/* =====================================================
   BMI Dashboard — Production Stylesheet
   Design: Premium Health App, Soft & Modern
   ===================================================== */

/* =====================================================
   1. CSS RESET & BOX-SIZING
   ===================================================== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
svg,
canvas {
  display: block;
  max-width: 100%;
}

button,
input,
select,
textarea {
  font: inherit;
  border: 0;
  background: none;
}

button {
  cursor: pointer;
}

a {
  color: inherit;
  text-decoration: none;
}

ul,
ol {
  list-style: none;
}

h1, h2, h3, h4, h5, h6 {
  line-height: 1.25;
}

/* =====================================================
   2. CSS CUSTOM PROPERTIES (DESIGN TOKENS)
   ===================================================== */
:root {
  /* Brand Colors */
  --primary:          #4A90E2;
  --primary-dark:     #3478C8;
  --primary-light:    #EBF4FF;
  --primary-alpha:    rgba(74, 144, 226, 0.12);

  /* Semantic Colors */
  --success:          #52C41A;
  --success-light:    #F6FFED;
  --warning:          #FAAD14;
  --warning-light:    #FFFBE6;
  --danger:           #FF4D4F;
  --danger-light:     #FFF1F0;
  --info:             #1890FF;
  --info-light:       #E6F7FF;

  /* Backgrounds */
  --bg-light:         #F0F4F8;
  --bg-lighter:       #E8EDF2;
  --bg-white:         #FFFFFF;
  --bg-dark:          #2D3748;

  /* Text */
  --text-dark:        #2D3748;
  --text-medium:      #4A5568;
  --text-muted:       #718096;
  --text-light:       #A0AEC0;
  --text-white:       #FFFFFF;

  /* Cards & Surfaces */
  --card-bg:          #FFFFFF;
  --card-border:      #E2E8F0;

  /* Shape & Spacing */
  --border-radius:    12px;
  --border-radius-sm: 8px;
  --border-radius-lg: 20px;
  --border-radius-xl: 32px;
  --border-radius-pill: 999px;

  /* Shadows */
  --shadow-sm:        0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow:           0 4px 16px rgba(0,0,0,0.07), 0 2px 6px rgba(0,0,0,0.04);
  --shadow-md:        0 8px 24px rgba(0,0,0,0.09), 0 4px 8px rgba(0,0,0,0.05);
  --shadow-lg:        0 16px 40px rgba(0,0,0,0.12), 0 8px 16px rgba(0,0,0,0.06);
  --shadow-primary:   0 4px 14px rgba(74, 144, 226, 0.35);

  /* Typography */
  --font-family:      'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-size-xs:     0.75rem;    /* 12px */
  --font-size-sm:     0.875rem;   /* 14px */
  --font-size-base:   1rem;       /* 16px */
  --font-size-md:     1.125rem;   /* 18px */
  --font-size-lg:     1.25rem;    /* 20px */
  --font-size-xl:     1.5rem;     /* 24px */
  --font-size-2xl:    1.875rem;   /* 30px */
  --font-size-3xl:    2.25rem;    /* 36px */
  --font-size-4xl:    3rem;       /* 48px */

  /* Spacing */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;

  /* Transitions */
  --transition-fast:   150ms ease;
  --transition-base:   250ms ease;
  --transition-slow:   350ms ease;

  /* Layout */
  --container-max:   1100px;
  --container-pad:   1.25rem;
}

/* =====================================================
   3. BASE BODY & TYPOGRAPHY
   ===================================================== */
body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  color: var(--text-dark);
  background: linear-gradient(160deg, var(--bg-light) 0%, var(--bg-lighter) 100%);
  background-attachment: fixed;
}

/* =====================================================
   4. LAYOUT UTILITIES
   ===================================================== */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-pad);
}

.hidden {
  display: none !important;
}

/* =====================================================
   5. NAVBAR
   ===================================================== */
.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--card-border);
  box-shadow: var(--shadow-sm);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: var(--space-6);
}

.navbar__logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.01em;
  flex-shrink: 0;
  transition: color var(--transition-fast);
}

.navbar__logo:hover {
  color: var(--primary);
}

.navbar__logo-icon {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
}

.navbar__links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.navbar__link {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--text-medium);
  border-radius: var(--border-radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.navbar__link:hover,
.navbar__link--active {
  color: var(--primary);
  background: var(--primary-alpha);
}

