body { font-family: system-ui, Arial, sans-serif; margin: 0; }
header, main, footer { max-width: 900px; margin: auto; padding: 16px; }
form { border: 1px solid #ddd; padding: 16px; margin-top: 24px; }
input, button { width: 100%; padding: 10px; margin-top: 8px; }
button { background: #2563eb; color: #fff; border: none; }