:root {
  --bg: #ffffff;
  --fg: #1f2933;
  --muted: #5f6b7a;
  --line: #e3e7ec;
  --accent: #4f46e5;
  --card: #f7f8fa;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0f17;
    --fg: #e6e9ef;
    --muted: #9aa4b2;
    --line: #232a36;
    --accent: #8b85ff;
    --card: #121826;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

header, main, footer {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 16px;
}

header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 16px;
  padding-top: 24px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
}

.brand { font-weight: 700; font-size: 18px; color: var(--fg); text-decoration: none; }
nav a { color: var(--muted); text-decoration: none; margin-left: 16px; font-size: 14px; }
nav a:first-child { margin-left: 0; }
nav a[aria-current="page"], nav a:hover { color: var(--accent); }

main { padding-top: 32px; padding-bottom: 48px; }
h1 { font-size: 30px; line-height: 1.2; margin: 0 0 8px; }
h2 { font-size: 19px; margin: 32px 0 8px; }
p, li { color: var(--fg); }
.meta { color: var(--muted); font-size: 14px; margin-bottom: 24px; }
a { color: var(--accent); }
ul { padding-left: 22px; }
li { margin: 4px 0; }

.callout {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px 18px;
  margin: 16px 0;
}

form.sample {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 20px;
  margin: 20px 0;
}

.sample-tag {
  display: inline-block;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  margin-bottom: 12px;
}

label.field { display: block; font-size: 14px; font-weight: 600; margin: 12px 0 4px; }
input[type="text"], input[type="tel"], input[type="email"] {
  width: 100%;
  padding: 10px 12px;
  font: inherit;
  color: var(--fg);
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.consent {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  margin: 18px 0;
  font-size: 14px;
}
.consent input { margin-top: 4px; width: 18px; height: 18px; flex: none; }

button {
  font: inherit;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  border: 0;
  border-radius: 8px;
  padding: 10px 18px;
  cursor: pointer;
}
button:disabled { opacity: 0.5; cursor: not-allowed; }
#sample-result { margin-top: 12px; font-size: 14px; color: var(--muted); }

footer {
  border-top: 1px solid var(--line);
  padding-top: 16px;
  padding-bottom: 32px;
  color: var(--muted);
  font-size: 13px;
}

.cards { display: grid; gap: 12px; margin: 24px 0; }
@media (min-width: 640px) { .cards { grid-template-columns: repeat(3, 1fr); } }
.card {
  display: block;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px;
  color: var(--fg);
  text-decoration: none;
}
.card:hover { border-color: var(--accent); }
.card strong { display: block; margin-bottom: 4px; color: var(--accent); }
.card span { font-size: 14px; color: var(--muted); }