Splash Potion Delivery

Rules

Range	Targets up to 4 blocks to the side and 2 blocks above or below the impact are checked. The gap between the potion and the target must be under 4 blocks.
Measuring distance	The gap is measured between the hitboxes of the potion and the target. The target's hitbox counts as up to 0.3 blocks larger; this extra grows from 0 to 0.3 between the potion's 2nd and 8th tick of flight.
Strength	Strength = 1 - gap ÷ 4. Touching hitboxes give full strength, a gap of 2 blocks gives half.
Timed effects	Duration is the potion's duration × strength, rounded to the nearest tick. A result of 1 second (20 ticks) or less is not applied.
Effect level	Distance changes duration and instant amounts, never the effect level.
Instant effects	Instant Health and Instant Damage are multiplied by strength and rounded to a whole point. At full strength that is 4 health points or 6 damage at level I.
Undead mobs	On undead mobs the two are swapped: Instant Health deals damage and Instant Damage heals.