Space Invaders Salma

Space Invaders is a two-dimensional fixed shooter game in which the player controls laser cannon by moving it horizontally across the bottom of the screen and firing at descending aliens.
The aim is to defeat five rows of eleven aliens that move horizontally right and left across the screen as they advance towards the bottom of the screen. The player defeats an alien, and earns points, by shooting it with the laser cannon. As more aliens are defeated, the aliens' movement and the game's music both speed up.
A special "mystery ship" will occasionally move across the top of the screen and award bonus points if destroyed. Several stationary defence bunkers partially protect the laser canon, but a numerous amount of blasts from the aliens or the player gradually destroy them.
Defeating aliens will occasionally award bonus points, extra hearts, or a powerful canon. These gifts can descend from a defeated alien; however, the player’s laser canon must touch the gift in order for the player to get it.
Defeating aliens bring another wave that is more difficult as it will be faster, a loop that can continue without end. The aliens attempt to destroy the cannon by firing at it while they approach the bottom of the screen. If they reach the bottom, the alien’s invasion is successful and the game ends. The game ends also when the aliens destroy the canon.
Therefore, this game depends on the speed of the player in defeating aliens before in addition to his intelligence in putting a strategy for winning.