Loop playback — the transport repeating the open symbol — is editor state and
the document has never heard of it. A looping INSTANCE is a node repeating the
symbol it places, which is the four-frame tire turning for the hundred and
twenty frames it is on screen, and it lives in the document as
`:playback {:end :loop}`. Same word, two scopes; named apart here before
anything is built on either.
The status of the second one is the surprise: it already works and cannot be
asked for. `node/placed-frame` does the modulo, `node/problems` already admits
`:end :loop`, `audio-tracks` already expands the periods — and no control sets
it anywhere in the UI. So the tire is three pieces of work, not one: somewhere
to edit an instance's playback, a block that draws its repeats rather than
only its first pass as the timeline's own docstring admits it does, and the
audio period guard.
This also pins down when the held cel can be torn out. Turning every drawing
into a one-frame looping instance is only safe once a looping instance can be
seen and edited; otherwise every drawing in the document quietly acquires a
property with no control on it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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