/* ============================================
   ТендерAI Landing Page — Styles
   Design system aligned with main platform:
   - Font: Inter
   - Colors: neutral grayscale + semantic (risk-red, risk-green, etc.)
   - Dark mode first
   ============================================ */

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

:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --bg: #0a0a0a;
  --bg-elevated: #141414;
  --bg-card: #1a1a1a;
  --bg-card-hover: #222;
  --border: rgba(255, 255, 255, 0.08);
  --border-strong: rgba(255, 255, 255, 0.15);
  --text-primary: #fafafa;
  --text-secondary: #a1a1a1;
  --text-muted: #666;
  --accent: #3b82f6;
  --accent-hover: #2563eb;
  --accent-subtle: rgba(59, 130, 246, 0.1);
  --green: #22c55e;
  --green-subtle: rgba(34, 197, 94, 0.1);
  --red: #ef4444;
  --red-subtle: rgba(239, 68, 68, 0.1);
  --yellow: #eab308;
  --yellow-subtle: rgba(234, 179, 8, 0.1);
  --radius: 0.625rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --container: 1200px;
  --container-narrow: 800px;
  --transition: 0.2s ease;
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  font-size: 16px;
  overflow-x: hidden;
}

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

ul {
  list-style: none;
}

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

/* === CONTAINER === */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}

.container--narrow {
  max-width: var(--container-narrow);
}

/* === BUTTONS === */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-weight: 500;
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  border-radius: var(--radius);
  white-space: nowrap;
  text-decoration: none;
}

.btn--primary {
  background: var(--text-primary);
  color: var(--bg);
}

.btn--primary:hover {
  background: #e5e5e5;
  transform: translateY(-1px);
}

.btn--ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-strong);
}

.btn--ghost:hover {
  color: var(--text-primary);
  border-color: var(--text-muted);
  background: var(--bg-card);
}

.btn--sm {
  padding: 8px 16px;
  font-size: 14px;
}

.btn--lg {
  padding: 14px 28px;
  font-size: 16px;
  border-radius: var(--radius-lg);
}

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

/* === HEADER === */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(10, 10, 10, 0.8);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 18px;
}

.logo__icon {
  color: var(--accent);
  font-size: 20px;
}

.nav {
  display: flex;
  gap: 32px;
}

.nav__link {
  font-size: 14px;
  color: var(--text-secondary);
  transition: color var(--transition);
}

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

.header__actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.burger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.burger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition);
}

/* === HERO === */
.hero {
  position: relative;
  padding: 160px 0 100px;
  text-align: center;
  overflow: hidden;
}

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

.hero__badge {
  display: inline-block;
  padding: 6px 16px;
  border-radius: 100px;
  border: 1px solid var(--border-strong);
  background: var(--bg-card);
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 24px;
  letter-spacing: 0.02em;
}

.hero__title {
  font-size: clamp(36px, 5.5vw, 72px);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: 20px;
  background: linear-gradient(180deg, #fff 40%, rgba(255,255,255,0.5) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero__subtitle {
  font-size: clamp(16px, 1.5vw, 20px);
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto 36px;
  line-height: 1.7;
}

.hero__actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 64px;
}

.hero__metrics {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  max-width: 900px;
  margin: 0 auto;
}

.metric {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 20px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
}

.metric__value {
  font-size: 28px;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.metric__label {
  font-size: 13px;
  color: var(--text-secondary);
}

.hero__glow {
  position: absolute;
  top: -200px;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 600px;
  background: radial-gradient(ellipse, rgba(59, 130, 246, 0.12) 0%, transparent 70%);
  pointer-events: none;
}

/* === SECTIONS === */
.section {
  padding: 100px 0;
}

.section--dark {
  background: var(--bg-elevated);
}

.section__header {
  text-align: center;
  margin-bottom: 64px;
}

.section__tag {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 100px;
  border: 1px solid var(--border-strong);
  font-size: 12px;
  font-weight: 500;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 16px;
}

.section__title {
  font-size: clamp(28px, 3.5vw, 44px);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.section__desc {
  font-size: 17px;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* === PROBLEM CARDS === */
.problems-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.problem-card {
  padding: 28px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
  transition: border-color var(--transition);
}

