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

:root {
  --color-bg: #0d1b2a;
  --color-surface: #132338;
  --color-surface-raised: #1a2e44;
  --color-border: #2a3f58;
  --color-accent: #5daece;
  --color-accent-dim: #3c7ea0;
  --color-text: #e8edf2;
  --color-text-muted: #8fa8c0;
  --color-text-hint: #5f7d96;
  --color-btn-primary: #5daece;
  --color-btn-primary-text: #0d1b2a;
  --color-warning-bg: #3d2a00;
  --color-warning-border: #c17d00;
  --color-warning-text: #f5c842;
  --color-success: #4caf80;
  --color-error: #e05555;
  --radius: 8px;
  --radius-sm: 5px;
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
}

html {
  font-size: 16px;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font);
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100dvh;
  padding-bottom: 40px;
}

/* ===== Header ===== */
header {
  background: var(--color-surface);
  border-bottom: 2px solid var(--color-accent-dim);
  padding: 12px 16px 10px;
}

.header-inner {
  max-width: 620px;
  margin: 0 auto;
}

header h1 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-accent);
  letter-spacing: 0.01em;
}

.header-sub {
  font-size: 0.72rem;
  color: var(--color-text-muted);
  margin-top: 2px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

/* ===== Navigation ===== */
nav {
  display: flex;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
  position: sticky;
  top: 0;
  z-index: 10;
}

nav::-webkit-scrollbar {
  display: none;
}

.tab-btn {
  flex: 1;
  min-width: 80px;
  padding: 12px 8px;
  background: none;
  border: none;
  border-bottom: 3px solid transparent;
  color: var(--color-text-muted);
  font-size: 0.78rem;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
  white-space: nowrap;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  -webkit-tap-highlight-color: transparent;
}

.tab-btn:hover {
  color: var(--color-text);
}

.tab-btn.active {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

/* ===== Tab Panels ===== */
.tab-panel {
  display: none;
  max-width: 620px;
  margin: 0 auto;
  padding: 20px 16px;
}

.tab-panel.active {
  display: block;
}

.tab-description {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 20px;
  line-height: 1.5;
}

/* ===== Forms ===== */
.field {
  margin-bottom: 18px;
}

.field label {
  display: block;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}

.field input[type="number"],
.field input[type="text"] {
  width: 100%;
  padding: 12px 14px;
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-size: 1rem;
  font-family: var(--font);
  transition: border-color 0.15s;
  -webkit-appearance: none;
  appearance: none;
}

.field input[type="number"]:focus,
.field input[type="text"]:focus {
  outline: none;
  border-color: var(--color-accent);
}

.field input[type="number"]::placeholder {
  color: var(--color-text-hint);
}

/* Remove number input spinners */
.field input[type="number"]::-webkit-inner-spin-button,
.field input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  appearance: none;
}
.field input[type="number"] {
  -moz-appearance: textfield;
}

.field-hint {
  display: block;
  font-size: 0.73rem;
  color: var(--color-text-hint);
  margin-top: 5px;
}

.field-note {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: -10px;
  margin-bottom: 18px;
  font-style: italic;
}

.field-error {
  display: block;
  font-size: 0.78rem;
  color: var(--color-error);
  margin-top: 5px;
  min-height: 1em;
}

/* ===== Toggle Buttons (serving size) ===== */
.toggle-group {
  display: flex;
  gap: 8px;
  margin-top: 4px;
}

.toggle-btn {
  flex: 1;
  padding: 11px 12px;
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  font-size: 0.95rem;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.toggle-btn:hover {
  border-color: var(--color-accent-dim);
  color: var(--color-text);
}

.toggle-btn.active {
  background: var(--color-accent-dim);
  border-color: var(--color-accent);
  color: var(--color-text);
}

/* ===== Buttons ===== */
.btn-primary {
  width: 100%;
  padding: 14px;
  background: var(--color-btn-primary);
  border: none;
  border-radius: var(--radius-sm);
  color: var(--color-btn-primary-text);
  font-size: 1rem;
  font-weight: 700;
  font-family: var(--font);
  cursor: pointer;
  letter-spacing: 0.03em;
  transition: opacity 0.15s;
  margin-top: 4px;
  -webkit-tap-highlight-color: transparent;
}

