/* ═══════════════════════════════════════════════════════════════════
   alex-calc v2 — Facebook-style Design
   ═══════════════════════════════════════════════════════════════════ */

/* ── CSS Custom Properties ───────────────────────────────────────── */
:root {
  --fb-blue: #1877f2;
  --fb-blue-hover: #166fe5;
  --fb-blue-dark: #1a3c6e;
  --fb-blue-light: #e7f3ff;
  --fb-bg: #f0f2f5;
  --fb-surface: #ffffff;
  --fb-surface-hover: #f2f2f2;
  --fb-border: #ced0d4;
  --fb-border-light: #e4e6eb;
  --fb-text: #050505;
  --fb-text-secondary: #65676b;
  --fb-text-muted: #8a8d91;
  --fb-success: #31a24c;
  --fb-success-light: #e8f5e9;
  --fb-error: #e41e3f;
  --fb-error-light: #fde8ea;
  --fb-warning: #f5a623;
  --fb-radius-sm: 8px;
  --fb-radius-md: 12px;
  --fb-radius-lg: 16px;
  --fb-radius-xl: 20px;
  --fb-shadow-sm: 0 1px 2px rgba(0,0,0,.1);
  --fb-shadow-md: 0 2px 8px rgba(0,0,0,.1);
  --fb-shadow-lg: 0 4px 16px rgba(0,0,0,.1);
  --fb-shadow-xl: 0 8px 24px rgba(0,0,0,.12);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --transition: 200ms cubic-bezier(.08,.52,.52,1);
}

/* ── Reset & Base ────────────────────────────────────────────────── */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--fb-bg);
  color: var(--fb-text);
  line-height: 1.34;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ── App Shell ───────────────────────────────────────────────────── */
.app {
  max-width: 1128px;
  margin: 0 auto;
  padding: 0 16px 48px;
  display: flex;
  flex-direction: column;
  gap: 0;
}

/* ── Header (Facebook-style top bar) ─────────────────────────────── */
.app-header {
  background: var(--fb-surface);
  box-shadow: var(--fb-shadow-sm);
  position: sticky;
  top: 0;
  z-index: 100;
  padding: 0;
  border-bottom: 1px solid var(--fb-border-light);
}

.header-inner {
  max-width: 1128px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
  padding: 0 16px;
}

.brand-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--fb-text);
  letter-spacing: -0.2px;
  line-height: 1.2;
}

/* ── Main Layout ─────────────────────────────────────────────────── */
.main-layout {
  display: grid;
  grid-template-columns: 1fr 360px;
  gap: 16px;
  align-items: start;
  margin-top: 16px;
}

.col-calc {
  display: flex;
  flex-direction: column;
  gap: 16px;
  min-width: 0;
}

.col-ref {
  display: flex;
  flex-direction: column;
  gap: 16px;
  position: sticky;
  top: 72px;
}

/* ── Cards (Facebook-style) ──────────────────────────────────────── */
.card {
  background: var(--fb-surface);
  border-radius: var(--fb-radius-md);
  box-shadow: var(--fb-shadow-sm);
  border: none;
  transition: box-shadow var(--transition);
  overflow: hidden;
}

.card:hover {
  box-shadow: var(--fb-shadow-md);
}

.card-header {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 16px 20px 0;
}

.card-icon {
  font-size: 16px;
  line-height: 1;
  flex-shrink: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--fb-blue-light);
  border-radius: 50%;
  color: var(--fb-blue);
}

.card-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--fb-text);
}

.card-body {
  padding: 12px 20px 20px;
}

.card-body-nopad {
  padding: 0;
}

/* ── Quick Calculator ────────────────────────────────────────────── */
.card-calc .card-body {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.form-group label {
  font-size: 13px;
  font-weight: 500;
  color: var(--fb-text-secondary);
  letter-spacing: 0;
  text-transform: none;
}

.form-group-btn {
  justify-content: flex-end;
}

/* ── Select (Facebook-style) ─────────────────────────────────────── */
.select-wrap {
  position: relative;
}

