INTRODUCTION:

In Alien Invasion, the player controls a ship that appears at the bottom center of the screen. The player can move the ship right and left using the arrow keys and shoot bullets using the spacebar. When the game begins, a fleet of aliens fills the sky and moves across and down the screen. 

The player shoots and destroys the aliens. If the player shoots all the aliens, a new fleet appears that moves faster than the previous fleet. If any alien hits the player’s ship or reaches the bottom of the screen, the player loses a ship. If the player loses three ships, the game ends.

MODULES:

A. Main: 

Contains the code to execute the game and all of its modules.

B. Settings:

The "settings.py" module, containing a Settings class, was  created to store all of our settings which can be invoked throughout the length of the main code. 

C. Ships:

The "ship.py" module contains the class Ship. Here the ship is loaded and positioned into the main program. The ship's movement is also controlled at this end.

D. Game Functions:

The "game_functions.py" module contains all of the functions which will control the movement, firing and other actions of the ship.

E. Aliens:

Contains all of the functions used to define the alien class, control their movement etc.

F. Bullets:

Contains functions used to define bullet characteristics.

G. Game Stats:

Scoring, difficulty levels, player lives etc.