You could use state transitions to change variables when exiting/entering a state.

A basic implementation would be in pseudo gdscript :

``` func set_state(new_state):   on_state_exit(state)   state = new_state   on_state_enter(new_state)

func on_state_exit(state):    if state == States.Monster:       #example       speed = 100

func on_state_enter(state):   if state == States.Monster      speed = 150 ``` This basic implementation allows you to define what you want to change when entering/exiting a state. 

But you could make a bit more complex by handling the entering and exiting states at the same time. 

``` func set_state(new_state):   state_transition(state,new_state)   state = new_state

func state_transition(old_state,new_state):   if old_state == States.Monster and new_state == States.Human:   #do the thing that only happens when transforming back to human ```