No behaviour change. The start mechanism is one expression, screen_view.gd:684:
var t := leaf_time_units if leaf_time_units >= 0.0 else time_units
leaf_time_units is set only by the --leaf-time diagnostic and is -1.0 on every
real boot, so the sweep rides the title's own clock from 0 with no offset.
Refuted the obvious reading, which was mine before checking: ptloop01/02 declare
0:0 70:0 100:255, so the parents LOOK like the gate. They are not -- the leaf is
what reaches the screen and the parent's alpha is decoded as not multiplied in.
pteff03's leaf declares 0:255 and is travelling from t=0; the plate arrives at
t=214-236, so the port starts the sweep ~150 units (~2.5 s) early, which is the
size and direction the human reported.
A start time is an OFFSET and leaf_time_units is an ABSOLUTE override; the
one-line edit is a subtraction at 684 fed by one authored value.
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