:root {
  --brand: #FFE100;
  --brand-deep: #FFC400;
  --ink: #111111;
  --bg: #F2F2F4;
  --paper: #FFFFFF;
  --line: #D9D9DE;
  --muted: #6B6B6B;
  --info: #2F80ED;
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Kaku Gothic ProN",
    "Hiragino Sans", "Yu Gothic", Meiryo, system-ui, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--info); }

.header {
  background: var(--brand);
  border-bottom: 1px solid var(--brand-deep);
}

.header-inner {
  max-width: 760px;
  margin: 0 auto;
  padding: 18px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.brand {
  font-weight: 800;
  font-size: 20px;
  color: var(--ink);
  text-decoration: none;
  letter-spacing: 0.02em;
}

.lang-toggle {
  display: inline-flex;
  background: rgba(17, 17, 17, 0.08);
  border-radius: 999px;
  padding: 3px;
}

.lang-toggle button {
  border: 0;
  background: transparent;
  color: var(--ink);
  font-size: 13px;
  font-weight: 700;
  padding: 6px 14px;
  border-radius: 999px;
  cursor: pointer;
}

.lang-toggle button.active {
  background: var(--ink);
  color: #fff;
}

main {
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

h1 {
  font-size: 26px;
  font-weight: 800;
  margin: 8px 0 4px;
}

.updated {
  color: var(--muted);
  font-size: 13px;
  margin: 0 0 28px;
}

section.doc {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 24px 22px;
}

h2 {
  font-size: 17px;
  font-weight: 700;
  margin: 28px 0 8px;
}

h2:first-of-type { margin-top: 4px; }

p { margin: 0 0 10px; font-size: 15px; }

.contact {
  font-size: 14px;
  color: var(--muted);
}

/* Landing */
.hero {
  text-align: center;
  padding: 48px 0 24px;
}

.hero h1 { font-size: 32px; }

.hero p { color: var(--muted); }

.cards {
  display: grid;
  gap: 14px;
  margin-top: 28px;
}

.card {
  display: block;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 20px 22px;
  text-decoration: none;
  color: var(--ink);
}

.card:hover { border-color: var(--brand-deep); }

.card .title { font-weight: 700; font-size: 17px; }

.card .sub { color: var(--muted); font-size: 13px; margin-top: 2px; }

footer {
  max-width: 760px;
  margin: 0 auto;
  padding: 24px 20px 48px;
  color: var(--muted);
  font-size: 12px;
  text-align: center;
}

[data-lang] { display: none; }
[data-lang].active { display: block; }

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #F2F2F4;
    --bg: #121214;
    --paper: #1E1E20;
    --line: #3A3A3D;
    --muted: #ADADB3;
  }
  .brand, .lang-toggle button { color: #111111; }
  .lang-toggle button.active { background: #111111; color: #fff; }
}