Penner's back overshoot s = 1.70158, the magnitude of the anticipation
dip in backIn / the settle overshoot in backOut.
The number is not arbitrary: 1.70158 is the value for which the classic
back curve overshoots by exactly 10 % of the range. It is pinned as a
constant rather than inlined so the three back variants cannot drift apart.
Penner's back overshoot
s = 1.70158, the magnitude of the anticipation dip in backIn / the settle overshoot in backOut.The number is not arbitrary:
1.70158is the value for which the classic back curve overshoots by exactly 10 % of the range. It is pinned as a constant rather than inlined so the three back variants cannot drift apart.