In short :
[Spoiler ahead]
> you gain point by repairing the tomb stone which have three state : OK (grey) ; bad (dark grey); broken (almost invisible).
> If a broken one isn't repaired by the next wave, you loose 10 points
> When your light touch one it goes to OK, except sometimes where you have directly touch them
> Green souls give you a bonus of points AND light length so you must prioritize getting them
> I'm not sure but i feel like boosting makes you loose bonus or points
There is some more to say but you should get to a decent score with this !