/* Hamburger toggle (mobile) */
.navbar__toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius-sm);
  transition: background var(--transition-fast);
}

.navbar__toggle:hover {
  background: var(--bg-light);
}

.navbar__toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-dark);
  border-radius: var(--border-radius-pill);
  transition: transform var(--transition-base), opacity var(--transition-fast);
}

/* =====================================================
   6. HERO SECTION
   ===================================================== */
.hero {
  background: linear-gradient(135deg, #EBF4FF 0%, #F0F4F8 50%, #F4F0FF 100%);
  padding: var(--space-20) 0 var(--space-16);
  text-align: center;
  overflow: hidden;
  position: relative;
}

.hero::before {
  content: '';
  position: absolute;
  top: -40%;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, rgba(74,144,226,0.07) 0%, transparent 70%);
  pointer-events: none;
}

.hero__inner {
  position: relative;
  z-index: 1;
}

.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  background: var(--primary-alpha);
  color: var(--primary);
  border: 1px solid rgba(74, 144, 226, 0.2);
  border-radius: var(--border-radius-pill);
  padding: var(--space-1) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 600;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  margin-bottom: var(--space-5);
}

.hero__title {
  font-size: clamp(var(--font-size-2xl), 5vw, var(--font-size-4xl));
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-5);
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

.hero__subtitle {
  font-size: var(--font-size-md);
  color: var(--text-muted);
  max-width: 520px;
  margin: 0 auto var(--space-10);
  line-height: 1.7;
}

.hero__stats {
  display: inline-flex;
  align-items: center;
  gap: var(--space-6);
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius-xl);
  padding: var(--space-3) var(--space-8);
  box-shadow: var(--shadow-sm);
  flex-wrap: wrap;
  justify-content: center;
}

.hero__stat {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
}

.hero__stat strong {
  color: var(--primary);
  font-weight: 700;
  margin-right: 3px;
}

.hero__stat-divider {
  width: 1px;
  height: 20px;
  background: var(--card-border);
}

/* =====================================================
   7. AD CONTAINERS
   ===================================================== */
.ad-container {
  text-align: center;
  padding: var(--space-4) var(--container-pad);
  background: var(--bg-white);
  border-top: 1px solid var(--card-border);
  border-bottom: 1px solid var(--card-border);
}

.ad-label {
  font-size: 10px;
  font-weight: 500;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-2);
}

.ad-placeholder {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 90px;
  min-width: min(728px, 100%);
  max-width: 100%;
  background: linear-gradient(135deg, var(--bg-light), var(--bg-lighter));
  border: 2px dashed var(--card-border);
  border-radius: var(--border-radius);
  color: var(--text-light);
  font-size: var(--font-size-sm);
  font-weight: 500;
}

.ad-container--hero {
  padding: var(--space-5) var(--container-pad);
}

/* =====================================================
   8. SECTION TITLES
   ===================================================== */
.section-title {
  font-size: clamp(var(--font-size-xl), 3vw, var(--font-size-2xl));
  font-weight: 700;
  color: var(--text-dark);
  text-align: center;
  letter-spacing: -0.015em;
  margin-bottom: var(--space-2);
}

.section-subtitle {
  font-size: var(--font-size-base);
  color: var(--text-muted);
  text-align: center;
  margin-bottom: var(--space-10);
}

/* =====================================================
   9. CALCULATOR SECTION
   ===================================================== */
.calculator-section {
  padding: var(--space-16) 0;
}

.calculator-card {
  background: var(--card-bg);
  border-radius: var(--border-radius-lg);
  border: 1px solid var(--card-border);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  max-width: 600px;
  margin: 0 auto;
}

/* =====================================================
   10. TABS
   ===================================================== */
.tabs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  background: var(--bg-light);
  border-bottom: 1px solid var(--card-border);
}

.tab-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-muted);
  background: transparent;
  border-bottom: 3px solid transparent;
  transition: color var(--transition-base), background var(--transition-base), border-color var(--transition-base);
  cursor: pointer;
  white-space: nowrap;
}

.tab-btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.tab-btn:hover {
  color: var(--primary);
  background: rgba(74, 144, 226, 0.04);
}

.tab-btn--active {
  color: var(--primary);
  background: var(--card-bg);
  border-bottom-color: var(--primary);
}

