Created "boid_number" so the "raw numbers" in the code could be removed.
Created x_pos_range for the x position range and did the same for y (and the x and y velocities). This was done to remove the raw numbers from the code.
Replaced xs, xvs etc with x_pos, x_vel so it's more obvious what these quantities actually are.
Created config.yml and taken all of the constants defined in the code and placed them in there.
Added raw numbers from boids.py to the config.yml.
Created a fly_towards_middle function to replace the section in the update_boids function.
Created fly_away_from_middle function which simplies part of the update boids function