BATTLE STATIONS
by Robert Higgins
from Personal Computer News weekly, 17th March 1984

This Spectrum game from Robert Higgins of Stoke Poges in Bucks takes
you back to the '40s. You take the position of a pilot in the NAF
(National Air Force). Unfortunately, due to your terrible luck and
awful flying skills, you have been demoted to the lowest possible rank
and given the task of manning the Anti-Aircraft guns.

Your only hope of achieving your lost rank and status is to shoot down
as many enemy aircraft as possible. To help in this task you are put
in charge of the new computer-assisted sighting system (code name
Blackcurrent).

Using your intimate knowledge of computers you are able to tinker with
the program by: a) increasing 10 in line 2010 to allow you more time;
and b) decrease (or increase) the 'diff' in lines 6 and 9003. These
hints should allow you to reach your goal (the officers mess) in time
for dinner.


3         Gosub and define the graphics characters.
4         Gosub and print introduction and instructions.
5-9       Set up variables and screen colours.
10        Gosub to draw runway and airfield.
100-125   Delete the sight using x and y as the horizontal and
          vertical positions.
130-165   Scan the keyboard and update the sight coordinates
          accordingly.
180-190   Delete the enemy aircraft.
195-230   Redraw the sight using UDGs (User Defined Graphics)
240-241   Fire the Ack-Ack guns and check for a hit.
242       Check ammo; if there is none left then go to routine for end
          of game.
245-247   Get a new random position for the enemy aircraft and check it.
248       Make aircraft movement sound.
250       Update the horizontal position of the aircraft by the
          difficulty.
260       Check whether the aircraft has flown past; if so the next plane.
300-305   Print the aircraft onto the screen.
310-315   Update the screen information such as score, number of
          waves, etc.
999       Continue the game.
1000-1040 Enemy plane hit, explosion routine. In line 1000 the two
          graphics characters at the end of the line are code 137 and
          134. The characters at the end of 1010 are 134 and 137.
1050      Select new start position for approaching enemy.
1060-1070 Update the score according to how close the hit was.
1073      Get some more ammo.
1074      Update and check the number of shots fired.
1075-1080 Reset the border colour then return.
2000-2020 Plane has flown past check for ten planes.
4000-4999 Print the scenario and instructions.
5000-5200 Set up the user defined graphics.
7006      Post mortem on your performance.
7007-7015 End of game beeps.
7020-7065 Set the aerodrome on fire.
7070-7075 Oh dear! you have failed.
7084-7092 Work out the rank to be awarded.
7093      Print rank.
7094-7097 If high score then get and print name.
7098-7999 Prompt for another game then reset variables and replay.
8000-8999 Draw the aerodrome. Note that the spaces in line 8050 are
          inverse spaces.
9000-9020 Jolly good, you've completed a wave; set up the variables
          for next.