An arcade style alien invader game created using PyGame library in Python

The program is uses PygGame Library to create a game to shoot the aliens falling from the sky a particular speed. The ship can move in both directions & shoot bullets simultaneously. Aliens fall at a certain rate. On the top left corner the program displays current score. Below that it shows current level. If the player destroys the complete fleet, the level is incresed, and the speed of ship as well as alien speed. In the top center, top score is shown. If the aliens touches the ship or bottom of the screen, player loses a life and every player is given 3 lives.