/* ========================================
   BioTwin - Main Stylesheet
   Colors: NVIDIA Green (#76B900) + Dark Gray (#1A1A1A)
   ======================================== */

@import url('https://fonts.googleapis.com/css2?family=Exo+2:wght@300;400;500;600;700;800;900&family=DM+Sans:wght@300;400;500;600&display=swap');

/* ---- CSS Variables ---- */
:root {
  --green:         #76B900;
  --green-bright:  #8DD400;
  --green-dim:     #4E7A00;
  --dark:          #1A1A1A;
  --dark-mid:      #242424;
  --dark-card:     #2E2E2E;
  --dark-border:   #3A3A3A;
  --white:         #FFFFFF;
  --gray-light:    #AAAAAA;
  --gray-text:     #CCCCCC;
  --font-display:  'Exo 2', sans-serif;
  --font-body:     'DM Sans', sans-serif;
  --radius:        12px;
  --radius-lg:     20px;
  --transition:    0.3s ease;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--dark);
  color: var(--gray-text);
  line-height: 1.65;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }
a { text-decoration: none; color: inherit; }
ul { list-style: none; }

/* ---- Typography ---- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  color: var(--white);
  line-height: 1.2;
}

h1 { font-size: clamp(2.4rem, 5vw, 4rem); font-weight: 800; }
h2 { font-size: clamp(1.8rem, 3.5vw, 2.8rem); font-weight: 700; }
h3 { font-size: 1.25rem; font-weight: 600; }

.section-label {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--green);
  margin-bottom: 0.6rem;
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.75rem;
  border-radius: 6px;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.9rem;
  letter-spacing: 0.04em;
  cursor: pointer;
  border: none;
  transition: var(--transition);
}

.btn-primary {
  background: var(--green);
  color: var(--dark);
}
.btn-primary:hover { background: var(--green-bright); transform: translateY(-2px); box-shadow: 0 8px 24px rgba(118,185,0,0.35); }

.btn-outline {
  background: transparent;
  color: var(--white);
  border: 1.5px solid var(--dark-border);
}
.btn-outline:hover { border-color: var(--green); color: var(--green); transform: translateY(-2px); }

.btn-ghost {
  background: rgba(118,185,0,0.1);
  color: var(--green);
  border: 1.5px solid rgba(118,185,0,0.3);
}
.btn-ghost:hover { background: var(--green); color: var(--dark); }

/* ---- Layout ---- */
.container { max-width: 1160px; margin: 0 auto; padding: 0 1.5rem; }
.section    { padding: 80px 0; }
.section-sm { padding: 50px 0; }

/* ---- Divider ---- */
.divider {
  width: 48px; height: 3px;
  background: var(--green);
  border-radius: 2px;
  margin: 1rem 0 1.5rem;
}

/* ---- Navbar ---- */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 2rem;
  height: 68px;
  background: rgba(26,26,26,0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(118,185,0,0.12);
  transition: var(--transition);
}

.navbar.scrolled {
  background: rgba(20,20,20,0.98);
  box-shadow: 0 4px 20px rgba(0,0,0,0.4);
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--white);
}

.nav-brand-icon {
  width: 34px; height: 34px;
  background: var(--green);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.nav-brand-icon svg { width: 20px; height: 20px; fill: var(--dark); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--gray-light);
  transition: color var(--transition);
  position: relative;
}
.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px; left: 0; right: 100%;
  height: 2px;
  background: var(--green);
  transition: right var(--transition);
}
.nav-links a:hover { color: var(--white); }
.nav-links a:hover::after { right: 0; }

.nav-cta { display: flex; gap: 0.75rem; align-items: center; }

.hamburger { display: none; flex-direction: column; gap: 5px; cursor: pointer; padding: 4px; }
.hamburger span { display: block; width: 22px; height: 2px; background: var(--white); border-radius: 2px; transition: var(--transition); }

/* ---- Hero ---- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  padding-top: 68px;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 60% 60% at 70% 50%, rgba(118,185,0,0.08) 0%, transparent 70%),
    radial-gradient(ellipse 40% 40% at 20% 80%, rgba(118,185,0,0.05) 0%, transparent 60%),
    var(--dark);
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(118,185,0,0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(118,185,0,0.05) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 80% 80% at center, black 30%, transparent 80%);
}

.hero-content {
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.85rem;
  background: rgba(118,185,0,0.1);
  border: 1px solid rgba(118,185,0,0.25);
  border-radius: 30px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--green);
  margin-bottom: 1.25rem;
}

.hero-badge .dot { width: 6px; height: 6px; background: var(--green); border-radius: 50%; animation: pulse 2s infinite; }