/* =====================================================
   11. TAB PANELS
   ===================================================== */
.tab-panel {
  padding: var(--space-8);
}

/* =====================================================
   12. CALC FORM & FORM GROUPS
   ===================================================== */
.calc-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.form-group--toggle {
  flex-direction: row;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.form-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-medium);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.form-label--optional {
  font-weight: 400;
  color: var(--text-muted);
  font-size: var(--font-size-xs);
}

/* =====================================================
   13. UNIT TOGGLE (PILL)
   ===================================================== */
.unit-toggle,
.gender-toggle {
  display: flex;
  background: var(--bg-light);
  border-radius: var(--border-radius-pill);
  padding: 3px;
  gap: 2px;
  border: 1px solid var(--card-border);
}

.unit-toggle input[type="radio"],
.gender-toggle input[type="radio"] {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
  pointer-events: none;
}

.unit-toggle__btn,
.gender-toggle__btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: var(--space-2) var(--space-5);
  border-radius: var(--border-radius-pill);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  transition: background var(--transition-fast), color var(--transition-fast), box-shadow var(--transition-fast);
  user-select: none;
  white-space: nowrap;
}

.gender-toggle__btn svg {
  width: 14px;
  height: 14px;
}

.unit-toggle input[type="radio"]:checked + .unit-toggle__btn,
.gender-toggle input[type="radio"]:checked + .gender-toggle__btn {
  background: var(--card-bg);
  color: var(--primary);
  box-shadow: var(--shadow-sm);
}

.unit-toggle input[type="radio"]:focus-visible + .unit-toggle__btn,
.gender-toggle input[type="radio"]:focus-visible + .gender-toggle__btn {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.unit-toggle__btn:hover,
.gender-toggle__btn:hover {
  color: var(--primary);
}

/* =====================================================
   14. INPUTS
   ===================================================== */
.input-with-unit {
  display: flex;
  align-items: stretch;
  border: 1.5px solid var(--card-border);
  border-radius: var(--border-radius);
  background: var(--card-bg);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  overflow: hidden;
}

.input-with-unit:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-alpha);
}

.form-input {
  flex: 1;
  min-width: 0;
  min-height: 44px;
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-base);
  font-weight: 500;
  color: var(--text-dark);
  background: transparent;
  border: none;
  outline: none;
}

.form-input::placeholder {
  color: var(--text-light);
  font-weight: 400;
}

/* Remove number input arrows */
.form-input::-webkit-outer-spin-button,
.form-input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.form-input[type="number"] {
  -moz-appearance: textfield;
}

.input-unit {
  display: flex;
  align-items: center;
  padding: 0 var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-light);
  border-left: 1.5px solid var(--card-border);
  white-space: nowrap;
}

.input-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-3);
}

/* Select */
.form-select {
  width: 100%;
  min-height: 44px;
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-base);
  font-weight: 500;
  color: var(--text-dark);
  background: var(--card-bg);
  border: 1.5px solid var(--card-border);
  border-radius: var(--border-radius);
  outline: none;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23718096' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round' fill='none'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 36px;
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-alpha);
}

/* Textarea */
.form-textarea {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-base);
  color: var(--text-dark);
  background: var(--card-bg);
  border: 1.5px solid var(--card-border);
  border-radius: var(--border-radius);
  outline: none;
  resize: vertical;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  line-height: 1.6;
}

.form-textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-alpha);
}

.form-textarea::placeholder {
  color: var(--text-light);
}

.char-counter {
  display: block;
  text-align: right;
  font-size: var(--font-size-xs);
  color: var(--text-muted);
  margin-top: var(--space-1);
}

/* Form Error */
.form-error {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-4);
  background: var(--danger-light);
  border: 1px solid rgba(255, 77, 79, 0.2);
  border-radius: var(--border-radius-sm);
  font-size: var(--font-size-sm);
  color: var(--danger);
  font-weight: 500;
}

/* Help button */
.help-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--text-light);
  color: var(--bg-white);
  font-size: 10px;
  font-weight: 700;
  cursor: help;
  transition: background var(--transition-fast);
  flex-shrink: 0;
}

