Hello everyone...
According to feedback I added few features and improvements to the game. These are listed below:
1- The game asks for player name at the beginning so that it is used in storing player's high score.
2- added different types of backgrounds to give variety to the game.
3- the shield now is rendered as a force field around the ship to help the player identify how dangerous this situation is.
4- added homing missile weapon.
5- added ground units that attacks the player.
6- added few other stages.
7- fixed few bugs.
thanks again for all of you and have fun ːsteamhappyː