A 2D game built using Pygame package in Python
- When the game begins, a fleet of aliens move across and down the screen.
- The goal is to destroy all of them.
- The player controls a rocket ship using arrow keys, that appears at the bottom center of the screen.
- Shoot bullets with spacebar.
- If all the aliens are shot dead, a new fleet appears, with increased difficulty.
- If any alien reaches to bottom, player lose a ship.
- After losing three ships, the game ends.