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

/* =====================================================
   15. BUTTONS
   ===================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: 44px;
  padding: var(--space-3) var(--space-6);
  border-radius: var(--border-radius);
  font-size: var(--font-size-base);
  font-weight: 600;
  letter-spacing: 0.01em;
  white-space: nowrap;
  cursor: pointer;
  transition: background var(--transition-fast), color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast), border-color var(--transition-fast);
  user-select: none;
  border: 2px solid transparent;
}

.btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.btn:active {
  transform: translateY(1px);
}

.btn:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 2px;
}

/* Primary */
.btn--primary {
  background: var(--primary);
  color: var(--text-white);
  border-color: var(--primary);
  box-shadow: var(--shadow-primary);
}

.btn--primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  box-shadow: 0 6px 20px rgba(74, 144, 226, 0.45);
}

/* Outline */
.btn--outline {
  background: transparent;
  color: var(--text-medium);
  border-color: var(--card-border);
}

.btn--outline:hover {
  background: var(--bg-light);
  border-color: var(--text-light);
  color: var(--text-dark);
}

.btn--full {
  width: 100%;
}

.btn--print {
  margin-top: var(--space-4);
  font-size: var(--font-size-sm);
  padding: var(--space-2) var(--space-5);
  min-height: 40px;
}

.form-actions {
  display: flex;
  gap: var(--space-3);
  margin-top: var(--space-2);
}

.form-actions .btn {
  flex: 1;
}

/* =====================================================
   16. RESULTS SECTION
   ===================================================== */
.results-section {
  padding: var(--space-16) 0;
  background: linear-gradient(180deg, var(--bg-lighter) 0%, var(--bg-light) 100%);
}

.results-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
}

/* =====================================================
   17. RESULT CARDS
   ===================================================== */
.result-card {
  background: var(--card-bg);
  border-radius: var(--border-radius-lg);
  border: 1px solid var(--card-border);
  box-shadow: var(--shadow);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-4);
  transition: box-shadow var(--transition-base);
}

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

.result-card__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.result-card__title {
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--text-dark);
}

.result-card__abbr {
  font-size: var(--font-size-xs);
  font-weight: 700;
  color: var(--primary);
  background: var(--primary-alpha);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--border-radius-pill);
  letter-spacing: 0.05em;
}

/* Gauge Container */
.gauge-container {
  width: 100%;
  max-width: 200px;
  aspect-ratio: 200/120;
  position: relative;
}

.gauge-container canvas {
  width: 100%;
  height: auto;
}

/* Metric Value */
.result-card__metric {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}

.result-card__number {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.03em;
  line-height: 1;
  transition: color var(--transition-base);
}

.result-card__unit {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--text-muted);
}

/* Category Badge */
.result-card__category {
  width: 100%;
}

.category-badge {
  display: inline-block;
  padding: var(--space-2) var(--space-5);
  border-radius: var(--border-radius-pill);
  font-size: var(--font-size-sm);
  font-weight: 600;
  background: var(--bg-light);
  color: var(--text-muted);
  transition: background var(--transition-base), color var(--transition-base);
}

.category-badge--underweight {
  background: var(--info-light);
  color: var(--info);
}

.category-badge--normal,
.category-badge--fitness,
.category-badge--athlete {
  background: var(--success-light);
  color: var(--success);
}

.category-badge--overweight,
.category-badge--average {
  background: var(--warning-light);
  color: var(--warning);
}

.category-badge--obese,
.category-badge--essential {
  background: var(--danger-light);
  color: var(--danger);
}

/* Insight */
.result-card__insight {
  width: 100%;
  padding: var(--space-4);
  background: var(--bg-light);
  border-radius: var(--border-radius);
  font-size: var(--font-size-sm);
  color: var(--text-medium);
  line-height: 1.65;
  text-align: left;
}

/* Range List */
.result-card__ranges {
  width: 100%;
  text-align: left;
}

.result-card__ranges-title {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: var(--space-3);
}

.range-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.range-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--font-size-sm);
  color: var(--text-medium);
}

.range-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.range-item--info    .range-dot { background: var(--info); }
.range-item--success .range-dot { background: var(--success); }
.range-item--warning .range-dot { background: var(--warning); }
.range-item--danger  .range-dot { background: var(--danger); }

/* Disclaimer */
.disclaimer {
  display: flex;
  gap: var(--space-3);
  align-items: flex-start;
  padding: var(--space-5);
  background: var(--warning-light);
  border: 1px solid rgba(250, 173, 20, 0.25);
  border-radius: var(--border-radius);
  max-width: 800px;
  margin: 0 auto;
}

