:root {
  --color-bg: #f8faff;
  --color-surface: #ffffff;
  --color-border: #d6dfe8;
  --color-text: #1a1a1a;
  --color-text-muted: #808080;
  --color-accent: #2666a6;
  --color-accent-hover: #1d5490;
  --color-accent-light: #eaf2fa;
  --color-o2: #4073d9;
  --color-co2: #ffb333;
  --color-free: #6666cc;
  --color-shadow: rgba(0, 0, 0, 0.08);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: "SF Mono", "Fira Code", "Fira Mono", monospace;
  --max-width: 960px;
  --radius: 12px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

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

/* Navigation */
.site-header {
  position: sticky;
  top: 0;
  background: var(--color-accent);
  color: #fff;
  z-index: 100;
  box-shadow: 0 2px 4px var(--color-shadow);
}

.site-header nav {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.75rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: #fff;
  font-weight: 700;
  font-size: 1.25rem;
}

.nav-logo:hover {
  color: #fff;
}

.nav-links {
  display: flex;
  gap: 1.5rem;
}

.nav-links a {
  color: rgba(255, 255, 255, 0.85);
  font-size: 0.875rem;
  font-weight: 500;
}

.nav-links a:hover {
  color: #fff;
}

/* Main content */
main {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  width: 100%;
}

/* Hero */
.hero {
  text-align: center;
  padding: 4rem 0 3rem;
}

.hero-logo {
  width: 160px;
  height: 160px;
  margin-bottom: 1.5rem;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
  color: var(--color-accent);
}

.hero-tagline {
  font-size: 1.25rem;
  color: var(--color-text-muted);
  margin-bottom: 1rem;
}

.hero-description {
  max-width: 520px;
  margin: 0 auto 2rem;
  color: var(--color-text-muted);
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.9375rem;
  transition: background 0.15s, color 0.15s, box-shadow 0.15s;
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
  box-shadow: 0 2px 4px var(--color-shadow);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  color: #fff;
  box-shadow: 0 4px 8px var(--color-shadow);
}

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-accent);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  background: var(--color-accent-light);
  color: var(--color-accent-hover);
}

/* Features */
.features {
  padding: 3rem 0;
}

.features h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  text-align: center;
  color: var(--color-text);
}

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

.feature-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: 0 2px 4px var(--color-shadow);
}

.feature-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  color: var(--color-accent);
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

.feature-card:nth-child(1) h3 { color: var(--color-o2); }
.feature-card:nth-child(2) h3 { color: var(--color-co2); }
.feature-card:nth-child(3) h3 { color: var(--color-free); }
.feature-card:nth-child(4) h3 { color: var(--color-accent); }

/* Screenshots */
.screenshots {
  padding: 3rem 0;
}

.screenshots h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  text-align: center;
}

.screenshot-gallery {
  display: flex;
  gap: 1rem;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  padding-bottom: 1rem;
  -webkit-overflow-scrolling: touch;
}

.screenshot-gallery figure {
  flex: 0 0 auto;
  scroll-snap-align: center;
}

.screenshot-gallery img {
  height: 480px;
  width: auto;
  border-radius: var(--radius);
  box-shadow: 0 2px 8px var(--color-shadow);
}

/* Page content (changelog, privacy, etc.) */
.page {
  padding: 3rem 0;
  max-width: 720px;
  margin: 0 auto;
}

.page h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  color: var(--color-accent);
}

.page h2 {
  font-size: 1.375rem;
  font-weight: 600;
  margin-top: 2rem;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}

.page h3 {
  font-size: 1.125rem;
  font-weight: 600;
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
}

.page p,
.page ul,
.page ol {
  margin-bottom: 1rem;
  color: var(--color-text-muted);
}

.page ul,
.page ol {
  padding-left: 1.5rem;
}

.page li {
  margin-bottom: 0.25rem;
}

.page code {
  font-family: var(--font-mono);
  background: var(--color-accent-light);
  padding: 0.125rem 0.375rem;
  border-radius: 4px;
  font-size: 0.875em;
}

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

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 1.5rem;
  text-align: center;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.site-footer a {
  color: var(--color-text-muted);
}

.site-footer a:hover {
  color: var(--color-accent);
}

/* Responsive */
@media (max-width: 640px) {
  .hero-logo {
    width: 120px;
    height: 120px;
  }

  .hero h1 {
    font-size: 2rem;
  }

  .hero-tagline {
    font-size: 1.0625rem;
  }

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

  .screenshot-gallery img {
    height: 360px;
  }
}