01

02

03

1. Step 1

   Track the section

   One data-sv-pin wrapper, one sticky child. The driver writes --sv-scene as you scroll.

2. Step 2

   Give each piece an index

   Shots and steps carry --i. Distance to the scene is one max(). That is the crossfade.

3. Step 3

   Ship it

   No observers per step, no timeline library. Three scenes here; make it thirty.