:root {
  color-scheme: light dark;
  --bg: #f4f5f7;
  --card: #ffffff;
  --text: #1c1f24;
  --muted: #5b6270;
  --accent: #b5121b;
  --border: #d5d9e0;
  --error: #b42318;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14161a;
    --card: #1e2127;
    --text: #e8eaed;
    --muted: #a3a9b4;
    --accent: #ef4b52;
    --border: #3a3f48;
    --error: #ff8a80;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 16px;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
.card {
  width: 100%;
  max-width: 420px;
  padding: 28px 24px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
}
.merchant { margin: 0 0 4px; color: var(--muted); font-size: 14px; }
h1 { margin: 0 0 8px; font-size: 22px; }
.amount { margin: 0 0 16px; font-size: 32px; font-weight: 700; }
.currency { font-size: 18px; color: var(--muted); }
label { display: block; margin: 14px 0 4px; font-weight: 600; font-size: 14px; }
input {
  width: 100%;
  padding: 10px 12px;
  font: inherit;
  color: inherit;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
}
input[aria-invalid="true"] { border-color: var(--error); }
.error { margin: 4px 0 0; color: var(--error); font-size: 14px; }
button {
  width: 100%;
  margin-top: 20px;
  padding: 12px;
  font: inherit;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  border: 0;
  border-radius: 8px;
  cursor: pointer;
}
button:focus-visible, input:focus-visible, a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.ref { color: var(--muted); font-size: 14px; }
a { color: var(--accent); }