Hitstun is now calculated with a linear formula (as it has been in every previous game)
In vanilla Ultimate, hitstun is logarithmically scaled with knockback, which means hitstun per unit of knockback drops off as knockback increases. This has been reverted to that hitstun scales linearly with knockback, so higher percents should have more hitstun without affecting low percents
As a consequence, balloon knockback is no longer present. This was inherently tied to how hitstun was calculated, and we would rather have hitstun that works correctly that does not drop off at mid to high percents than keep balloon knockback
Most hitboxes that are either behind a character's base position or collide with an opponent that is behind said position will have their knockback angle flipped horizontally