Don't know if anyone posted something like this yet, but here goes...
Here's a few facts about SoO's chain lightning.
-Chain lightning does 60 unmodified hack damage. Unlike most other units, the 60 damage is per strike and not per second.
-SoO has a range of 18, meaning the initial bolt can hit a target at that range. The successive bolts make it possible for SoO's chain lightning to hit a target beyond the 18 range.
-After the initial bolt, a maximum of 4 successive bolts can strike.
Now here are some small observations:
1) While the initial bolt has a maximum range of 18, the successive bolts do not. Check out [Figure 1]. The first sentry tower is located exactly at the SoO's max range. The distance from tower 1 to tower 2 is obviously much less than the distance from SoO to tower 1.[Figure 1]
2) This concerns the algorithm for how the successive bolts choose their targets. First of all, it is not random. When attacking targets, the lightning will always take the same target path as long as both SoO and the targets remain stationary. It seems as though the successive bolts' priority when choosing additional targets is direction rather than distance. Notice on [Figure 2] how the towers above and below the tower struck by the initial bolt are closer than the one on the far right? Yet the tower on the far right is struck by the 2nd bolt, and the other towers are ignored. Also notice that the direction from the inital target to the tower on the far right is roughly the same as the direction from SoO to the initial target.[Figure 2]
[Figure 3]
Why does this matter? Look at [Figure 3]. It is the exact same setup as in [Figure 2] except SoO is positioned differently. Look how many targets are hit from this angle. Another little theory of mine is there is a maximum angle that is taken into consideration. What I mean is even if successive targets are in range, but at quite obtuse angles, then they will not be considered for targetting of successive bolts. That is why a bolt strikes from the bottom-most tower to the right-most tower in [Figure 3], but a bolt does come back and strike from the right-most tower to the bottom-most in [Figure 2]. They are exactly the same setup and the distance is exactly the same as well, but in [Figure 1] the angle is much more obtuse.3) If two targets are at equal angles with respect to the last bolt, the closer one is chosen.
[Figure 4]
4) Can SoO’s lightning hit from ground units/buildings to air units and vice-versa?
Yup. Check out [Figure 5]. How does the flying unit affect the target path now? I don’t believe it does any differently from ground-to-ground, because air units have a respective ground position (to see what I mean try placing down a flying unit in the editor).[Figure 5]