.disclaimer svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  color: var(--warning);
  margin-top: 2px;
}

.disclaimer p {
  font-size: var(--font-size-sm);
  color: var(--text-medium);
  line-height: 1.6;
}

/* =====================================================
   18. EDUCATIONAL CONTENT
   ===================================================== */
.educational-wrapper {
  padding: var(--space-16) 0;
  background: var(--bg-white);
}

.educational-inner {
  display: flex;
  flex-direction: column;
  gap: var(--space-16);
}

.edu-section {
  max-width: 780px;
  margin: 0 auto;
  width: 100%;
}

.edu-section__icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-4);
  display: block;
  line-height: 1;
}

.edu-section__title {
  font-size: clamp(var(--font-size-xl), 3vw, var(--font-size-2xl));
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.015em;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 2px solid var(--bg-light);
}

.edu-section__subtitle {
  font-size: var(--font-size-md);
  font-weight: 600;
  color: var(--text-dark);
  margin: var(--space-6) 0 var(--space-3);
}

.edu-section__body {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.edu-section__body p {
  font-size: var(--font-size-base);
  color: var(--text-medium);
  line-height: 1.75;
}

.edu-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  padding-left: var(--space-2);
}

.edu-list li {
  font-size: var(--font-size-base);
  color: var(--text-medium);
  line-height: 1.65;
  padding-left: var(--space-5);
  position: relative;
}

.edu-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 10px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--primary);
}

.formula-box {
  background: var(--bg-light);
  border-left: 3px solid var(--primary);
  border-radius: 0 var(--border-radius) var(--border-radius) 0;
  padding: var(--space-5) var(--space-6);
  font-size: var(--font-size-sm);
  color: var(--text-dark);
  font-family: 'Courier New', Courier, monospace;
  line-height: 1.9;
}

/* Comparison Table */
.comparison-table-wrapper {
  width: 100%;
  overflow-x: auto;
  border-radius: var(--border-radius);
  border: 1px solid var(--card-border);
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--font-size-sm);
}

.comparison-table th {
  background: var(--bg-light);
  color: var(--text-medium);
  font-weight: 700;
  padding: var(--space-3) var(--space-4);
  text-align: left;
  border-bottom: 1px solid var(--card-border);
}

.comparison-table td {
  padding: var(--space-3) var(--space-4);
  color: var(--text-medium);
  border-bottom: 1px solid var(--bg-light);
}

.comparison-table tr:last-child td {
  border-bottom: none;
}

.comparison-table tr:nth-child(even) td {
  background: rgba(240, 244, 248, 0.5);
}

.cell-yes {
  color: var(--success);
  font-weight: 600;
}

.cell-no {
  color: var(--danger);
  font-weight: 600;
}

/* =====================================================
   19. FAQ SECTION
   ===================================================== */
.faq-section {
  padding: var(--space-16) 0;
  background: linear-gradient(180deg, var(--bg-light) 0%, var(--bg-lighter) 100%);
}

.faq-list {
  max-width: 780px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.faq-item {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: box-shadow var(--transition-base);
}

.faq-item[open] {
  box-shadow: var(--shadow);
}

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

.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-5) var(--space-6);
  font-size: var(--font-size-base);
  font-weight: 600;
  color: var(--text-dark);
  cursor: pointer;
  list-style: none;
  user-select: none;
  transition: background var(--transition-fast), color var(--transition-fast);
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::marker {
  display: none;
}

.faq-question:hover {
  background: var(--bg-light);
  color: var(--primary);
}

.faq-chevron {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  color: var(--text-muted);
  transition: transform var(--transition-base);
}

.faq-answer {
  padding: 0 var(--space-6) var(--space-5);
  font-size: var(--font-size-base);
  color: var(--text-medium);
  line-height: 1.75;
  border-top: 1px solid var(--bg-light);
  animation: fadeInDown 200ms ease;
}

.faq-answer p,
.faq-answer ul {
  margin-top: var(--space-3);
}

.faq-answer ul {
  list-style: disc;
  padding-left: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* =====================================================
   20. FOOTER
   ===================================================== */
.footer {
  background: var(--bg-dark);
  color: rgba(255,255,255,0.85);
  padding: var(--space-16) 0 0;
}

