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

:root {
  /* Colors */
  --c-bg: #fafafa;
  --c-surface: #ffffff;
  --c-text: #1a1a1a;
  --c-text-secondary: #555;
  --c-text-muted: #888;
  --c-accent: #2563eb;
  --c-accent-hover: #1d4ed8;
  --c-border: #e5e5e5;
  --c-border-light: #f0f0f0;
  --c-code-bg: #f5f5f5;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;
  --space-5xl: 8rem;

  /* Layout */
  --max-width: 1120px;
  --max-width-narrow: 720px;

  /* Misc */
  --radius: 8px;
  --radius-lg: 12px;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.06);
  --transition: 150ms ease;
}

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

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--c-text);
  background: var(--c-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--c-accent);
  text-decoration: none;
  transition: color var(--transition);
}

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

/* ===== Layout ===== */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

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

section {
  padding: var(--space-4xl) 0;
}

/* ===== Typography ===== */
h1, h2, h3, h4 {
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--c-text);
}

h1 {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 700;
}

h2 {
  font-size: clamp(1.5rem, 3.5vw, 2.25rem);
  font-weight: 700;
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
}

h4 {
  font-size: 1.1rem;
  font-weight: 600;
}

p {
  color: var(--c-text-secondary);
}

.label {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--c-accent);
}

/* ===== Navigation ===== */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(250, 250, 250, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--c-border-light);
}

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

.nav__logo {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--c-text);
  letter-spacing: -0.03em;
}

.nav__logo:hover {
  color: var(--c-text);
}

.nav__links {
  display: flex;
  gap: var(--space-xl);
  list-style: none;
}

.nav__links a {
  font-size: 0.9rem;
  color: var(--c-text-secondary);
  font-weight: 500;
  transition: color var(--transition);
}

.nav__links a:hover {
  color: var(--c-text);
}

.nav__hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
}

.nav__hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--c-text);
  margin: 4px 0;
  transition: transform var(--transition), opacity var(--transition);
}

/* Mobile nav */
@media (max-width: 640px) {
  .nav__hamburger {
    display: block;
  }

  .nav__links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--c-bg);
    border-bottom: 1px solid var(--c-border);
    padding: var(--space-md) var(--space-lg);
    gap: var(--space-md);
  }

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

  .nav__hamburger.is-open span:nth-child(1) {
    transform: rotate(45deg) translate(3px, 3px);
  }

  .nav__hamburger.is-open span:nth-child(2) {
    opacity: 0;
  }

  .nav__hamburger.is-open span:nth-child(3) {
    transform: rotate(-45deg) translate(4px, -4px);
  }
}

/* ===== Hero ===== */
.hero {
  padding: var(--space-5xl) 0 var(--space-4xl);
  text-align: center;
}

.hero h1 {
  max-width: 720px;
  margin: 0 auto var(--space-lg);
}

.hero__sub {
  max-width: 560px;
  margin: 0 auto;
  font-size: 1.125rem;
  line-height: 1.7;
  color: var(--c-text-secondary);
}

/* ===== How It Works ===== */
.steps {
  background: var(--c-surface);
  border-top: 1px solid var(--c-border-light);
  border-bottom: 1px solid var(--c-border-light);
}

.steps__header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.steps__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-xl);
}

.step {
  text-align: center;
}

.step__number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--c-bg);
  border: 1px solid var(--c-border);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--c-accent);
  margin-bottom: var(--space-md);
}

.step h3 {
  margin-bottom: var(--space-sm);
}

.step p {
  font-size: 0.9rem;
}

@media (max-width: 800px) {
  .steps__grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-2xl);
  }
}

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

/* ===== Pillars ===== */
.pillars__header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.pillars__grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-xl);
}

.pillar {
  padding: var(--space-xl);
  background: var(--c-surface);
  border: 1px solid var(--c-border-light);
  border-radius: var(--radius-lg);
}

.pillar .label {
  margin-bottom: var(--space-sm);
}

.pillar h3 {
  margin-bottom: var(--space-md);
}

.pillar p {
  font-size: 0.9rem;
  line-height: 1.65;
}

@media (max-width: 800px) {
  .pillars__grid {
    grid-template-columns: 1fr;
  }
}

