seperate gui from core
some bug fixes
add 'state' attribute
add basic functions to predict enemy moves
add 'stay_hidden()' and functions it uses
add shooting methods
add spawning walls in update method
input getting including pygame
now behaviors return sets of instructions
start breaking down the 'update' method
minor changes
improved readability
organise imports
add x, y properties
improve readability
fix bug ing get_flight_time