Yeah you just use enemy instance variables not global variables. On enemy 1 you have health, speed etc. You could also have a phase variable on the enemy. Then in your code you set if phase is 1, set all the variables to this. If phase is 2, set all variables to this. It looks like you are setting the instance variable values to the value of a global variable, I would base the values on what the enemies are doing and what phase they are in. They will have a default and then anything after that can be based on phase.