/* ---------------------------------------------------------------------------
   Global design tokens — colors and spacing for a restrained, readable UI.
   --------------------------------------------------------------------------- */
:root {
  --bg: #e8eaee;
  --surface: #ffffff;
  --border: #c5cad3;
  --text: #1c1f26;
  --muted: #5a6270;
  --accent: #1f4a6e;
  --accent-soft: #e8f0f7;
  --copper: #b87333;
  --danger-bg: #fdeaea;
  --danger-border: #e0a4a4;
  --danger-text: #6b1c1c;
  --warn-bg: #fff8e6;
  --warn-border: #e0c97a;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(28, 31, 38, 0.08);
  --font: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
}

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

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.55;
  color: var(--text);
  background: var(--bg);
  padding: 1.5rem 1rem 3rem;
}

/* Page width — comfortable reading width for forms and numeric output. */
.page {
  max-width: 42rem;
  margin: 0 auto;
}

/* Header block under the title. */
.app-header {
  margin-bottom: 0.45rem;
}

.eyebrow {
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.2rem;
}

.app-header h1 {
  font-size: 1.5rem;
  font-weight: 650;
  line-height: 1.2;
  margin: 0 0 0.3rem;
  color: var(--accent);
}

.lede {
  margin: 0;
  color: var(--muted);
  font-size: 0.8rem;
  line-height: 1.35;
  max-width: 36rem;
}

.design-basis {
  margin: 0 0 0.25rem;
  font-size: 0.78rem;
  color: var(--text);
  max-width: 36rem;
  line-height: 1.35;
}

.app-header p + p {
  margin-top: 0.2rem;
}

.app-header .design-basis {
  margin-bottom: 0;
}

/* Cards wrap major sections (inputs + results). */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 0.9rem 1rem 1rem;
  margin-bottom: 1rem;
}

.card--inputs {
  padding: 0.6rem 0.85rem 0.7rem;
}

.card--inputs .card-title {
  margin: 0 0 0.4rem;
  font-size: 1rem;
}

.card--inputs .fieldset-label {
  margin: 0.4rem 0 0.2rem;
  padding-bottom: 0.08rem;
}

.card--inputs .fieldset-label:first-of-type {
  margin-top: 0;
}

.card--inputs .grid-inputs {
  gap: 0.2rem 0.55rem;
}

.card--inputs .field {
  gap: 0.06rem;
}

.card--inputs .field label {
  font-size: 0.8rem;
  line-height: 1.15;
}

/* Keep selects aligned when a label wraps (e.g. double-shear side member). */
.card--inputs .grid-inputs--config .field label,
.card--inputs .grid-inputs--geometry .field label {
  min-height: 2.3em;
  display: block;
}

.card--inputs .field input,
.card--inputs .field select {
  padding: 0.26rem 0.42rem;
  font-size: 0.88rem;
}

.card--inputs .field--factor .factor-value {
  font-weight: 600;
}

.card--inputs .field--factor .factor-value--locked {
  background: var(--accent-soft);
  color: var(--accent);
}

.card--inputs .field--factor .factor-preset {
  margin-top: 0.15rem;
  font-size: 0.72rem;
  color: var(--muted);
}

.card--inputs .grid-inputs--factors .field label .unit {
  display: block;
  font-size: 0.65rem;
  font-weight: 400;
  text-transform: none;
  letter-spacing: 0;
}

.card--inputs .config-hint {
  margin: 0.1rem 0 0;
  font-size: 0.68rem;
  line-height: 1.2;
}

.card--inputs .actions {
  margin-top: 0.55rem;
  padding-top: 0.45rem;
}

.card--inputs button[type="submit"],
.card--inputs button#btn-calculate {
  padding: 0.42rem 1.1rem;
  font-size: 0.88rem;
}

.card--results {
  border-top: 3px solid var(--accent);
}

.card-title {
  font-size: 1.05rem;
  margin: 0 0 0.75rem;
  color: var(--accent);
}

/* Subheadings inside the form. */
.fieldset-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  margin: 0.85rem 0 0.5rem;
  padding-bottom: 0.2rem;
  border-bottom: 1px solid var(--border);
}

.fieldset-label:first-of-type {
  margin-top: 0;
}

.hint {
  font-weight: 400;
  text-transform: none;
  letter-spacing: 0;
  font-size: 0.7rem;
  color: var(--muted);
}

/* Responsive grid for numeric fields. */
.grid-inputs {
  display: grid;
  gap: 0.55rem 0.75rem;
  grid-template-columns: 1fr;
}

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

.grid-inputs--geometry {
  grid-template-columns: repeat(3, 1fr);
}

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

@media (min-width: 34rem) {
  .grid-inputs {
    grid-template-columns: repeat(3, 1fr);
  }