.problem-card:hover {
  border-color: var(--border-strong);
}

.problem-card__icon {
  font-size: 24px;
  margin-bottom: 16px;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius);
}

.problem-card__icon--red {
  background: var(--red-subtle);
  color: var(--red);
}

.problem-card__icon--yellow {
  background: var(--yellow-subtle);
  color: var(--yellow);
}

.problem-card__title {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 8px;
}

.problem-card__text {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* === FEATURES === */
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.feature-card {
  padding: 28px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
  transition: all var(--transition);
  position: relative;
}

.feature-card:hover {
  border-color: var(--border-strong);
  transform: translateY(-2px);
}

.feature-card--accent {
  border-color: var(--accent);
  background: linear-gradient(135deg, var(--accent-subtle), var(--bg-card));
  grid-column: span 2;
}

.feature-card__number {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-muted);
  margin-bottom: 16px;
  font-variant-numeric: tabular-nums;
}

.feature-card__title {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 8px;
}

.feature-card__text {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.feature-card__badge {
  position: absolute;
  top: 16px;
  right: 16px;
  padding: 4px 10px;
  border-radius: 100px;
  background: var(--accent);
  color: #fff;
  font-size: 11px;
  font-weight: 600;
}

/* === STEPS === */
.steps {
  display: flex;
  flex-direction: column;
  gap: 0;
  max-width: 700px;
  margin: 0 auto;
}

.step {
  display: flex;
  gap: 24px;
  padding: 32px 0;
  border-bottom: 1px solid var(--border);
}

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

.step__number {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  border: 1px solid var(--border-strong);
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
  background: var(--bg-card);
}

.step__title {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 6px;
}

.step__text {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 8px;
}

.step__time {
  font-size: 12px;
  font-weight: 500;
  color: var(--accent);
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--accent-subtle);
  display: inline-block;
}

/* === COMPARISON TABLE === */
.comparison-table-wrap {
  overflow-x: auto;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

.comparison-table th,
.comparison-table td {
  padding: 14px 20px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.comparison-table th {
  background: var(--bg-card);
  font-weight: 600;
  font-size: 13px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.comparison-table td {
  color: var(--text-secondary);
}

.comparison-table__highlight {
  background: var(--accent-subtle) !important;
  color: var(--text-primary) !important;
}

.comparison-table tbody tr:hover {
  background: var(--bg-card);
}

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

/* === NUMBERS === */
.numbers-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.number-card {
  text-align: center;
  padding: 32px 16px;
}

.number-card__value {
  display: block;
  font-size: clamp(24px, 3vw, 36px);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
  background: linear-gradient(135deg, var(--accent), var(--green));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.number-card__label {
  font-size: 14px;
  color: var(--text-secondary);
}

/* === PRICING === */
.pricing-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  align-items: start;
}

.pricing-card {
  padding: 32px;
  border-radius: var(--radius-xl);
  border: 1px solid var(--border);
  background: var(--bg-card);
}

.pricing-card--featured {
  border-color: var(--accent);
  background: linear-gradient(180deg, var(--accent-subtle), var(--bg-card));
  position: relative;
  transform: scale(1.03);
}

.pricing-card__badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  padding: 4px 16px;
  background: var(--accent);
  color: #fff;
  font-size: 12px;
  font-weight: 600;
  border-radius: 100px;
}

.pricing-card__header {
  margin-bottom: 24px;
}

.pricing-card__name {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 4px;
}

.pricing-card__desc {
  font-size: 14px;
  color: var(--text-secondary);
}

.pricing-card__price {
  margin-bottom: 24px;
  display: flex;
  align-items: baseline;
  gap: 4px;
}

.pricing-card__amount {
  font-size: 40px;
  font-weight: 800;
  letter-spacing: -0.03em;
}

.pricing-card__currency {
  font-size: 16px;
  color: var(--text-secondary);
  font-weight: 500;
}

.pricing-card__note {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 20px;
}

.pricing-card__features {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 24px;
}

.pricing-card__features li {
  font-size: 14px;
  color: var(--text-secondary);
  padding-left: 24px;
  position: relative;
}

.pricing-card__features li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: var(--green);
  font-weight: 600;
}

.pricing-guarantee {
  display: flex;
  align-items: center;
  gap: 12px;
  justify-content: center;
  margin-top: 40px;
  padding: 16px 24px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
  font-size: 14px;
  color: var(--text-secondary);
}

