I made a few minor tweaks.

1) The EnemyShotEntity class had hard coded constants defined for the invader shot size. I made these constant variables.

2) I defined the invader shot constants in the SIConstants class.

3) I added a note to the SquareInvaders class. If one want to make the invader shots the same color as the invader firing the shot, they can uncomment the line below in the method userGameUpdateEntity method.

enemyShot.setColor(currentEnemy.getColor());