.btn-primary:hover {
  opacity: 0.88;
}

.btn-primary:active {
  opacity: 0.75;
}

.btn-row {
  display: flex;
  gap: 10px;
  margin-top: 4px;
}

.btn-row .btn-primary {
  margin-top: 0;
}

.btn-secondary {
  flex: 1;
  padding: 14px;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  font-size: 1rem;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.btn-secondary:hover {
  border-color: var(--color-accent-dim);
  color: var(--color-text);
}

/* ===== Results Panel ===== */
.results-panel {
  margin-top: 28px;
}

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

.result-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 12px 14px;
}

.result-card.primary {
  border-color: var(--color-accent-dim);
  background: var(--color-surface-raised);
}

.result-label {
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 5px;
}

.result-value {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-accent);
  line-height: 1.2;
}

.result-card.primary .result-value {
  font-size: 1.6rem;
}

.result-sub {
  font-size: 0.77rem;
  color: var(--color-text-muted);
  margin-top: 3px;
}

/* Full-width card variant */
.result-card.full {
  grid-column: 1 / -1;
}

/* ===== Warning / Alert Banners ===== */
.alert-warning {
  background: var(--color-warning-bg);
  border: 1px solid var(--color-warning-border);
  border-radius: var(--radius-sm);
  color: var(--color-warning-text);
  font-size: 0.85rem;
  line-height: 1.5;
  padding: 12px 14px;
  margin-bottom: 16px;
}

.alert-warning strong {
  display: block;
  margin-bottom: 3px;
}

/* ===== Settings ===== */
.settings-saved {
  font-size: 0.85rem;
  color: var(--color-success);
  margin-top: 12px;
  text-align: center;
}

/* ===== Responsive: widen on larger screens ===== */
@media (max-width: 420px) {
  .results-grid {
    grid-template-columns: 1fr;
  }

  .result-card.full {
    grid-column: 1;
  }

  nav {
    justify-content: flex-start;
  }

  .tab-btn {
    font-size: 0.72rem;
    padding: 12px 6px;
  }
}

@media (min-width: 480px) {
  .tab-panel {
    padding: 24px 20px;
  }

  header {
    padding: 14px 20px 12px;
  }

  header h1 {
    font-size: 1.3rem;
  }
}

/* ===== Site Header (landing page) ===== */
.site-header {
  background: var(--color-surface);
  border-bottom: 2px solid var(--color-accent-dim);
  padding: 12px 16px;
}

.site-header-inner {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.site-brand-name {
  display: block;
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-accent);
  letter-spacing: 0.01em;
}

.site-brand-sub {
  display: block;
  font-size: 0.68rem;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-top: 2px;
}

.site-header-cta {
  flex-shrink: 0;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--color-accent);
  text-decoration: none;
  border: 1px solid var(--color-accent-dim);
  border-radius: var(--radius-sm);
  padding: 7px 14px;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.site-header-cta:hover {
  background: var(--color-accent-dim);
  color: var(--color-text);
}

/* ===== Hero ===== */
.hero {
  padding: 60px 16px 56px;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
}

.hero-inner {
  max-width: 540px;
  margin: 0 auto;
}

.hero-eyebrow {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-accent-dim);
  margin-bottom: 20px;
}

.hero-headline {
  font-size: 2.75rem;
  font-weight: 800;
  color: var(--color-text);
  line-height: 1.08;
  letter-spacing: -0.025em;
  margin-bottom: 22px;
}

.hero-accent {
  color: var(--color-accent);
}

.hero-sub {
  font-size: 0.975rem;
  color: var(--color-text-muted);
  line-height: 1.65;
  margin-bottom: 36px;
  max-width: 460px;
  margin-left: auto;
  margin-right: auto;
}

.hero-btn {
  display: inline-block;
  padding: 15px 30px;
  background: var(--color-accent);
  color: var(--color-bg);
  font-size: 0.95rem;
  font-weight: 700;
  font-family: var(--font);
  text-decoration: none;
  border-radius: var(--radius-sm);
  letter-spacing: 0.02em;
  transition: opacity 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.hero-btn:hover {
  opacity: 0.88;
}

@media (min-width: 480px) {
  .hero {
    padding: 80px 20px 72px;
  }
  .hero-headline {
    font-size: 3.5rem;
  }
}