  .grid-inputs--config {
    grid-template-columns: repeat(5, 1fr);
  }

  .grid-inputs--geometry {
    grid-template-columns: repeat(3, 1fr);
  }

  .grid-inputs--factors {
    grid-template-columns: repeat(4, 1fr);
  }

  .grid-inputs--wide {
    grid-template-columns: 1fr 1fr;
  }
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.field--span {
  grid-column: 1 / -1;
}

.field label {
  font-size: 0.9rem;
  font-weight: 500;
}

.unit {
  color: var(--muted);
  font-weight: 400;
  font-size: 0.85rem;
}

.field input,
.field select {
  width: 100%;
  max-width: 100%;
  padding: 0.38rem 0.5rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  font: inherit;
  background: #fafbfc;
}

.field input.field__input--locked {
  background: #eef1f4;
  color: var(--muted);
  cursor: not-allowed;
  pointer-events: none;
}

.field input:focus,
.field select:focus {
  outline: 2px solid var(--accent-soft);
  border-color: var(--accent);
}

.microhint {
  font-size: 0.75rem;
  color: var(--muted);
  margin-top: 0.1rem;
}

.config-hint {
  font-size: 0.75rem;
  color: var(--muted);
  margin: 0.35rem 0 0;
  line-height: 1.4;
}

.actions {
  margin-top: 1.35rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

button[type="submit"],
button#btn-calculate {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.55rem 1.35rem;
  border-radius: 6px;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
}

button[type="submit"]:hover,
button#btn-calculate:hover {
  filter: brightness(1.05);
}

/* Alerts: prominent disclaimer and softer reminder. */
.alert {
  border-radius: var(--radius);
  padding: 0.5rem 0.7rem;
  font-size: 0.78rem;
  margin: 0 0 0.65rem;
  line-height: 1.35;
}

.alert--critical {
  background: var(--danger-bg);
  border: 1px solid var(--danger-border);
  color: var(--danger-text);
}

.alert--soft {
  background: var(--warn-bg);
  border: 1px solid var(--warn-border);
  color: #5c4a1a;
  margin-top: 1rem;
  margin-bottom: 0;
}

/* Results: large numbers and explanatory footnotes. */
.result-block {
  margin-bottom: 1.15rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.result-block:last-of-type {
  border-bottom: none;
  padding-bottom: 0;
  margin-bottom: 0;
}

.result-label {
  display: block;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

.result-value {
  display: block;
  font-size: 1.75rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--accent);
  letter-spacing: -0.02em;
}

.result-formula {
  margin: 0.35rem 0 0;
  font-size: 0.78rem;
  color: var(--muted);
  line-height: 1.4;
  word-break: break-word;
}

.mono {
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.92em;
}

.calc-trace {
  margin-top: 0.35rem;
}

.calc-step {
  background: var(--bg);
  border-radius: 6px;
  padding: 0.35rem 0.55rem;
  margin-bottom: 0.35rem;
  font-size: 0.8rem;
}

.calc-step__summary {
  cursor: pointer;
  font-weight: 600;
  list-style: none;
  display: flex;
  justify-content: space-between;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.calc-step__summary::-webkit-details-marker {
  display: none;
}

.calc-step__result-inline {
  color: var(--copper);
  font-weight: 600;
  font-size: 0.82rem;
  white-space: nowrap;
}

.calc-step__formula {
  margin: 0.3rem 0;
  color: var(--muted);
  line-height: 1.4;
  word-break: break-word;
}

.calc-step__vars {
  margin: 0.25rem 0 0;
  padding-left: 1rem;
  font-size: 0.78rem;
  color: var(--text);
}

.calc-step__ref {
  margin: 0.25rem 0 0;
  font-size: 0.75rem;
  font-style: italic;
  color: var(--muted);
}

.calc-trace__warnings {
  margin: 0.5rem 0 0;
  padding-left: 1.1rem;
  font-size: 0.82rem;
  color: var(--danger-text);
}

.result-foot {
  margin: 0.45rem 0 0;
  font-size: 0.82rem;
  color: var(--muted);
}

.result-block--notes .notes-body {
  margin: 0.35rem 0 0;
  font-size: 0.9rem;
  color: var(--text);
  white-space: pre-line;
}

.footer {
  text-align: center;
  font-size: 0.82rem;
  color: var(--muted);
}

.footer code {
  font-size: 0.88em;
  background: rgba(0, 0, 0, 0.05);
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
}

.report-hint {
  margin: 0.35rem 0 0;
  font-size: 0.85rem;
  color: var(--muted);
}

.btn-row {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.65rem;
  flex-wrap: wrap;
}

.btn {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.45rem 0.85rem;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.88rem;
  font-family: inherit;
}

.btn:hover {
  filter: brightness(1.05);
}

.btn--secondary {
  background: var(--muted);
}