:root {
  color-scheme: light dark;
  --bg: #f5f7fb;
  --surface: #ffffff;
  --text: #172033;
  --muted: #5d6678;
  --line: #dfe4ec;
  --accent: #1769e0;
  --accent-soft: #e9f1ff;
  --max-width: 760px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Yu Gothic", sans-serif;
  line-height: 1.75;
}

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

.site-header {
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 92%, transparent);
}

.nav {
  width: min(calc(100% - 32px), var(--max-width));
  margin: 0 auto;
  padding: 14px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  color: var(--text);
  font-weight: 700;
  text-decoration: none;
}

.nav-links { display: flex; gap: 16px; }
.nav-links a { font-size: 14px; text-decoration: none; }

main {
  width: min(calc(100% - 32px), var(--max-width));
  margin: 40px auto 64px;
}

.hero { margin-bottom: 28px; }
.hero h1 { margin: 0 0 8px; font-size: clamp(30px, 7vw, 44px); line-height: 1.25; }
.hero p { margin: 0; color: var(--muted); }

.card {
  margin: 16px 0;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--surface);
  box-shadow: 0 8px 30px rgb(30 50 90 / 6%);
}

h2 { margin: 0 0 12px; font-size: 21px; }
h3 { margin: 24px 0 6px; font-size: 17px; }
p, ul { margin-top: 8px; }
ul { padding-left: 1.4em; }
.meta, .note { color: var(--muted); font-size: 14px; }
.note { padding: 14px 16px; border-radius: 10px; background: var(--accent-soft); }

.button {
  display: inline-block;
  padding: 10px 16px;
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font-weight: 650;
  text-decoration: none;
}

footer {
  width: min(calc(100% - 32px), var(--max-width));
  margin: 0 auto;
  padding: 24px 0 40px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1420;
    --surface: #171e2c;
    --text: #f3f6fb;
    --muted: #aeb7c7;
    --line: #2b3548;
    --accent: #6da8ff;
    --accent-soft: #1a3152;
  }
  .button { color: #08111f; }
}