How to rotate/snap 2D objects together based upon normal vectors

Question

Given some 2D objects with corresponding normal vectors I'd like to snap them together such that their normal vectors become opposites. So it'd look something like the following:

Unfortunately I can't get them to stick from all rotations/orientations and am not sure what I'm doing wrong. Hopefully someone can help out. Here's the malfunctioning code:

var my_ang = cnct_joints.mine.normal_angle + cnct_joints.mine.get_global_rotd()
var their_ang = cnct_joints.theirs.normal_angle + cnct_joints.theirs.get_global_rotd()
my_ang -= 180 if abs(round(my_ang)) >= 180 else 0
their_ang -= 180 if abs(round(their_ang)) >= 180 else 0

var diff = my_ang - their_ang
var diff_sign = 1 if my_ang < their_ang else -1
diff -= 180 if abs(round(diff)) >= 180 else 0

set_global_rotd(get_global_rotd() + diff_sign * diff)

Answer 1

I had to change the joint's normal_angle to a normal vector. But this seems to be working! Only took a week or more to figure out...

var start = cnct_joints.mine.normal
var end = -cnct_joints.theirs.normal.rotated(cnct_joints.theirs.get_global_rot())
var ang = start.angle_to(end)
set_global_rot(ang)