body { font-family: system-ui, sans-serif; margin: 0; }
main { padding: 24px; max-width: 720px; margin: 0 auto; }
.keys { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
button { padding: 8px 12px; border: 1px solid #ddd; border-radius: 8px; background:#fff; cursor:pointer; }
.result { margin-top: 16px; font-size: 20px; }