.select-wrap select {
  appearance: none;
  width: 100%;
  padding: 10px 36px 10px 14px;
  border: 1px solid var(--fb-border);
  border-radius: var(--fb-radius-sm);
  font-size: 15px;
  font-family: inherit;
  background: var(--fb-surface);
  color: var(--fb-text);
  cursor: pointer;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.select-wrap select:focus {
  outline: none;
  border-color: var(--fb-blue);
  box-shadow: 0 0 0 2px rgba(24,119,242,.2);
}

.select-chevron {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--fb-text-muted);
  pointer-events: none;
}

/* ── Input with unit ─────────────────────────────────────────────── */
.input-unit {
  display: flex;
  align-items: stretch;
}

.input-unit input {
  flex: 1;
  min-width: 0;
  padding: 10px 14px;
  border: 1px solid var(--fb-border);
  border-right: none;
  border-radius: var(--fb-radius-sm) 0 0 var(--fb-radius-sm);
  font-size: 15px;
  font-family: inherit;
  background: var(--fb-surface);
  color: var(--fb-text);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.input-unit input:focus {
  outline: none;
  border-color: var(--fb-blue);
  box-shadow: 0 0 0 2px rgba(24,119,242,.2);
  z-index: 1;
  position: relative;
}

.input-unit-label {
  display: flex;
  align-items: center;
  padding: 0 14px;
  background: var(--fb-bg);
  border: 1px solid var(--fb-border);
  border-radius: 0 var(--fb-radius-sm) var(--fb-radius-sm) 0;
  font-size: 13px;
  font-weight: 500;
  color: var(--fb-text-muted);
  white-space: nowrap;
  min-width: 48px;
  justify-content: center;
}

/* ── Price Badge ─────────────────────────────────────────────────── */
.price-badge {
  padding: 10px 14px;
  background: var(--fb-success-light);
  border: 1px solid #c8e6c9;
  border-radius: var(--fb-radius-sm);
  height: 100%;
  display: flex;
  align-items: center;
}

.price-value {
  font-size: 15px;
  font-weight: 600;
  color: #1b5e20;
}

/* ── Button (Facebook-style) ─────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 20px;
  border: none;
  border-radius: var(--fb-radius-sm);
  font-size: 15px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background var(--transition), box-shadow var(--transition), transform .1s;
  white-space: nowrap;
  user-select: none;
  line-height: 1.2;
}

.btn:active {
  transform: scale(.96);
}

.btn-primary {
  background: var(--fb-blue);
  color: #fff;
}

.btn-primary:hover {
  background: var(--fb-blue-hover);
}

.btn-secondary {
  background: var(--fb-bg);
  color: var(--fb-text-secondary);
  border: none;
}

.btn-secondary:hover {
  background: var(--fb-surface-hover);
}

.btn-sm {
  padding: 6px 14px;
  font-size: 13px;
  border-radius: var(--fb-radius-sm);
}

/* ── Result Card ─────────────────────────────────────────────────── */
.card-result {
  border: 1px solid #c8e6c9;
  background: var(--fb-success-light);
}

.card-result .card-header {
  padding-bottom: 0;
}

.result-ok .card-icon {
  background: var(--fb-success-light);
  color: var(--fb-success);
}

.result-body {
  font-size: 14px;
  color: #1b5e20;
  line-height: 1.6;
}

.result-body .result-line {
  margin-bottom: 4px;
}

.result-body .result-total {
  font-size: 17px;
  font-weight: 700;
  color: #0d3b0e;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid #c8e6c9;
}

/* ── Error Card ──────────────────────────────────────────────────── */
.card-error {
  border: 1px solid #f5c6cb;
  background: var(--fb-error-light);
}

.card-error .card-header {
  padding-bottom: 0;
}

.card-error .card-title {
  font-size: 14px;
  font-weight: 500;
  color: #a71d2a;
}

