I found a bug/error I just wanted to report to you. Great job by the way I love the engine it is a really great example for what I am trying to do in my own rts. Here is the error and how to reproduce it.
ERROR inaction number 1of Alarm Event for alarm 0for object obj_projectile_clight:Error in code at line 21:if (point_distance(next_target.x, next_target.y, targetx, targety)<chain_range)^at position 41: Unknown variable x
Place 1 friendly "villi" and one enemy unit in a new room and cast any of the spells. The multi-target spells error out with the unknown variable x - I have not altered your code, but I believe the error is because there is no next target.
Again thank you for making this it is really great.
Thanks for reporting that, I'm not really too worried about that since it's only suppose to be an example spell to show how one might go about making something similar. I'm sure you've already fixed it, but for those wondering how, just write "if instance_exists(next_target)" above that line (line 21) where the error occurred.