Try modify your code like the followings :

Code:

---

function photonBeam()
{
   	my.skill_a = -random(5); // any number
	my.skill_b = 0; 
	my.skill_c = 0;

	vec_rotate(my.skill_a,you.pan);
 	vec_add(my.vel_x, my.skill_a);
 	
	my.move = on;
        my.size...
        my.bright...
        my.beam...
        .......
        .......
}  

vec_for_vertex(vert1,me,455);
//vec_rotate(vert1,my.pan);
vec_for_vertex(vert2,me,509);
//vec_rotate(vert2,my.pan);
effect(photonBeam,1,vert1,velocity);
effect(photonBeam,1,vert2,velocity);

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