.pricing-guarantee__icon {
  font-size: 20px;
}

/* === ROI === */
.roi-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
  margin-bottom: 32px;
}

.roi-card {
  padding: 28px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
}

.roi-card--highlight {
  border-color: var(--green);
  background: linear-gradient(135deg, var(--green-subtle), var(--bg-card));
}

.roi-card__title {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 20px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.roi-card__row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  font-size: 14px;
  color: var(--text-secondary);
}

.roi-card__row--total {
  border-top: 1px solid var(--border);
  margin-top: 8px;
  padding-top: 12px;
  font-weight: 600;
  color: var(--text-primary);
}

.roi-card__val--negative {
  color: var(--red);
}

.roi-card__val--positive {
  color: var(--green);
  font-weight: 600;
}

.roi-note {
  text-align: center;
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* === FAQ === */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.faq-item {
  border-bottom: 1px solid var(--border);
}

.faq-item__question {
  padding: 20px 0;
  font-size: 16px;
  font-weight: 500;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: color var(--transition);
}

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

.faq-item__question::after {
  content: '+';
  font-size: 20px;
  font-weight: 300;
  color: var(--text-muted);
  transition: transform var(--transition);
  flex-shrink: 0;
  margin-left: 16px;
}

.faq-item[open] .faq-item__question::after {
  transform: rotate(45deg);
}

.faq-item__question:hover {
  color: var(--accent);
}

.faq-item__answer {
  padding: 0 0 20px;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.8;
}

/* === CTA === */
.section--cta {
  background: linear-gradient(180deg, var(--bg-elevated), var(--bg));
  text-align: center;
}

.cta__title {
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.cta__text {
  font-size: 17px;
  color: var(--text-secondary);
  margin-bottom: 36px;
  line-height: 1.7;
}

.cta-form {
  max-width: 600px;
  margin: 0 auto;
}

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

.cta-form__input {
  padding: 14px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border-strong);
  background: var(--bg-card);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 14px;
  transition: border-color var(--transition);
  outline: none;
}

.cta-form__input:focus {
  border-color: var(--accent);
}

.cta-form__input::placeholder {
  color: var(--text-muted);
}

.cta-form__note {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 12px;
}

/* === FOOTER === */
.footer {
  padding: 40px 0;
  border-top: 1px solid var(--border);
}

.footer__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer__tagline {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 4px;
}

.footer__links {
  display: flex;
  gap: 24px;
}

.footer__links a {
  font-size: 14px;
  color: var(--text-secondary);
  transition: color var(--transition);
}

.footer__links a:hover {
  color: var(--text-primary);
}

.footer__copy {
  font-size: 13px;
  color: var(--text-muted);
}

/* === RESPONSIVE === */
@media (max-width: 1024px) {
  .hero__metrics {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .feature-card--accent {
    grid-column: span 2;
  }
  
  .numbers-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .pricing-grid {
    grid-template-columns: 1fr;
    max-width: 500px;
    margin: 0 auto;
  }
  
  .pricing-card--featured {
    transform: none;
  }
}

@media (max-width: 768px) {
  .nav {
    display: none;
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 16px 24px;
    gap: 16px;
  }

  .nav.active {
    display: flex;
  }

  .burger {
    display: flex;
  }

  .header__actions .btn {
    display: none;
  }

  .hero {
    padding: 120px 0 60px;
  }

  .hero__title {
    font-size: 32px;
  }

  .hero__actions {
    flex-direction: column;
    align-items: center;
  }

  .hero__metrics {
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }

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

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

  .feature-card--accent {
    grid-column: span 1;
  }

  .numbers-grid {
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }

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

  .cta-form__row {
    grid-template-columns: 1fr;
  }

  .footer__inner {
    flex-direction: column;
    gap: 16px;
    text-align: center;
  }

  .comparison-table {
    font-size: 12px;
  }

  .comparison-table th,
  .comparison-table td {
    padding: 10px 12px;
  }
}

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

  .metric {
    flex-direction: row;
    align-items: center;
    gap: 16px;
    padding: 14px 16px;
  }

  .metric__value {
    font-size: 22px;
    flex-shrink: 0;
  }

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