168L我引用下Nefarius的话:
This is actually pretty simple, missiles that have
LastCollide enabled will store the unit
they've previously collided with and prevent a second collision with
this unit to occur, until the missile hits something else.
In a hypothetical situation:
Fallen1 gets hit by Missile1
Missile1 stores the Id of Fallen1
Fallen1 is again hit by Missile1
Game checks stored Id, if it matches, no hit occurs
Fallen2 is hit by Missile1
Missile1 stores the Id of Fallen2
Fallen1 is again hit by Missile1
Hit occurs