Interesting game! Sadly it crashed for me.
I hope this helps.
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FATAL ERROR in
action number 1
of Step Event0
for object obj_enemyGun:
Variable obj_enemyGun.py(100011, -2147483648) not set before reading it.
at gml_Object_obj_enemyGun_Step_0
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stack frame is
gml_Object_obj_enemyGun_Step_0 (line -1)