:root {
  --color-bg: #ffffff;
  --color-text: #1d1d1f;
  --color-text-secondary: #6e6e73;
  --color-border: #d2d2d7;
  --color-accent: #0071e3;
  --color-surface: #f5f5f7;
  --max-width: 980px;
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Hiragino Sans",
    "Hiragino Kaku Gothic ProN", "Segoe UI", Roboto, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

a:hover {
  text-decoration: underline;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.8);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--color-border);
}

.nav {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  font-weight: 600;
  font-size: 17px;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.nav-links {
  display: flex;
  gap: 28px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links a {
  color: var(--color-text);
  font-size: 14px;
}

.nav-links a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.nav-toggle {
  display: none;
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.hero {
  text-align: center;
  padding: 96px 24px 64px;
}

.hero h1 {
  font-size: 56px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 16px;
}

.hero p {
  font-size: 21px;
  color: var(--color-text-secondary);
  max-width: 640px;
  margin: 0 auto;
}

section {
  padding: 48px 0;
  border-top: 1px solid var(--color-border);
}

section h2 {
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.01em;
  text-align: center;
  margin: 0 0 40px;
}

.apps-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.app-card {
  background: var(--color-surface);
  border-radius: 18px;
  padding: 32px;
  text-align: center;
  transition: transform 0.2s ease;
}

.app-card:hover {
  transform: translateY(-4px);
}

.app-icon {
  display: block;
  width: 72px;
  height: 72px;
  border-radius: 18px;
  margin: 0 auto 20px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
}

.app-card h3 {
  font-size: 20px;
  margin: 0 0 8px;
}

.app-card p {
  color: var(--color-text-secondary);
  font-size: 15px;
  margin: 0;
}

.links-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
}

.link-card {
  display: block;
  background: var(--color-surface);
  border-radius: 14px;
  padding: 24px;
  text-align: center;
  color: var(--color-text);
  font-weight: 600;
  font-size: 16px;
  transition: background 0.2s ease;
}

.link-card:hover {
  background: #e8e8ed;
  text-decoration: none;
}

.page-hero {
  padding: 72px 24px 32px;
  text-align: center;
  border-top: none;
}

.page-hero h1 {
  font-size: 40px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 8px;
}

.page-hero p {
  color: var(--color-text-secondary);
  font-size: 15px;
}

.doc {
  padding: 16px 0 96px;
  border-top: none;
  max-width: 760px;
  margin: 0 auto;
}

.doc h2 {
  font-size: 22px;
  text-align: left;
  margin: 40px 0 12px;
}

.doc h2:first-child {
  margin-top: 0;
}

.doc p,
.doc li {
  color: var(--color-text);
  font-size: 16px;
}

.doc ul {
  padding-left: 20px;
}

.doc .updated {
  color: var(--color-text-secondary);
  font-size: 14px;
  margin-top: -8px;
}

.contact-box {
  background: var(--color-surface);
  border-radius: 14px;
  padding: 28px;
  text-align: center;
  margin-top: 24px;
}

.contact-box .email {
  font-size: 19px;
  font-weight: 600;
}

.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 32px 24px;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 12px;
}

.site-footer a {
  color: var(--color-text-secondary);
  margin: 0 8px;
}

@media (max-width: 640px) {
  .hero {
    padding: 64px 20px 40px;
  }

  .hero h1 {
    font-size: 36px;
  }

  .hero p {
    font-size: 17px;
  }

  section h2 {
    font-size: 26px;
  }

  .page-hero h1 {
    font-size: 30px;
  }
}

@media (max-width: 480px) {
  .nav {
    flex-direction: column;
    align-items: center;
    height: auto;
    padding: 12px 16px;
    gap: 8px;
  }

  .nav-links {
    gap: 14px;
  }

  .nav-links a {
    font-size: 13px;
  }
}