.footer__inner {
  display: flex;
  flex-direction: column;
  gap: var(--space-12);
}

.footer__grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1.4fr;
  gap: var(--space-10);
}

.footer__logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--text-white);
  margin-bottom: var(--space-4);
}

.footer__logo-icon {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
}

.footer__tagline {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.6);
  line-height: 1.65;
  margin-bottom: var(--space-4);
}

.footer__contact {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
}

.footer__contact svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
  color: rgba(255,255,255,0.5);
}

.footer__email {
  font-size: var(--font-size-sm);
  color: var(--primary);
  transition: color var(--transition-fast);
}

.footer__email:hover {
  color: #7ab8f5;
}

.footer__built-by {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.5);
}

.footer__built-by strong {
  color: rgba(255,255,255,0.8);
}

.footer__col-title {
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: rgba(255,255,255,0.5);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-5);
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer__link {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.65);
  transition: color var(--transition-fast);
}

.footer__link:hover {
  color: var(--text-white);
}

/* Share Buttons */
.share-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.share-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--border-radius-pill);
  font-size: var(--font-size-sm);
  font-weight: 600;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
  color: var(--text-white);
}

.share-btn svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.share-btn:hover {
  opacity: 0.88;
  transform: translateY(-1px);
}

.share-btn:active {
  transform: translateY(0);
}

.share-btn--twitter   { background: #1DA1F2; }
.share-btn--facebook  { background: #1877F2; }
.share-btn--whatsapp  { background: #25D366; }

/* Footer Bottom */
.footer__bottom {
  border-top: 1px solid rgba(255,255,255,0.08);
  padding: var(--space-6) 0;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.visitor-counter {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-xs);
  color: rgba(255,255,255,0.4);
}

.visitor-counter svg {
  width: 14px;
  height: 14px;
}

.footer__copyright {
  font-size: var(--font-size-xs);
  color: rgba(255,255,255,0.4);
  text-align: center;
}

.footer__disclaimer-short {
  font-size: var(--font-size-xs);
  color: rgba(255,255,255,0.3);
  text-align: right;
}

/* =====================================================
   21. FEEDBACK FAB
   ===================================================== */
.feedback-fab {
  position: fixed;
  bottom: 28px;
  right: 24px;
  z-index: 900;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  background: var(--primary);
  color: var(--text-white);
  border-radius: var(--border-radius-pill);
  box-shadow: var(--shadow-lg), var(--shadow-primary);
  font-size: var(--font-size-sm);
  font-weight: 600;
  transition: background var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
}

.feedback-fab svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.feedback-fab:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg), 0 6px 20px rgba(74, 144, 226, 0.5);
}

.feedback-fab:active {
  transform: translateY(0);
}

.feedback-fab__label {
  white-space: nowrap;
}

/* =====================================================
   22. FEEDBACK MODAL
   ===================================================== */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 1100;
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-5);
  animation: overlayIn 200ms ease;
}

.modal-overlay[hidden] {
  display: none !important;
}

@keyframes overlayIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

.modal-card {
  background: var(--card-bg);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 460px;
  animation: modalIn 250ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes modalIn {
  from {
    opacity: 0;
    transform: scale(0.9) translateY(12px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-6) var(--space-6) var(--space-4);
  border-bottom: 1px solid var(--card-border);
}

.modal-title {
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--text-dark);
}

.modal-close {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius-sm);
  color: var(--text-muted);
  transition: background var(--transition-fast), color var(--transition-fast);
}

.modal-close svg {
  width: 18px;
  height: 18px;
}

.modal-close:hover {
  background: var(--bg-light);
  color: var(--text-dark);
}

.modal-form {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.modal-actions {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-top: var(--space-2);
}

/* =====================================================
   23. TOAST NOTIFICATION
   ===================================================== */
.toast {
  position: fixed;
  bottom: 28px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1200;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-6);
  background: var(--text-dark);
  color: var(--text-white);
  border-radius: var(--border-radius-pill);
  box-shadow: var(--shadow-lg);
  font-size: var(--font-size-sm);
  font-weight: 500;
  animation: toastIn 300ms cubic-bezier(0.34, 1.56, 0.64, 1);
  white-space: nowrap;
  max-width: calc(100vw - 2rem);
}

