:root {
  color-scheme: light dark;
  --bg: #f6f6f4; --card: #fff; --fg: #1c1c1e; --muted: #6b6b70; --border: #d0d0d5;
  --accent: #2f6fed; --accent-fg: #fff; --error-bg: #fde8e8; --error-fg: #a11919;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #131315; --card: #1e1e21; --fg: #ececee; --muted: #9a9aa2; --border: #3a3a40;
    --accent: #5b8df5; --accent-fg: #0b0b0c; --error-bg: #4a1d1d; --error-fg: #ffb4b4;
  }
}
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0; display: grid; place-items: center; padding: 16px;
  font: 16px/1.4 system-ui, sans-serif; background: var(--bg); color: var(--fg);
}
main {
  width: 100%; max-width: 360px; padding: 24px;
  background: var(--card); border: 1px solid var(--border); border-radius: 16px;
}
h1 { margin: 0 0 16px; font-size: 24px; }
form { display: grid; gap: 16px; }
label { display: grid; gap: 6px; font-size: 14px; color: var(--muted); }
/* 16px+ so mobile browsers do not zoom into the field; 48px tall tap targets */
input, button { font: inherit; font-size: 17px; min-height: 48px; border-radius: 10px; }
input { width: 100%; padding: 10px 12px; color: var(--fg); background: var(--bg); border: 1px solid var(--border); }
input:focus-visible, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
button { border: 0; font-weight: 600; color: var(--accent-fg); background: var(--accent); cursor: pointer; }
.error { margin: 0 0 16px; padding: 10px 12px; border-radius: 10px; background: var(--error-bg); color: var(--error-fg); }