An editor that disappears while you write, and is there when it matters.

You type, Letter stays out of sight. It checks spelling and grammar quietly in the background, in German, English, French and Spanish, even offline. Type “vier hoch zwei mal drei” and it writes 4² × 3 and works out 48 as you go. Math mode understands German.

And when a text must not end up in the wrong hands, you send it as a .letter file: encrypted with a password, signed by you and marked, so that a leak can be traced back to its source.