:root {
  color-scheme: light;
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --accent: #22b8cf;
  --text: #152033;
  --muted: #5f6b7a;
  --surface: #ffffff;
  --background: #f5f8ff;
  --border: #dfe7f3;
  --shadow: 0 18px 50px rgba(37, 99, 235, 0.12);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans",
    "Yu Gothic", "Noto Sans JP", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 5%, rgba(34,184,207,.18), transparent 30%),
    radial-gradient(circle at 90% 0%, rgba(37,99,235,.16), transparent 34%),
    var(--background);
  line-height: 1.75;
}

a { color: var(--primary); }
a:hover { color: var(--primary-dark); }

.container {
  width: min(960px, calc(100% - 40px));
  margin: 0 auto;
}

.site-header { padding: 22px 0; }

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  color: var(--text);
  text-decoration: none;
  font-weight: 800;
  font-size: 1.15rem;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 13px;
  color: white;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  box-shadow: 0 8px 22px rgba(37,99,235,.25);
  font-size: 1.35rem;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  font-size: .94rem;
}

.nav-links a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 650;
}

.hero {
  padding: 72px 0 56px;
  text-align: center;
}

.app-symbol {
  display: grid;
  place-items: center;
  width: 112px;
  height: 112px;
  margin: 0 auto 28px;
  border-radius: 28px;
  color: white;
  font-size: 3.2rem;
  background: linear-gradient(145deg, var(--primary), var(--accent));
  box-shadow: var(--shadow);
}

h1 {
  margin: 0;
  font-size: clamp(2.6rem, 8vw, 4.7rem);
  line-height: 1.05;
  letter-spacing: -.045em;
}

.tagline {
  margin: 20px auto 0;
  font-size: clamp(1.2rem, 4vw, 1.65rem);
  font-weight: 750;
}

.lead {
  max-width: 680px;
  margin: 18px auto 0;
  color: var(--muted);
  font-size: 1.05rem;
}

.actions {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 30px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 22px;
  border-radius: 14px;
  text-decoration: none;
  font-weight: 750;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
}

.button.primary {
  color: #fff;
  border-color: transparent;
  background: var(--primary);
}

.section { padding: 32px 0 72px; }
.section-title { text-align: center; margin-bottom: 30px; }
.section-title h2 { margin: 0; font-size: 2rem; }
.section-title p { color: var(--muted); }

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}

.card {
  padding: 25px;
  border: 1px solid var(--border);
  border-radius: 22px;
  background: rgba(255,255,255,.88);
  box-shadow: 0 10px 35px rgba(27,55,94,.06);
  backdrop-filter: blur(14px);
}

.card-icon { font-size: 1.7rem; }
.card h3 { margin: 10px 0 6px; }
.card p { margin: 0; color: var(--muted); }

.document {
  margin: 28px auto 70px;
  padding: clamp(24px, 6vw, 54px);
  border: 1px solid var(--border);
  border-radius: 26px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.document h1 {
  font-size: clamp(2rem, 7vw, 3.2rem);
  margin-bottom: 8px;
}

.document h2 {
  margin-top: 2.3em;
  padding-bottom: .35em;
  border-bottom: 1px solid var(--border);
  font-size: 1.3rem;
}

.document h3 { margin-top: 1.7em; }
.document p, .document li { color: #334155; }
.document ul { padding-left: 1.4em; }
.updated { color: var(--muted); font-size: .92rem; }

.note {
  padding: 16px 18px;
  border-left: 4px solid var(--primary);
  border-radius: 10px;
  background: #f1f6ff;
}

.site-footer {
  padding: 30px 0 45px;
  color: var(--muted);
  font-size: .9rem;
  text-align: center;
}

.footer-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 10px;
}

@media (max-width: 760px) {
  .nav { align-items: flex-start; }
  .nav-links { justify-content: flex-end; gap: 10px 14px; }
  .hero { padding-top: 44px; }
  .grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .container { width: min(100% - 24px, 960px); }
  .brand span:last-child { display: none; }
  .nav-links { font-size: .86rem; }
  .document { border-radius: 18px; }
}