/* styles.css — Fifth Key. Mobile-first, usable at 375px. Dark mode via
   prefers-color-scheme, safe-area insets via env(), tap targets ≥ 44px. */

:root {
  --bg: #f4f6f8;
  --surface: #ffffff;
  --surface-2: #eef1f4;
  --text: #16202a;
  --muted: #5c6b7a;
  --border: #d6dde4;
  --accent: #0e7c86;
  --accent-ink: #ffffff;
  --result-bg: #e3f4f4;
  --result-text: #0b5b63;
  --pay: #b23a48;
  --receive: #1f7a4d;
  --radius: 14px;
  --tap: 44px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101418;
    --surface: #1a2027;
    --surface-2: #222a33;
    --text: #e7edf2;
    --muted: #9aa7b3;
    --border: #303a45;
    --accent: #2bb3bf;
    --accent-ink: #06222420;
    --result-bg: #123037;
    --result-text: #7fe3ec;
    --pay: #ef8a94;
    --receive: #74d69f;
  }
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, system-ui, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.45;
  padding:
    env(safe-area-inset-top)
    env(safe-area-inset-right)
    env(safe-area-inset-bottom)
    env(safe-area-inset-left);
}

.app {
  max-width: 560px;
  margin: 0 auto;
  padding: 16px 16px 48px;
}

header {
  padding: 8px 2px 12px;
}

header h1 {
  margin: 0;
  font-size: 1.5rem;
  letter-spacing: -0.01em;
}

header p {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

/* Tabs */
.tabs {
  display: flex;
  gap: 6px;
  background: var(--surface-2);
  padding: 4px;
  border-radius: var(--radius);
  margin: 8px 0 18px;
}

.tab {
  flex: 1;
  min-height: var(--tap);
  border: 0;
  border-radius: 10px;
  background: transparent;
  color: var(--muted);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
}

.tab[aria-selected="true"] {
  background: var(--surface);
  color: var(--text);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12);
}

.panel {
  display: block;
}

.panel[hidden] {
  display: none;
}

/* Solve fields */
.field {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  margin-bottom: 10px;
}

.field.is-target {
  border-color: var(--accent);
  background: var(--result-bg);
}

.field-head {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
}

.field-name {
  font-weight: 600;
}

.field-key {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--muted);
  background: var(--surface-2);
  border-radius: 6px;
  padding: 2px 6px;
}

.solve-btn {
  margin-left: auto;
  min-height: 32px;
  padding: 4px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
}

.field.is-target .solve-btn {
  background: var(--accent);
  color: var(--accent-ink);
  border-color: var(--accent);
}

.field-input {
  display: flex;
  gap: 8px;
  align-items: stretch;
}

input,
select {
  font-size: 1rem;
  min-height: var(--tap);
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
  color: var(--text);
  width: 100%;
}

input:focus,
select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

.field-input .mag {
  flex: 2;
}

.field-input .dir {
  flex: 3;
}

.field-input .suffix {
  align-self: center;
  color: var(--muted);
  font-size: 0.85rem;
  white-space: nowrap;
}

/* Result value inside a target field */
.field-result {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--result-text);
}

.field-result .dir-word {
  display: block;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--muted);
  margin-top: 2px;
}

.field-result.is-error {
  font-size: 1rem;
  font-weight: 600;
  color: var(--pay);
}

/* Advanced */
details.advanced,
details.amort {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin: 8px 0;
  padding: 0 14px;
}

details.advanced[open],
details.amort[open] {
  padding-bottom: 12px;
}

summary {
  min-height: var(--tap);
  display: flex;
  align-items: center;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  content: "▾";
  margin-left: auto;
  color: var(--muted);
}

details[open] > summary::after {
  content: "▴";
}

.advanced-body {
  display: grid;
  gap: 12px;
  padding-top: 4px;
}

.advanced-body label {
  display: grid;
  gap: 4px;
  font-size: 0.9rem;
  color: var(--muted);
}

/* Summary sentence */
.summary {
  background: var(--surface-2);
  border-radius: var(--radius);
  padding: 14px 16px;
  margin: 10px 0;
  font-size: 1.02rem;
}

.summary:empty {
  display: none;
}

/* Amortization table */
.amort-table {
  width: 100%;
  border-collapse: collapse;
  font-variant-numeric: tabular-nums;
  font-size: 0.86rem;
}

.amort-table th,
.amort-table td {
  padding: 7px 6px;
  text-align: right;
  border-bottom: 1px solid var(--border);
}

.amort-table th:first-child,
.amort-table td:first-child {
  text-align: left;
}

.amort-table tfoot td {
  font-weight: 700;
  border-bottom: 0;
}

/* Cash flows */
.rate-row {
  display: grid;
  gap: 6px;
  font-size: 0.9rem;
  color: var(--muted);
  margin-bottom: 14px;
}

.flow-row {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 8px;
}

.flow-year {
  flex: 0 0 auto;
  min-width: 58px;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--muted);
}

.flow-row .mag {
  flex: 2;
}

.flow-row .dir {
  flex: 2;
}

.flow-remove {
  flex: 0 0 auto;
  width: var(--tap);
  height: var(--tap);
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
  color: var(--pay);
  font-size: 1.2rem;
  cursor: pointer;
}

.add {
  width: 100%;
  min-height: var(--tap);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--accent);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  margin-top: 4px;
}

.cash-results {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 18px;
}

.metric {
  background: var(--result-bg);
  border-radius: var(--radius);
  padding: 14px;
  text-align: center;
}

.metric-label {
  display: block;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--muted);
  text-transform: uppercase;
}

.metric-value {
  display: block;
  margin-top: 6px;
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--result-text);
}

.metric-value.is-error {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--muted);
}

.note {
  color: var(--muted);
  font-size: 0.85rem;
  margin: 4px 2px 0;
}