/* ===== Science Teaser ===== */
.science-teaser {
  background: var(--c-surface);
  border-top: 1px solid var(--c-border-light);
  border-bottom: 1px solid var(--c-border-light);
}

.science-teaser__inner {
  max-width: var(--max-width-narrow);
  margin: 0 auto;
}

.science-teaser h2 {
  margin-bottom: var(--space-lg);
}

.science-teaser p {
  font-size: 1.05rem;
  line-height: 1.75;
  margin-bottom: var(--space-md);
}

.science-teaser .link-arrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  font-weight: 600;
  margin-top: var(--space-md);
}

.link-arrow::after {
  content: '\2192';
  transition: transform var(--transition);
}

.link-arrow:hover::after {
  transform: translateX(3px);
}

/* ===== FAQ ===== */
.faq__header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.faq__list {
  max-width: var(--max-width-narrow);
  margin: 0 auto;
}

.faq__item {
  border-bottom: 1px solid var(--c-border);
}

.faq__question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg) 0;
  background: none;
  border: none;
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  color: var(--c-text);
  text-align: left;
  gap: var(--space-md);
}

.faq__icon {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  position: relative;
  transition: transform var(--transition);
}

.faq__icon::before,
.faq__icon::after {
  content: '';
  position: absolute;
  background: var(--c-text-muted);
  border-radius: 1px;
}

.faq__icon::before {
  top: 50%;
  left: 0;
  right: 0;
  height: 2px;
  transform: translateY(-50%);
}

.faq__icon::after {
  left: 50%;
  top: 0;
  bottom: 0;
  width: 2px;
  transform: translateX(-50%);
  transition: transform var(--transition);
}

.faq__item.is-open .faq__icon::after {
  transform: translateX(-50%) scaleY(0);
}

.faq__answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 200ms ease;
}

.faq__answer p {
  padding-bottom: var(--space-lg);
  font-size: 0.95rem;
  line-height: 1.65;
}

/* ===== Footer ===== */
.footer {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--c-border-light);
}

.footer__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.footer__links {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
}

.footer__links a {
  font-size: 0.875rem;
  color: var(--c-text-muted);
  font-weight: 500;
}

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

.footer__copy {
  font-size: 0.8rem;
  color: var(--c-text-muted);
}

/* ===== Science Page ===== */
.page-header {
  padding: var(--space-4xl) 0 var(--space-2xl);
  text-align: center;
}

.page-header p {
  max-width: 560px;
  margin: var(--space-md) auto 0;
  font-size: 1.1rem;
}

.prose {
  max-width: var(--max-width-narrow);
  margin: 0 auto;
  padding-bottom: var(--space-4xl);
}

.prose h2 {
  margin-top: var(--space-3xl);
  margin-bottom: var(--space-md);
}

.prose h3 {
  margin-top: var(--space-2xl);
  margin-bottom: var(--space-sm);
}

.prose p {
  margin-bottom: var(--space-md);
  font-size: 1.025rem;
  line-height: 1.75;
}

.prose ul {
  margin-bottom: var(--space-md);
  padding-left: var(--space-lg);
}

.prose li {
  margin-bottom: var(--space-sm);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--c-text-secondary);
}

.prose blockquote {
  margin: var(--space-2xl) 0;
  padding: var(--space-lg) var(--space-xl);
  border-left: 3px solid var(--c-accent);
  background: var(--c-surface);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.prose blockquote p {
  font-size: 1.05rem;
  font-style: italic;
  color: var(--c-text);
}

.prose a {
  text-decoration: underline;
  text-underline-offset: 2px;
}

/* ===== Privacy Page ===== */
.privacy-content table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-lg) 0;
  font-size: 0.9rem;
}

.privacy-content th,
.privacy-content td {
  text-align: left;
  padding: var(--space-sm) var(--space-md);
  border-bottom: 1px solid var(--c-border);
  color: var(--c-text-secondary);
  vertical-align: top;
}

.privacy-content th {
  font-weight: 600;
  color: var(--c-text);
  background: var(--c-code-bg);
}

.privacy-content h3 {
  margin-top: var(--space-2xl);
}

/* ===== Utilities ===== */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}