Prompt it

Create a beginner-friendly responsive newsletter signup using semantic section, heading, labelled email input, submit button, and helper text. Keep every custom selector under .cf-newsletter and ensure every selector is represented in the supplied HTML so live CSS edits visibly update the preview. Use a real email type, autocomplete hint, required validation, readable contrast, 44px touch targets, visible keyboard focus, responsive stacking from 320px, and reduced-motion handling. Do not use JavaScript, external assets, framework classes, or unlabeled inputs. Return complete copy-ready HTML and dependency-free CSS, then explain the form labelling and responsive decisions.