.hero-title { margin-bottom: 1.25rem; }
.hero-title .accent { color: var(--green); }

.hero-desc { font-size: 1.05rem; color: var(--gray-light); max-width: 480px; margin-bottom: 2rem; }

.hero-actions { display: flex; gap: 1rem; flex-wrap: wrap; margin-bottom: 2.5rem; }

.hero-stats { display: flex; gap: 2rem; }
.hero-stat-num { font-family: var(--font-display); font-size: 1.5rem; font-weight: 800; color: var(--white); }
.hero-stat-num span { color: var(--green); }
.hero-stat-lbl { font-size: 0.78rem; color: var(--gray-light); margin-top: 0.1rem; }

/* Phone Mockup */
.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

.phone-glow {
  position: absolute;
  width: 300px; height: 300px;
  background: radial-gradient(circle, rgba(118,185,0,0.2) 0%, transparent 70%);
  border-radius: 50%;
}

.phone-mockup {
  width: 240px;
  background: var(--dark-mid);
  border-radius: 36px;
  border: 2px solid var(--dark-border);
  overflow: hidden;
  position: relative;
  box-shadow: 0 30px 80px rgba(0,0,0,0.6), 0 0 0 1px rgba(118,185,0,0.15), inset 0 1px 0 rgba(255,255,255,0.05);
  animation: float 4s ease-in-out infinite;
}

.phone-screen {
  padding: 20px 16px;
  background: var(--dark-mid);
}

.phone-notch {
  width: 80px; height: 20px;
  background: var(--dark);
  border-radius: 0 0 12px 12px;
  margin: 0 auto 16px;
}

.phone-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 16px; }
.phone-header-title { font-family: var(--font-display); font-size: 0.85rem; font-weight: 700; color: var(--white); }
.phone-header-icon { width: 28px; height: 28px; background: rgba(118,185,0,0.15); border-radius: 8px; display: flex; align-items: center; justify-content: center; }

.heart-rate-widget {
  background: var(--dark-card);
  border-radius: 12px;
  padding: 14px;
  margin-bottom: 12px;
}

.hr-label { font-size: 0.65rem; color: var(--gray-light); text-transform: uppercase; letter-spacing: 0.1em; }
.hr-value { font-family: var(--font-display); font-size: 2.2rem; font-weight: 800; color: var(--green); line-height: 1; }
.hr-unit { font-size: 0.7rem; color: var(--gray-light); }

.hr-wave { margin-top: 8px; }
.hr-wave svg { width: 100%; height: 36px; }

.metric-row { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-bottom: 12px; }
.metric-card {
  background: var(--dark-card);
  border-radius: 10px;
  padding: 12px;
  border: 1px solid var(--dark-border);
}
.metric-icon { font-size: 1.1rem; margin-bottom: 4px; }
.metric-val { font-family: var(--font-display); font-size: 1rem; font-weight: 700; color: var(--white); }
.metric-lbl { font-size: 0.6rem; color: var(--gray-light); }

.activity-bar {
  background: var(--dark-card);
  border-radius: 10px;
  padding: 12px;
}
.activity-label { font-size: 0.65rem; color: var(--gray-light); margin-bottom: 8px; }
.bar-track { background: var(--dark-border); border-radius: 4px; height: 6px; }
.bar-fill  { background: linear-gradient(90deg, var(--green-dim), var(--green)); border-radius: 4px; height: 6px; width: 72%; }

/* ---- Trusted ---- */
.trusted { padding: 40px 0; border-top: 1px solid var(--dark-border); border-bottom: 1px solid var(--dark-border); }
.trusted-inner { display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 2.5rem 3.5rem; }
.trusted-label { font-size: 0.78rem; color: var(--gray-light); letter-spacing: 0.1em; text-transform: uppercase; }
.trusted-logos { display: flex; flex-wrap: wrap; align-items: center; gap: 2.5rem; }
.trusted-logo { font-family: var(--font-display); font-size: 1rem; font-weight: 700; color: var(--dark-border); letter-spacing: 0.05em; transition: color var(--transition); }
.trusted-logo:hover { color: var(--gray-light); }

/* ---- Features ---- */
.features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; margin-top: 3rem; }

.feature-card {
  background: var(--dark-mid);
  border: 1px solid var(--dark-border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}
.feature-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--green), transparent);
  opacity: 0;
  transition: var(--transition);
}
.feature-card:hover { border-color: rgba(118,185,0,0.35); transform: translateY(-4px); box-shadow: 0 12px 40px rgba(0,0,0,0.3); }
.feature-card:hover::before { opacity: 1; }

