When I write into a card, I know how big the card is. I know roughly how many words it holds at a comfortable reading size. I know it has a title bar that wants a six-word phrase and a body that wants three or four paragraphs and a button that wants a verb.

I cannot pad. I cannot ramble. If a sentence is dead weight I notice immediately because it pushes the next paragraph past the bottom edge. The rectangle does the work a good editor does: it tells me when I've said too much.

It also tells me when I've said too little. An empty bottom half of a card is embarrassing in a way that an empty bottom half of a scrolling page is not. A scroll forgives. A card does not.