/* ============================================================
   Responsive — Mobile-First
   Breakpoints: 640px / 768px / 1024px
   ============================================================ */

/* ---- Mobile base (< 640px) ---- */
.page-main {
  padding: var(--space-6) var(--space-4);
}

.page-hero h1 {
  font-size: var(--text-3xl);
}

.calc-layout {
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

.card {
  padding: var(--space-6);
}

.result-panel .result-value {
  font-size: var(--text-3xl);
}

/* ---- Tablet (>= 640px) ---- */
@media (min-width: 640px) {
  .page-main {
    padding: var(--space-8) var(--space-6);
  }

  .page-hero h1 {
    font-size: var(--text-4xl);
  }

  .result-panel .result-value {
    font-size: var(--text-4xl);
  }
}

/* ---- Desktop (>= 768px) ---- */
@media (min-width: 768px) {
  .calc-layout {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-6);
  }

  .card {
    padding: var(--space-8);
  }

  /* Sticky results column — stays visible while scrolling inputs */
  .calc-results {
    position: sticky;
    top: 72px;
    align-self: flex-start;
  }
}

/* ---- Tablet: 2 columns for calc grid ---- */
@media (min-width: 640px) {
  .calc-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-5);
  }
}

/* ---- Desktop (>= 1024px) ---- */
@media (min-width: 1024px) {
  .page-main {
    padding: var(--space-10) var(--space-8);
  }

  /* Calculator hub: 4 columns on desktop */
  .calc-grid {
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-5);
  }
}

/* ---- Utility ---- */
@media (max-width: 639px) {
  .hide-mobile { display: none !important; }
}

@media (min-width: 640px) {
  .hide-desktop { display: none !important; }
}

/* ── Sticky result footer — mobile only ───────────────────── */
@media (max-width: 767px) {
  .sticky-result-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 90;
    background: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: var(--space-3) var(--space-6);
    box-shadow: 0 -2px 12px rgba(0, 0, 0, 0.08);
  }
  .sticky-result-label {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
  }
  .sticky-result-value {
    font-size: var(--text-lg);
    font-weight: var(--weight-bold);
    color: var(--color-text-primary);
    font-variant-numeric: tabular-nums;
  }
  /* Bottom padding so sticky footer doesn't cover content */
  .page-main {
    padding-bottom: 72px;
  }
}