.feature-icon {
  width: 52px; height: 52px;
  background: rgba(118,185,0,0.1);
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 1.25rem;
  border: 1px solid rgba(118,185,0,0.2);
}

.feature-card h3 { margin-bottom: 0.65rem; font-size: 1.1rem; }
.feature-card p  { font-size: 0.88rem; color: var(--gray-light); line-height: 1.7; }

/* ---- How It Works ---- */
.howitworks { background: var(--dark-mid); }

.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 2rem; margin-top: 3rem; position: relative; }
.steps::before {
  content: '';
  position: absolute;
  top: 28px; left: calc(16.6% + 1rem); right: calc(16.6% + 1rem);
  height: 1px;
  background: linear-gradient(90deg, var(--dark-border), var(--green), var(--dark-border));
}

.step { text-align: center; position: relative; }
.step-num {
  width: 56px; height: 56px;
  border-radius: 50%;
  background: var(--dark);
  border: 2px solid var(--green);
  color: var(--green);
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.1rem;
  display: flex; align-items: center; justify-content: center;
  margin: 0 auto 1.25rem;
  position: relative; z-index: 2;
}
.step h3 { margin-bottom: 0.6rem; }
.step p { font-size: 0.88rem; color: var(--gray-light); }

/* ---- App Section ---- */
.app-section { background: var(--dark); }

.app-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 5rem;
  align-items: center;
}

.app-feature-list { margin: 1.5rem 0 2rem; display: flex; flex-direction: column; gap: 0.9rem; }
.app-feature-item { display: flex; gap: 0.75rem; align-items: flex-start; }
.app-feature-check {
  width: 22px; height: 22px;
  background: rgba(118,185,0,0.15);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  margin-top: 1px;
}
.app-feature-check svg { width: 12px; height: 12px; }
.app-feature-item p { font-size: 0.9rem; color: var(--gray-light); }

.download-btns { display: flex; gap: 1rem; flex-wrap: wrap; }

.store-btn {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem 1.25rem;
  background: var(--dark-card);
  border: 1px solid var(--dark-border);
  border-radius: 10px;
  transition: var(--transition);
  cursor: pointer;
}
.store-btn:hover { border-color: var(--green); transform: translateY(-2px); }
.store-btn-icon { font-size: 1.4rem; }
.store-btn-txt span { display: block; }
.store-btn-txt .small { font-size: 0.65rem; color: var(--gray-light); }
.store-btn-txt .big  { font-family: var(--font-display); font-size: 0.9rem; font-weight: 700; color: var(--white); }

/* Dual phones */
.app-phones {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  align-items: flex-end;
}

.phone-mockup.sm {
  width: 190px;
  transform: translateY(20px);
  opacity: 0.75;
}

/* ---- Stats Section ---- */
.stats-section {
  background: var(--dark-mid);
  border-top: 1px solid var(--dark-border);
  border-bottom: 1px solid var(--dark-border);
}

.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 2rem; }

.stat-item { text-align: center; padding: 2rem 1rem; }
.stat-number {
  font-family: var(--font-display);
  font-size: 2.8rem;
  font-weight: 900;
  color: var(--green);
  line-height: 1;
  margin-bottom: 0.4rem;
}
.stat-label { font-size: 0.875rem; color: var(--gray-light); }

/* ---- Testimonials ---- */
.testimonials-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; margin-top: 3rem; }

.testimonial-card {
  background: var(--dark-mid);
  border: 1px solid var(--dark-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  transition: var(--transition);
}
.testimonial-card:hover { border-color: rgba(118,185,0,0.3); transform: translateY(-3px); }

.stars { display: flex; gap: 3px; margin-bottom: 1rem; }
.stars span { color: var(--green); font-size: 0.9rem; }

.testimonial-text { font-size: 0.9rem; color: var(--gray-text); line-height: 1.75; margin-bottom: 1.25rem; font-style: italic; }

.testimonial-author { display: flex; align-items: center; gap: 0.75rem; }
.author-avatar {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--dark-card);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--green);
  border: 2px solid rgba(118,185,0,0.3);
}
.author-name { font-weight: 600; font-size: 0.875rem; color: var(--white); }
.author-role { font-size: 0.75rem; color: var(--gray-light); }

/* ---- Pricing ---- */
.pricing { background: var(--dark-mid); }

.pricing-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; margin-top: 3rem; align-items: start; }

.pricing-card {
  background: var(--dark);
  border: 1px solid var(--dark-border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  position: relative;
  transition: var(--transition);
}
.pricing-card:hover { border-color: rgba(118,185,0,0.35); transform: translateY(-4px); }
.pricing-card.featured {
  border-color: var(--green);
  background: linear-gradient(145deg, rgba(118,185,0,0.06), var(--dark));
}