/* ── Loading ─────────────────────────────────────────────────────── */
.loading {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 24px;
  color: var(--fb-text-muted);
  font-weight: 500;
  font-size: 14px;
}

.spinner {
  width: 24px;
  height: 24px;
  border: 3px solid var(--fb-border);
  border-top-color: var(--fb-blue);
  border-radius: 50%;
  animation: spin .6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ── Accordion (Facebook-style) ──────────────────────────────────── */
.accordion {
  border-bottom: 1px solid var(--fb-border-light);
}

.accordion:last-child {
  border-bottom: none;
}

.accordion-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 16px 0;
  font-size: 15px;
  font-weight: 600;
  color: var(--fb-text);
  cursor: pointer;
  list-style: none;
  user-select: none;
  transition: background var(--transition);
  border-radius: var(--fb-radius-sm);
  margin: 0 -4px;
  padding: 12px 4px;
}

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

.accordion-summary:hover {
  background: var(--fb-bg);
}

.accordion-chevron {
  color: var(--fb-text-muted);
  flex-shrink: 0;
  transition: transform .2s;
}

.accordion[open] .accordion-chevron {
  transform: rotate(180deg);
}

.accordion-body {
  padding: 0 0 16px;
}

/* ── Form Grid (inside accordion) ────────────────────────────────── */
.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.form-grid .form-group label {
  font-size: 12px;
  font-weight: 500;
  color: var(--fb-text-secondary);
  letter-spacing: 0;
  text-transform: none;
}

.form-grid input,
.form-grid select {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--fb-border);
  border-radius: var(--fb-radius-sm);
  font-size: 14px;
  font-family: inherit;
  background: var(--fb-bg);
  color: var(--fb-text);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.form-grid input:focus,
.form-grid select:focus {
  outline: none;
  border-color: var(--fb-blue);
  box-shadow: 0 0 0 2px rgba(24,119,242,.2);
  background: var(--fb-surface);
}

/* ── Reference Table ─────────────────────────────────────────────── */
.card-ref .card-header {
  padding-bottom: 0;
}

.table-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}

thead th {
  background: var(--fb-bg);
  padding: 10px 14px;
  text-align: left;
  font-weight: 600;
  color: var(--fb-text-secondary);
  border-bottom: 1px solid var(--fb-border);
  white-space: nowrap;
  font-size: 12px;
  text-transform: none;
  letter-spacing: 0;
}

tbody td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--fb-border-light);
  color: var(--fb-text);
}

tbody tr:last-child td {
  border-bottom: none;
}

tbody tr:hover td {
  background: var(--fb-bg);
}

.table-empty {
  text-align: center;
  color: var(--fb-text-muted);
  padding: 24px 14px !important;
}

/* ── Field Error ─────────────────────────────────────────────────── */
.field-error {
  color: var(--fb-error);
  font-size: 12px;
  font-weight: 500;
  margin-top: 4px;
}

.input-error {
  border-color: var(--fb-error) !important;
  box-shadow: 0 0 0 2px rgba(228,30,63,.2) !important;
}

/* ── Result Confirmation ─────────────────────────────────────────── */
.result-confirm {
  font-size: 12px;
  color: var(--fb-success);
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px solid #c8e6c9;
}

/* ── Accordion Controls ──────────────────────────────────────────── */
.accordion-controls {
  display: flex;
  gap: 8px;
  padding: 0 0 8px;
}

/* ── Footer ──────────────────────────────────────────────────────── */
.app-footer {
  text-align: center;
  padding: 16px 0 8px;
  color: var(--fb-text-muted);
  font-size: 12px;
  border-top: 1px solid var(--fb-border-light);
  margin-top: 16px;
}

/* ── Story / Create Post style separator ─────────────────────────── */
.story-separator {
  height: 1px;
  background: var(--fb-border-light);
  margin: 0;
}

/* ═══════════════════════════════════════════════════════════════════
   Responsive — Mobile First
   ═══════════════════════════════════════════════════════════════════ */

