:root { color-scheme: light dark; }
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  line-height: 1.5;
}
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px 16px;
}
.header { margin-bottom: 24px; }
.card {
  border: 1px solid rgba(127,127,127,.35);
  border-radius: 14px;
  padding: 18px;
}
.muted { opacity: .75; }
button {
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid rgba(127,127,127,.4);
  background: transparent;
  cursor: pointer;
}
.footer { margin-top: 28px; }