/* ===== Features ===== */
.features {
  padding: 44px 16px 40px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
}

.features-inner {
  max-width: 760px;
  margin: 0 auto;
}

.features-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-hint);
  text-align: center;
  margin-bottom: 22px;
}

.features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin-bottom: 28px;
}

@media (min-width: 600px) {
  .features-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.feature-card {
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 22px 20px;
}

.feature-num {
  display: block;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--color-accent);
  opacity: 0.55;
  margin-bottom: 10px;
}

.feature-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 10px;
}

.feature-card p {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

.features-cta-row {
  text-align: center;
}

.features-cta {
  display: inline-block;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--color-text-muted);
  text-decoration: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 11px 22px;
  transition: border-color 0.15s, color 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.features-cta:hover {
  border-color: var(--color-accent-dim);
  color: var(--color-accent);
}

/* ===== Calculator back link ===== */
.app-header-row {
  display: flex;
  align-items: center;
  gap: 14px;
}

.back-link {
  font-size: 1.4rem;
  line-height: 1;
  color: var(--color-text-muted);
  text-decoration: none;
  flex-shrink: 0;
  transition: color 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.back-link:hover {
  color: var(--color-accent);
}

/* ===== Shared Section Layout ===== */
.how-to-use,
.products-section {
  padding: 32px 16px 36px;
}

.how-to-use {
  border-top: 1px solid var(--color-border);
}

.products-section {
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
}

.section-inner {
  max-width: 620px;
  margin: 0 auto;
}

.section-heading {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 6px;
}

.section-sub {
  font-size: 0.84rem;
  color: var(--color-text-muted);
  line-height: 1.5;
  margin-bottom: 22px;
}

/* ===== How to Use ===== */
.how-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
  margin-bottom: 10px;
}

@media (min-width: 540px) {
  .how-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.how-card {
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 16px;
}

.how-card-title {
  font-size: 0.73rem;
  font-weight: 700;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 8px;
}

.how-card p {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  line-height: 1.55;
}

.how-tips {
  background: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin-top: 10px;
}

.how-tips-title {
  font-size: 0.73rem;
  font-weight: 700;
  color: var(--color-text);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 14px;
}

.how-tips ul {
  list-style: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.how-tips li {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  line-height: 1.55;
  padding-left: 18px;
  position: relative;
}

.how-tips li::before {
  content: '—';
  position: absolute;
  left: 0;
  color: var(--color-accent-dim);
  font-size: 0.78rem;
  top: 1px;
}

.how-tips li strong {
  color: var(--color-text);
  font-weight: 600;
}

/* ===== Products ===== */
.products-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
}

@media (min-width: 480px) {
  .products-grid {
    grid-template-columns: 1fr 1fr;
  }
}

.product-card {
  display: flex;
  flex-direction: column;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 16px;
  text-decoration: none;
  transition: border-color 0.15s, background 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.product-card:hover {
  border-color: var(--color-accent-dim);
  background: var(--color-surface-raised);
}

.product-badge {
  display: inline-block;
  font-size: 0.63rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent);
  border: 1px solid var(--color-accent-dim);
  border-radius: 3px;
  padding: 2px 7px;
  margin-bottom: 10px;
  width: fit-content;
}

.product-card h3 {
  font-size: 0.93rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 8px;
  line-height: 1.3;
}

.product-card p {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  line-height: 1.55;
  flex: 1;
  margin-bottom: 14px;
}

.product-cta {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--color-accent);
  letter-spacing: 0.02em;
}

/* ===== Footer ===== */
footer {
  border-top: 1px solid var(--color-border);
  padding: 18px 16px;
  text-align: center;
}

.footer-inner {
  max-width: 620px;
  margin: 0 auto;
}

footer p {
  font-size: 0.75rem;
  color: var(--color-text-hint);
  line-height: 1.6;
}

footer a {
  color: var(--color-text-muted);
  text-decoration: none;
}

footer a:hover {
  color: var(--color-accent);
}

/* ===== Print ===== */
@media print {
  header, nav, form, .btn-primary, .btn-secondary,
  .site-header, .hero, .features, .how-to-use, .products-section, footer { display: none; }
  .tab-panel { display: block; }
  .results-panel { margin-top: 0; }
}