.toast[hidden] {
  display: none !important;
}

.toast svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

@keyframes toastIn {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
  }
}

/* =====================================================
   24. SUB-PAGE STYLES (about, privacy, terms, contact, howto)
   ===================================================== */

/* Sub-page navbar (maps .nav-* classes to match main navbar) */
.nav-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-pad);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: var(--space-6);
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.01em;
  flex-shrink: 0;
  transition: color var(--transition-fast);
}

.nav-brand:hover {
  color: var(--primary);
}

.nav-brand-icon {
  color: var(--primary);
  font-size: 1.2em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav-links a {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--text-medium);
  border-radius: var(--border-radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--primary);
  background: var(--primary-alpha);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius-sm);
  transition: background var(--transition-fast);
}

.nav-toggle:hover {
  background: var(--bg-light);
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-dark);
  border-radius: var(--border-radius-pill);
}

/* Page content area */
.page-content {
  padding: var(--space-12) 0 var(--space-16);
  min-height: 60vh;
}

/* Prose card for article content */
.prose-card {
  background: var(--card-bg);
  border-radius: var(--border-radius-lg);
  border: 1px solid var(--card-border);
  box-shadow: var(--shadow);
  padding: var(--space-10) var(--space-8);
  max-width: 800px;
  margin: 0 auto;
}

.prose-card h1 {
  font-size: clamp(var(--font-size-2xl), 4vw, var(--font-size-3xl));
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 2px solid var(--bg-light);
}

.prose-card h2 {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--text-dark);
  margin-top: var(--space-10);
  margin-bottom: var(--space-4);
}

.prose-card h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--text-dark);
  margin-top: var(--space-6);
  margin-bottom: var(--space-3);
}

.prose-card h4 {
  font-size: var(--font-size-md);
  font-weight: 600;
  color: var(--text-dark);
  margin-top: var(--space-5);
  margin-bottom: var(--space-2);
}

.prose-card p {
  font-size: var(--font-size-base);
  color: var(--text-medium);
  line-height: 1.75;
  margin-bottom: var(--space-4);
}

.prose-card ul,
.prose-card ol {
  padding-left: var(--space-6);
  margin-bottom: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.prose-card ul {
  list-style: disc;
}

.prose-card ol {
  list-style: decimal;
}

.prose-card li {
  font-size: var(--font-size-base);
  color: var(--text-medium);
  line-height: 1.65;
}

.prose-card a {
  color: var(--primary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.prose-card a:hover {
  color: var(--primary-dark);
}

.prose-card details {
  background: var(--bg-light);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius);
  margin-bottom: var(--space-3);
  overflow: hidden;
}

.prose-card summary {
  padding: var(--space-4) var(--space-5);
  font-weight: 600;
  color: var(--text-dark);
  cursor: pointer;
  transition: background var(--transition-fast);
}

.prose-card summary:hover {
  background: var(--bg-lighter);
}

.prose-card details p {
  padding: 0 var(--space-5) var(--space-4);
}

.prose-card details ul {
  padding: 0 var(--space-5) var(--space-4) var(--space-10);
}

.prose-card .last-updated {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  margin-bottom: var(--space-6);
}

/* Contact page layout */
.contact-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-8);
  max-width: 900px;
  margin: 0 auto;
}

.contact-form-card {
  max-width: none;
}

/* Sub-page simple footer */
.site-footer {
  background: var(--bg-dark);
  color: rgba(255,255,255,0.85);
  padding: var(--space-8) 0;
}

.site-footer .footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.site-footer .footer-copy {
  font-size: var(--font-size-xs);
  color: rgba(255,255,255,0.5);
}

.site-footer .footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
}

.site-footer .footer-links a {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.6);
  transition: color var(--transition-fast);
}

.site-footer .footer-links a:hover {
  color: var(--text-white);
}

.site-footer .footer-brand {
  font-size: var(--font-size-xs);
  color: rgba(255,255,255,0.4);
}

.site-footer .footer-brand strong {
  color: rgba(255,255,255,0.7);
}

/* =====================================================
   25. PRINT STYLES
   ===================================================== */
@media print {
  .navbar,
  .hero,
  .calculator-section,
  .ad-container,
  .educational-wrapper,
  .faq-section,
  .feedback-fab,
  .modal-overlay,
  .toast,
  .footer__bottom .visitor-counter,
  .share-buttons,
  .btn--print {
    display: none !important;
  }

