Initialize the game: Set black background with stars randomly
distributed, load game sounds and spaceship and alien images,
initialize game object locations as they will appear on screen.
Handles a space bar press as an attempt to shoot a laser and
shoots a laser only if fewer than the maximum number allowed are
on screen; play shooting sound if shot was made.
Advances star straight downward 1 pixel per move, restarting
the screen position to the top of the screen when the star
moves off the bottom of the screen.
Overrides update to eliminate clearing of the graphics
context before each screen paint in order to avoid
annoying flicker and clears the screen when a flag is set.
W
width -
Static variable in class SpaceInvaders.Alien
width of Alien image
width -
Static variable in class SpaceInvaders.Ship