/* ===== CSS VARIABLES ===== */
:root {
  --blue-50: #eff6ff;
  --blue-100: #dbeafe;
  --blue-200: #bfdbfe;
  --blue-400: #60a5fa;
  --blue-500: #3b82f6;
  --blue-600: #2563eb;
  --blue-700: #1d4ed8;
  --blue-800: #1e40af;
  --blue-900: #1e3a5f;

  --green-50: #ecfdf5;
  --green-100: #d1fae5;
  --green-400: #34d399;
  --green-500: #10b981;
  --green-600: #059669;
  --green-700: #047857;
  --green-800: #065f46;

  --gray-50: #f8fafc;
  --gray-100: #f1f5f9;
  --gray-200: #e2e8f0;
  --gray-300: #cbd5e1;
  --gray-400: #94a3b8;
  --gray-500: #64748b;
  --gray-600: #475569;
  --gray-700: #334155;
  --gray-800: #1e293b;
  --gray-900: #0f172a;

  --white: #ffffff;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 8px 10px -6px rgba(0,0,0,0.1);
  --radius: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 100%;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 18px;
  line-height: 1.7;
  color: var(--gray-800);
  background: var(--gray-50);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img { max-width: 100%; display: block; }
a { color: var(--blue-600); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--blue-700); }
ul { list-style: none; }

/* ===== CONTAINER ===== */
.container {
  width: 100%;
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== HERO SECTION ===== */
.hero {
  position: relative;
  min-height: 85vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 120px 0 80px;
  overflow: hidden;
  background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-800) 40%, #1a365d 100%);
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(59,130,246,0.15) 0%, transparent 60%),
    radial-gradient(ellipse at 80% 20%, rgba(16,185,129,0.1) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 80%, rgba(59,130,246,0.08) 0%, transparent 50%);
  pointer-events: none;
}

.hero__inner {
  position: relative;
  z-index: 1;
  max-width: 800px;
}

.hero__badge {
  display: inline-block;
  padding: 8px 20px;
  background: rgba(255,255,255,0.1);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255,255,255,0.15);
  border-radius: 50px;
  color: var(--blue-200);
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  margin-bottom: 28px;
  animation: fadeInDown 0.8s ease;
}

.hero__title {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  color: var(--white);
  line-height: 1.15;
  margin-bottom: 20px;
  letter-spacing: -0.02em;
  animation: fadeInUp 0.8s ease 0.1s both;
}

.hero__subtitle {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  color: rgba(255,255,255,0.8);
  font-weight: 400;
  max-width: 600px;
  margin: 0 auto 36px;
  line-height: 1.6;
  animation: fadeInUp 0.8s ease 0.2s both;
}

.hero__stats {
  display: flex;
  justify-content: center;
  gap: 48px;
  margin-top: 48px;
  animation: fadeInUp 0.8s ease 0.4s both;
}

.hero__stat {
  text-align: center;
}

.hero__stat-number {
  display: block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--green-400);
  margin-bottom: 4px;
}

.hero__stat-label {
  font-size: 0.875rem;
  color: rgba(255,255,255,0.6);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 16px 32px;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  position: relative;
  white-space: nowrap;
}

.btn--primary {
  background: linear-gradient(135deg, var(--blue-500) 0%, var(--blue-700) 100%);
  color: var(--white);
  box-shadow: 0 4px 14px rgba(37,99,235,0.35);
}

.btn--primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(37,99,235,0.45);
  color: var(--white);
}

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

.btn--large {
  padding: 18px 40px;
  font-size: 1.125rem;
  border-radius: var(--radius-lg);
}

.btn--full {
  width: 100%;
  padding: 18px;
  font-size: 1.125rem;
}

.btn__spinner {
  display: none;
}

.btn--loading .btn__text { visibility: hidden; }
.btn--loading .btn__spinner {
  display: flex;
  position: absolute;
}

/* ===== NAVIGATION ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--gray-200);
  transition: all var(--transition);
}

.nav--scrolled {
  background: rgba(255,255,255,0.97);
  box-shadow: var(--shadow-md);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.nav__logo {
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--gray-900);
  text-decoration: none;
}

.nav__logo-accent {
  color: var(--blue-500);
}

.nav__links {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav__links a {
  padding: 8px 16px;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--gray-600);
  border-radius: 8px;
  transition: all var(--transition);
}

.nav__links a:hover {
  color: var(--blue-600);
  background: var(--blue-50);
}

.nav__toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav__toggle span {
  display: block;
  width: 24px;
  height: 2.5px;
  background: var(--gray-700);
  border-radius: 2px;
  transition: all var(--transition);
}

.nav__toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.nav__toggle.active span:nth-child(2) { opacity: 0; }
.nav__toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ===== SECTIONS ===== */
.section {
  padding: 80px 0;
}

