:root {
  color-scheme: light dark;
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --accent: #4a6ff0;
  --line: color-mix(in oklab, currentColor 20%, transparent);
  --surface: color-mix(in oklab, canvas 92%, currentColor 8%);
}
* { box-sizing: border-box; }
body { margin: 0; padding: 16px; }
main { margin: 0 auto; max-width: 520px; }
h1 { font-size: 1.35rem; margin: 0 0 4px; }
#connection { margin: 0 0 16px; font-size: 0.85rem; opacity: 0.75; }
#calc-form { display: grid; gap: 8px; }
label { font-size: 0.85rem; opacity: 0.8; }
input {
  font: inherit; padding: 12px; border: 1px solid var(--line); border-radius: 10px;
  background: var(--surface); color: inherit; min-height: 44px;
}
#result {
  min-height: 44px; padding: 12px; border-radius: 10px; border: 1px dashed var(--line);
  font-variant-numeric: tabular-nums; overflow-wrap: anywhere;
}
button {
  font: inherit; min-height: 44px; padding: 10px 14px; border-radius: 10px;
  border: 1px solid var(--line); background: var(--surface); color: inherit; cursor: pointer;
}
button:hover { border-color: var(--accent); }
button:focus-visible, input:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
#submit { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
.keys { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 8px; margin-top: 16px; }
.keys button { font-variant-numeric: tabular-nums; }
#hint { font-size: 0.8rem; opacity: 0.72; margin-top: 16px; }
@media (max-width: 380px) { .keys { gap: 6px; } button { padding: 8px; } }