min-width: 0;
}

.field-group-wide {
  grid-column: 1 / -1;
}

.field-group label {
  display: block;
  margin-bottom: 5px;
  font-size: 0.84rem;
  font-weight: 760;
  line-height: 1.45;
}

.input-with-unit {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  min-width: 0;
}

.field-group 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-with-unit input {
  border-right: 0;
}

.unit {
  display: grid;
  min-width: 66px;
  place-items: center;
  padding: 0 10px;
  border: 1px solid var(--app-line-strong);
  background: var(--app-surface);
  color: var(--app-muted);
  font-size: 0.78rem;
  font-weight: 760;
  white-space: nowrap;
}

.field-group input:focus {
  position: relative;
  z-index: 1;
  border-color: var(--app-accent);
  outline: 3px solid var(--app-accent-soft);
  outline-offset: 0;
}

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

.field-help,
.field-error,
.form-note {
  margin: 5px 0 0;
  color: var(--app-muted);
  font-size: 0.73rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.field-error {
  color: var(--app-danger);
  font-weight: 700;
}

.field-error:empty {
  display: none;
}

.form-note {
  margin-top: 17px;
  padding: 10px 12px;
  border-left: 3px solid var(--app-warm);
  background: var(--app-warm-soft);
  color: var(--app-ink);
}

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

.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: 0.84rem;
  font-weight: 700;
  overflow-wrap: anywhere;
}

.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);
}

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

.result-label,
.result-status {
  margin: 0;
}

.result-label {
  color: var(--app-muted);
  font-size: 0.78rem;
  font-weight: 760;
}

.result-value {
  display: block;
  margin-top: 2px;
  color: var(--app-accent);
  font-size: clamp(1.42rem, 3vw, 1.95rem);
  font-weight: 820;
  line-height: 1.35;
  overflow-wrap: anywhere;
}

.result-status {
  margin-top: 4px;
  color: var(--app-muted);
  font-size: 0.82rem;
  overflow-wrap: anywhere;
}

.result-details {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 16px 0 0;
  border-top: 1px solid var(--app-line);
  border-left: 1px solid var(--app-line);
}

.result-details > div {
  min-width: 0;
  padding: 9px 10px;
  border-right: 1px solid var(--app-line);
  border-bottom: 1px solid var(--app-line);
}

.result-details dt,
.visual-metrics dt {
  color: var(--app-muted);
  font-size: 0.72rem;
  line-height: 1.4;
}

.result-details dd,
.visual-metrics dd {
  margin: 3px 0 0;
  font-size: 0.81rem;
  font-weight: 740;
  line-height: 1.5;
  overflow-wrap: anywhere;
}

.direction-note {
  margin: 14px 0 0;
  padding: 10px 11px;
  border-left: 4px solid var(--app-blue);
  background: var(--app-blue-soft);
  color: var(--app-ink);
  font-size: 0.78rem;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

.visual-heading-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.status-badge {
  flex: 0 0 auto;
  padding: 4px 8px;
  border: 1px solid var(--app-line-strong);
  color: var(--app-muted);
  font-size: 0.72rem;
  font-weight: 760;
  line-height: 1.45;
  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(2, minmax(0, 1fr));
  margin: 19px 0 0;
  border-top: 1px solid var(--app-line);
  border-left: 1px solid var(--app-line);
}

.visual-metrics > div {
  min-width: 0;
  padding: 10px;
  border-right: 1px solid var(--app-line);
  border-bottom: 1px solid var(--app-line);
}

.figure-card {
  margin: 17px 0 0;
  padding: 12px;
  border: 1px solid var(--app-line);
  background: #f1f3ee;
}

.figure-card h3 {
  margin-bottom: 8px;
}

.figure-card svg {
  display: block;
  width: 100%;
  height: auto;
  margin: 0 auto;
}

.figure-card figcaption {
  margin-top: 9px;
  color: var(--app-muted);
  font-size: 0.73rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.orbit-track {
  fill: none;
  stroke: var(--app-line-strong);
  stroke-width: 2;
  stroke-dasharray: 5 5;
}

.reference-axis {
  stroke: var(--app-line);
  stroke-width: 1.5;
}

.radius-line {
  stroke: var(--app-accent);
  stroke-width: 3;
}

.angle-arc {
  fill: none;
  stroke: var(--app-warm);
  stroke-width: 4;
  stroke-linecap: round;
}

.moving-object {
  fill: #d6a347;
  stroke: #7f5e29;
  stroke-width: 2.5;
}

.velocity-arrow {
  stroke: var(--app-blue);
  stroke-width: 4;
  stroke-linecap: round;
}

.inward-arrow {
  stroke: var(--app-danger);
  stroke-width: 4;
  stroke-linecap: round;
}

.diagram-label {
  fill: var(--app-ink);
  font-size: 13px;
  font-weight: 740;
}

.diagram-label-muted {
  fill: var(--app-muted);
  font-size: 11px;
  font-weight: 650;
}

.diagram-label-velocity {
  fill: var(--app-blue);
}

.diagram-label-inward {
  fill: var(--app-danger);
}

.diagram-label-angle {
  fill: #7b4c20;
}

.visual-description,
.scale-note {
  margin: 13px 0 0;
  color: var(--app-ink);
  font-size: 0.82rem;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

.scale-note {
  margin-top: 6px;
  color: var(--app-muted);
  font-size: 0.73rem;
}

.content-section {
  margin-top: 43px;
}

.formula-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-top: 17px;
  border-top: 1px solid var(--app-line);
  border-left: 1px solid var(--app-line);
}

.formula-list article {
  display: grid;
  gap: 4px;
  min-width: 0;
  padding: 14px 15px;
  border-right: 1px solid var(--app-line);
  border-bottom: 1px solid var(--app-line);
}

.formula-list strong {
  font-size: 1rem;
  line-height: 1.55;
  overflow-wrap: anywhere;
}

.formula-list span {
  color: var(--app-muted);
  font-size: 0.81rem;
}

.proof-guide {
  margin-top: 20px;
  padding: 17px 18px;
  border: 1px solid var(--app-line);
  background: var(--app-surface);
}

.proof-guide ul {
  margin: 10px 0 0;
  padding-left: 1.25em;
}

.proof-guide li {
  margin-top: 5px;
  overflow-wrap: anywhere;
}

@media (max-width: 880px) {
  .tool-shell {
    grid-template-columns: 1fr;
  }

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

@media (max-width: 560px) {
  .calculator-panel,
  .visual-panel {
    padding: 19px 14px;
  }

  .input-grid,
  .result-details,
  .formula-list {
    grid-template-columns: 1fr;
  }

  .field-group-wide {
    grid-column: auto;
  }

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

  .diagram-label {
    font-size: 18px;
  }

  .diagram-label-muted {
    font-size: 15px;
  }
}

@media (max-width: 360px) {
  .mode-options,
  .visual-metrics {
    grid-template-columns: 1fr;
  }

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

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