  .results-section {
    padding: 0;
    background: white;
  }

  .result-card {
    border: 1px solid #ccc;
    box-shadow: none;
    break-inside: avoid;
  }

  .footer {
    background: white;
    color: black;
    padding: 16px;
  }

  .footer__link,
  .footer__email {
    color: black;
  }
}

/* =====================================================
   25. RESPONSIVE — MOBILE FIRST
   ===================================================== */

/* ---- 768px and below ---- */
@media (max-width: 768px) {
  :root {
    --container-pad: 1rem;
  }

  /* Navbar */
  .navbar__toggle {
    display: flex;
  }

  .navbar__links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--card-bg);
    border-bottom: 1px solid var(--card-border);
    box-shadow: var(--shadow-md);
    padding: var(--space-3) var(--space-4);
    z-index: 999;
  }

  .navbar__links.is-open {
    display: flex;
  }

  .navbar__link {
    padding: var(--space-3) var(--space-4);
    border-radius: var(--border-radius-sm);
    font-size: var(--font-size-base);
  }

  /* Hero */
  .hero {
    padding: var(--space-12) 0 var(--space-10);
  }

  .hero__stats {
    gap: var(--space-4);
    padding: var(--space-3) var(--space-5);
  }

  .hero__stat-divider {
    display: none;
  }

  /* Calculator */
  .calculator-section {
    padding: var(--space-10) 0;
  }

  .tab-panel {
    padding: var(--space-5);
  }

  .tab-btn {
    font-size: var(--font-size-xs);
    padding: var(--space-3) var(--space-3);
    gap: var(--space-1);
  }

  .tab-btn svg {
    width: 16px;
    height: 16px;
  }

  .form-group--toggle {
    flex-direction: column;
    align-items: flex-start;
  }

  /* Results */
  .results-grid {
    grid-template-columns: 1fr;
  }

  .results-section {
    padding: var(--space-10) 0;
  }

  /* Footer */
  .footer__grid {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }

  .footer__bottom {
    flex-direction: column;
    text-align: center;
    gap: var(--space-3);
  }

  .footer__disclaimer-short {
    text-align: center;
  }

  /* Educational */
  .educational-wrapper {
    padding: var(--space-10) 0;
  }

  .educational-inner {
    gap: var(--space-10);
  }

  .edu-section__title {
    font-size: var(--font-size-xl);
  }

  /* FAQ */
  .faq-section {
    padding: var(--space-10) 0;
  }

  .faq-question {
    padding: var(--space-4) var(--space-5);
    font-size: var(--font-size-sm);
  }

  .faq-answer {
    padding: 0 var(--space-5) var(--space-4);
  }

  /* Sub-page nav */
  .nav-toggle {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--card-bg);
    border-bottom: 1px solid var(--card-border);
    box-shadow: var(--shadow-md);
    padding: var(--space-3) var(--space-4);
    z-index: 999;
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    padding: var(--space-3) var(--space-4);
    border-radius: var(--border-radius-sm);
    font-size: var(--font-size-base);
  }

  /* Sub-page content */
  .page-content {
    padding: var(--space-8) 0 var(--space-10);
  }

  .prose-card {
    padding: var(--space-6) var(--space-5);
  }

  .contact-layout {
    grid-template-columns: 1fr;
  }

  .site-footer .footer-inner {
    flex-direction: column;
    text-align: center;
  }

  /* Feedback FAB */
  .feedback-fab__label {
    display: none;
  }

  .feedback-fab {
    width: 52px;
    height: 52px;
    border-radius: 50%;
    padding: 0;
    justify-content: center;
  }
}

/* ---- 480px and below ---- */
@media (max-width: 480px) {
  .hero__title {
    font-size: var(--font-size-2xl);
  }

  .input-split {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-2);
  }

  .form-actions {
    flex-direction: column;
  }

  .result-card__number {
    font-size: var(--font-size-2xl);
  }

  .share-buttons {
    flex-direction: column;
  }

  .share-btn {
    justify-content: center;
  }
}

/* ---- 1024px and above ---- */
@media (min-width: 1024px) {
  .calculator-card {
    max-width: 620px;
  }

  .tab-panel {
    padding: var(--space-10);
  }

  .footer__grid {
    gap: var(--space-12);
  }
}