Eu gostei bastante do jogo, sinceramente eu não teria o que mudar. e com toda certeza vou passar um dias lendo o seu codigo para entender um monte de coisas.
infelizmente não consegui lutar com o boss final por conta de algum erro no codigo.
apareceu isso no final:
############################################################################################
ERROR in action number 1
of Step Event0 for object obj_boss:
Variable <unknown_object>.item_num(100273, -2147483648) not set before reading it.
at gml_Object_obj_boss_Step_0
############################################################################################
gml_Object_obj_boss_Step_0 (line -1)