.section--light {
  background: var(--gray-50);
}

.section--white {
  background: var(--white);
}

.section--dark {
  background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-800) 100%);
  padding: 80px 0 100px;
}

.section__header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto 48px;
}

.section__title {
  font-size: clamp(1.6rem, 3.5vw, 2.25rem);
  font-weight: 700;
  color: var(--gray-900);
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.section__title--light {
  color: var(--white);
}

.section__desc {
  font-size: 1.1rem;
  color: var(--gray-500);
  line-height: 1.6;
}

.section__desc--light {
  color: rgba(255,255,255,0.7);
}

/* ===== CALCULATOR CARD ===== */
.calculator-card {
  max-width: 780px;
  margin: 0 auto;
  background: var(--white);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  padding: 48px;
}

.calculator-form {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

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

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-label {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--gray-700);
}

.form-input-wrap {
  position: relative;
  display: flex;
  align-items: center;
}

.form-input {
  width: 100%;
  padding: 14px 16px;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--gray-800);
  background: var(--gray-50);
  border: 2px solid var(--gray-200);
  border-radius: var(--radius);
  transition: all var(--transition);
  outline: none;
}

.form-input:focus {
  border-color: var(--blue-400);
  background: var(--white);
  box-shadow: 0 0 0 4px rgba(59,130,246,0.1);
}

.form-input::placeholder {
  color: var(--gray-400);
}

.form-input-wrap--prepend .form-input {
  padding-left: 40px;
}

.form-input-wrap--append .form-input {
  padding-right: 40px;
}

.input-prepend,
.input-append {
  position: absolute;
  font-size: 1rem;
  font-weight: 600;
  color: var(--gray-500);
  pointer-events: none;
}

.input-prepend {
  left: 14px;
}

.input-append {
  right: 14px;
}

.form-help {
  font-size: 0.8rem;
  color: var(--gray-400);
  margin-top: 2px;
}

.form-input--error {
  border-color: #ef4444;
  background: #fef2f2;
}

.form-error {
  font-size: 0.8rem;
  color: #ef4444;
  font-weight: 500;
}

/* ===== RESULTS ===== */
.results-summary {
  text-align: center;
  margin-bottom: 40px;
}

.results-summary__text {
  font-size: 1.15rem;
  color: rgba(255,255,255,0.75);
  font-weight: 400;
}

.results-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
  opacity: 0;
  transform: translateY(20px);
  transition: all 0.6s ease;
}

.results-grid--visible {
  opacity: 1;
  transform: translateY(0);
}

.result-card {
  background: rgba(255,255,255,0.08);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  text-align: center;
  transition: all var(--transition);
}

.result-card:hover {
  background: rgba(255,255,255,0.12);
  transform: translateY(-4px);
}

.result-card--primary {
  background: linear-gradient(135deg, rgba(59,130,246,0.2) 0%, rgba(37,99,235,0.15) 100%);
  border-color: rgba(59,130,246,0.3);
}

.result-card--accent {
  background: linear-gradient(135deg, rgba(16,185,129,0.2) 0%, rgba(5,150,105,0.15) 100%);
  border-color: rgba(16,185,129,0.3);
}

.result-card__icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: rgba(255,255,255,0.1);
  color: var(--blue-400);
  margin-bottom: 16px;
}

.result-card--accent .result-card__icon {
  color: var(--green-400);
}

.result-card--primary .result-card__icon {
  color: var(--blue-300);
}

.result-card__label {
  font-size: 0.9rem;
  font-weight: 500;
  color: rgba(255,255,255,0.7);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.result-card__value {
  font-size: clamp(1.6rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--white);
  margin-bottom: 8px;
}

.result-card__value--green {
  color: var(--green-400);
}

.result-card__caption {
  font-size: 0.85rem;
  color: rgba(255,255,255,0.5);
}

/* ===== CHART ===== */
.chart-card {
  background: var(--white);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  padding: 32px;
  max-width: 900px;
  margin: 0 auto;
}

.chart-container {
  position: relative;
  width: 100%;
  max-height: 450px;
}

.chart-legend-custom {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--gray-200);
}

.chart-legend-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
  color: var(--gray-600);
  font-weight: 500;
}

.chart-legend-dot {
  width: 12px;
  height: 12px;
  border-radius: 4px;
}

/* ===== EDUCATIONAL CONTENT ===== */
.content-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 32px;
  max-width: 900px;
  margin: 0 auto;
}

.content-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  padding: 36px;
  transition: all var(--transition);
}

.content-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--gray-300);
}

.content-card h3 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 16px;
  letter-spacing: -0.01em;
}