.pricing-badge {
  position: absolute;
  top: -12px; left: 50%; transform: translateX(-50%);
  background: var(--green);
  color: var(--dark);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.3rem 1rem;
  border-radius: 20px;
}

.pricing-plan  { font-size: 0.8rem; color: var(--gray-light); text-transform: uppercase; letter-spacing: 0.12em; margin-bottom: 0.5rem; }
.pricing-price { font-family: var(--font-display); font-size: 2.8rem; font-weight: 900; color: var(--white); line-height: 1; }
.pricing-price sup { font-size: 1.2rem; vertical-align: super; margin-right: 2px; color: var(--green); }
.pricing-price .period { font-size: 0.9rem; color: var(--gray-light); font-weight: 400; }
.pricing-desc { font-size: 0.85rem; color: var(--gray-light); margin: 0.75rem 0 1.5rem; }

.pricing-features { display: flex; flex-direction: column; gap: 0.7rem; margin-bottom: 2rem; }
.pricing-feature { display: flex; align-items: center; gap: 0.6rem; font-size: 0.875rem; color: var(--gray-text); }
.pricing-feature .check { color: var(--green); font-size: 1rem; }
.pricing-feature .cross { color: var(--dark-border); font-size: 1rem; }

/* ---- CTA ---- */
.cta-section {
  background: linear-gradient(135deg, rgba(118,185,0,0.08) 0%, var(--dark) 50%, rgba(118,185,0,0.05) 100%);
  border-top: 1px solid rgba(118,185,0,0.15);
  text-align: center;
}

.cta-section h2 { margin-bottom: 1rem; }
.cta-section p  { font-size: 1.05rem; color: var(--gray-light); max-width: 560px; margin: 0 auto 2.5rem; }
.cta-actions { display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap; }

/* ---- Footer ---- */
.footer {
  background: #111;
  border-top: 1px solid var(--dark-border);
  padding: 50px 0 0;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 3rem;
  padding-bottom: 3rem;
  border-bottom: 1px solid var(--dark-border);
}

.footer-brand p { font-size: 0.875rem; color: var(--gray-light); margin: 1rem 0 1.5rem; max-width: 260px; line-height: 1.7; }

.social-links { display: flex; gap: 0.75rem; }
.social-link {
  width: 36px; height: 36px;
  background: var(--dark-card);
  border: 1px solid var(--dark-border);
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  color: var(--gray-light);
  font-size: 0.85rem;
  transition: var(--transition);
}
.social-link:hover { background: var(--green); color: var(--dark); border-color: var(--green); }

.footer-col h4 { font-size: 0.875rem; font-weight: 700; color: var(--white); margin-bottom: 1.25rem; text-transform: uppercase; letter-spacing: 0.08em; }
.footer-col ul { display: flex; flex-direction: column; gap: 0.65rem; }
.footer-col a { font-size: 0.875rem; color: var(--gray-light); transition: color var(--transition); }
.footer-col a:hover { color: var(--green); }

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 0;
  font-size: 0.8rem;
  color: var(--gray-light);
  flex-wrap: wrap;
  gap: 0.5rem;
}

/* ---- Animations ---- */
@keyframes float {
  0%, 100% { transform: translateY(0px); }
  50%       { transform: translateY(-12px); }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50%       { opacity: 0.4; }
}

.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---- Responsive ---- */
@media (max-width: 1024px) {
  .hero-content      { gap: 2.5rem; }
  .features-grid     { grid-template-columns: repeat(2, 1fr); }
  .testimonials-grid { grid-template-columns: repeat(2, 1fr); }
  .pricing-grid      { grid-template-columns: 1fr; max-width: 420px; margin-left: auto; margin-right: auto; }
  .footer-grid       { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .nav-links, .nav-cta { display: none; }
  .hamburger { display: flex; }

  .hero-content    { grid-template-columns: 1fr; text-align: center; }
  .hero-desc       { max-width: 100%; }
  .hero-actions    { justify-content: center; }
  .hero-stats      { justify-content: center; }
  .hero-visual     { order: -1; }

  .features-grid     { grid-template-columns: 1fr; }
  .steps             { grid-template-columns: 1fr; }
  .steps::before     { display: none; }
  .app-content       { grid-template-columns: 1fr; text-align: center; }
  .app-phones        { justify-content: center; }
  .stats-grid        { grid-template-columns: repeat(2, 1fr); }
  .testimonials-grid { grid-template-columns: 1fr; }
  .footer-grid       { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 480px) {
  .stats-grid  { grid-template-columns: 1fr 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .hero-stats  { gap: 1.5rem; }
}