Prose, paragraphs, and markers

Prose is any bare paragraph: no keyword, just sentences. In a create block the first bare paragraph after the blank line is the entity's description, and consecutive bare paragraphs append to it as separate paragraphs.

create the Reading Nook
  a room

  A stone bench curves around a sundial{weather}. Ivy softens
  every wall.

  Someone has left a folded blanket at one end of the bench.

Within a paragraph, line breaks are yours to place: lines join with single spaces when the text is rendered, so you can wrap prose at any width. A blank line is a real paragraph break.

A marker like {weather} splices generated text into prose at that spot. Every bare lowercase marker must name something the story declares: a phrase or a text hatch. Here weather is a cycling phrase, so the sundial reads differently on different visits:

define phrase weather, cycling
  whose shadow lies crisp in the afternoon sun
or
  whose face dims as a cloud slides past
end phrase

One marker is built in: {br} forces a hard line break with no paragraph gap, for text whose line structure is the point. The name br is reserved; you cannot declare a phrase or hatch with it.

create the sundial plaque
  aka plaque
  scenery
  in the Reading Nook

  The engraving is worn but legible:{br}
  I COUNT ONLY SUNNY HOURS{br}
  EST. 1898

A lone " is ordinary prose punctuation, so dialogue can open in one paragraph and close in another without upsetting the lexer.