/* ── Mobile (< 640px) ────────────────────────────────────────────── */
@media (max-width: 639px) {
  .app {
    padding: 0 0 32px;
  }

  .header-inner {
    padding: 0 12px;
    height: 48px;
  }

  .brand-title {
    font-size: 14px;
  }

  .main-layout {
    grid-template-columns: 1fr;
    gap: 12px;
    margin-top: 12px;
    padding: 0 8px;
  }

  .col-ref {
    position: static;
  }

  .card {
    border-radius: var(--fb-radius-sm);
  }

  .card-header {
    padding: 14px 14px 0;
  }

  .card-body {
    padding: 10px 14px 16px;
  }

  .form-row {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .form-grid {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .form-group-btn {
    justify-content: stretch;
  }

  .form-group-btn .btn {
    width: 100%;
  }

  .col-calc {
    gap: 12px;
  }

  .card-calc .card-body {
    gap: 10px;
  }

  .price-badge {
    min-height: 40px;
  }

  .accordion-summary {
    padding: 14px 0;
    font-size: 14px;
  }

  .accordion-body {
    padding: 0 0 14px;
  }

  .table-scroll {
    margin: 0 -14px;
  }

  table {
    font-size: 12px;
  }

  thead th,
  tbody td {
    padding: 8px 14px;
  }
}

/* ── Tablet (640px – 1023px) ─────────────────────────────────────── */
@media (min-width: 640px) and (max-width: 1023px) {
  .app {
    padding: 0 0 40px;
  }

  .main-layout {
    grid-template-columns: 1fr;
    gap: 16px;
    margin-top: 16px;
    padding: 0 16px;
  }

  .col-ref {
    position: static;
  }

  .form-grid {
    grid-template-columns: 1fr 1fr;
  }

  .card-header {
    padding: 16px 18px 0;
  }

  .card-body {
    padding: 12px 18px 18px;
  }
}

/* ── Desktop (1024px+) — already default ─────────────────────────── */

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

/* ── Dark Mode (Facebook-style dark) ─────────────────────────────── */
@media (prefers-color-scheme: dark) {
  :root {
    --fb-bg: #18191a;
    --fb-surface: #242526;
    --fb-surface-hover: #3a3b3c;
    --fb-border: #3e4042;
    --fb-border-light: #3e4042;
    --fb-text: #e4e6eb;
    --fb-text-secondary: #b0b3b8;
    --fb-text-muted: #8a8d91;
    --fb-blue: #2d88ff;
    --fb-blue-hover: #1877f2;
    --fb-blue-light: #1a3c6e;
    --fb-success: #42b72a;
    --fb-success-light: #1a3c1a;
    --fb-error: #f02849;
    --fb-error-light: #3a1c22;
    --fb-shadow-sm: 0 1px 2px rgba(0,0,0,.3);
    --fb-shadow-md: 0 2px 8px rgba(0,0,0,.4);
    --fb-shadow-lg: 0 4px 16px rgba(0,0,0,.5);
    --fb-shadow-xl: 0 8px 24px rgba(0,0,0,.6);
  }

  .price-badge {
    background: #1a3c1a;
    border-color: #2e7d32;
  }

  .price-value {
    color: #81c784;
  }

  .result-body {
    color: #81c784;
  }

  .result-body .result-total {
    color: #a5d6a7;
    border-top-color: #2e7d32;
  }

  .result-confirm {
    border-top-color: #2e7d32;
  }

  .card-icon {
    background: var(--fb-blue-light);
  }

  .input-unit-label {
    background: var(--fb-surface-hover);
  }

  .btn-secondary {
    background: var(--fb-surface-hover);
    color: var(--fb-text-secondary);
  }

  .btn-secondary:hover {
    background: #4e4f50;
  }

  .select-wrap select,
  .input-unit input,
  .form-grid input,
  .form-grid select {
    background: var(--fb-bg);
    color: var(--fb-text);
  }

  .card-result {
    border-color: #2e7d32;
  }

  .card-error {
    border-color: #7f1d1d;
  }
}