.content-card p {
  font-size: 1rem;
  color: var(--gray-600);
  line-height: 1.8;
  margin-bottom: 16px;
}

.content-card p:last-child {
  margin-bottom: 0;
}

/* ===== FAQ ===== */
.faq-list {
  max-width: 780px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.faq-item {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  overflow: hidden;
  transition: all var(--transition);
}

.faq-item:hover {
  border-color: var(--gray-300);
}

.faq-item.active {
  border-color: var(--blue-200);
  box-shadow: 0 0 0 3px rgba(59,130,246,0.08);
}

.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 20px 24px;
  background: none;
  border: none;
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--gray-800);
  text-align: left;
  cursor: pointer;
  transition: all var(--transition);
}

.faq-question:hover {
  color: var(--blue-600);
}

.faq-icon {
  flex-shrink: 0;
  color: var(--gray-400);
  transition: transform var(--transition);
}

.faq-item.active .faq-icon {
  transform: rotate(180deg);
  color: var(--blue-500);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease, padding 0.4s ease;
}

.faq-item.active .faq-answer {
  max-height: 300px;
}

.faq-answer p {
  padding: 0 24px 20px;
  font-size: 0.95rem;
  color: var(--gray-600);
  line-height: 1.75;
}

/* ===== FOOTER ===== */
.footer {
  background: var(--gray-900);
  color: var(--gray-400);
  padding: 64px 0 32px;
}

.footer__inner {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer__brand .nav__logo {
  color: var(--white);
  font-size: 1.5rem;
}

.footer__tagline {
  font-size: 0.95rem;
  color: var(--gray-500);
  margin-top: 8px;
}

.footer__heading {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--white);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 16px;
}

.footer__links ul li {
  margin-bottom: 10px;
}

.footer__links a {
  font-size: 0.95rem;
  color: var(--gray-400);
}

.footer__links a:hover {
  color: var(--blue-400);
}

.footer__disclaimer {
  padding: 32px 0;
  border-top: 1px solid rgba(255,255,255,0.08);
  border-bottom: 1px solid rgba(255,255,255,0.08);
  margin-bottom: 24px;
}

.footer__disclaimer p {
  font-size: 0.8rem;
  line-height: 1.7;
  color: var(--gray-500);
}

.footer__bottom {
  text-align: center;
  font-size: 0.85rem;
  color: var(--gray-500);
}

/* ===== ANIMATIONS ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===== SCROLL ANIMATIONS ===== */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
  body { font-size: 16px; }

  .hero { min-height: auto; padding: 100px 0 60px; }
  .hero__stats { gap: 32px; }
  .hero__stat-number { font-size: 1.25rem; }

  .calculator-card { padding: 32px 24px; }

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

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

  .footer__inner {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .footer__brand { grid-column: 1 / -1; }
}

@media (max-width: 640px) {
  .nav__links {
    position: fixed;
    top: 68px;
    left: 0;
    right: 0;
    background: rgba(255,255,255,0.98);
    backdrop-filter: blur(12px);
    flex-direction: column;
    padding: 16px;
    gap: 4px;
    border-bottom: 1px solid var(--gray-200);
    transform: translateY(-100%);
    opacity: 0;
    transition: all var(--transition);
    pointer-events: none;
  }

  .nav__links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .nav__links a {
    width: 100%;
    padding: 12px 16px;
    font-size: 1.05rem;
  }

  .nav__toggle { display: flex; }

  .hero { padding: 90px 0 48px; }
  .hero__title { font-size: 1.75rem; }
  .hero__subtitle { font-size: 1rem; }
  .hero__stats { flex-direction: column; gap: 20px; }
  .hero__badge { font-size: 12px; }

  .btn--large { width: 100%; padding: 16px 24px; font-size: 1rem; }

  .section { padding: 56px 0; }
  .section__header { margin-bottom: 32px; }
  .section__desc { font-size: 1rem; }

  .calculator-card { padding: 24px 16px; border-radius: var(--radius-lg); }
  .form-input { font-size: 1rem; padding: 12px 14px; }

  .results-grid { grid-template-columns: 1fr; }
  .result-card { padding: 24px 20px; }

  .chart-card { padding: 20px; }

  .content-card { padding: 24px 20px; }
  .content-card h3 { font-size: 1.2rem; }

  .faq-question { font-size: 0.95rem; padding: 16px 20px; }
  .faq-answer p { font-size: 0.9rem; padding: 0 20px 16px; }

  .footer { padding: 48px 0 24px; }
  .footer__inner { grid-template-columns: 1fr; gap: 32px; }
}

/* ===== PRINT ===== */
@media print {
  .nav { position: static; }
  .hero { min-height: auto; padding: 40px 0; }
  .btn { display: none; }
  .section { padding: 32px 0; }
}