NEW YORK (16K Spectrum)
by P Watson
from Popular Computing Weekly (2 June 1983), pages 10-11

This program is called New York. It is basically an Invaders-type game for
the 16K ZX Spectrum.

First of all instructions are printed on the screen. Next, you input your
level of difficulty (best on level 8).

The program then plots some random stars and prints a New York skyline. Your
score and difficulty level are printed at the top left-hand corner.

Aliens now start descending from the top of the screen. If they get past
your flying disc they crush one skyscraper. If, however, they hit your disc
they self-destruct.

After 20 aliens have attacked, a mother-ship will pick up surviving aliens.
When the mother-ship returns to the left-hand side of the screen, the
computer plots some more random stars.

Then, the next attack wave starts. This process is repeated until you only
have three skyscrapers left. Then the game ends telling you that a
sufficient amount of New York has been destroyed.


LIST OF VARIABLES

sc = The score, 1 is added to the score every time an alien is hit.
bh = The bat's height. The bat height moves one line further up the screen
after each attack wave.
aw = Determines which attack wave you are on.
k  = The x value of the alien.
c  = The number of aliens that have actually descended.
i  = How many skyscrapers have been demolished.
g  = A variable used for a 'for - next' loop when defining the graphics for
     the skyscrapers.
m  = How many stars you get.
u  = Height of the buildings.
z  = The y value of the buildings.
x  = The height of your bat.
y  = The distance across the screen of your bat.
l  = The y value of the alien.
f  = The 'for - next' loop which enables the aliens to descend.
le = The level of difficulty which you input at the start of a game.
v  = A 'for - next' loop which replaces a pause statement. This is because
     pause statements can be interrupted.
w  = The x co-ordinate of the mother-ship when it is picking up the aliens.
q  = The y co-ordinate of the mother-ship when it is picking up the aliens.
r  = The y co-ordinate of the alien as it ascends to the mother-ship.
h  = The y co-ordinate of the mother-ship when it is returning to the
     left-hand side of the screen.
b  = The variable used in the graphics effect at the end.