Gnashers - Michael Scott & Gavin Monk (Your Spectrum-Issue 1-Page 91)


Gnashers are a rather rare breed of gremlin whose main source
of sustenance seems to be the dam which holds back the water
from flooding a nearby town. But the local townspeople think
nothing of a wave of hungry Gnashers swooping overhead,
making their way to the dam to take out another massive bite.
	Their confidence comes from the fact that there is a crack
squadron of bombers that has so far managed to quell the threat
of the Gnashers. That is, until you took charge of the planes!
You control the plane under automatic pilot by pressing the L
key, and to drop a bomb on some unsuspecting Gnasher you
simply press the B key. Take care when releasing your deadly
missile - the Gnashers fly at much lower levels than your
plane's trajectory, so you have to judge very carefully when to
drop the bomb so that it collides head-on with the Gnasher.
	When you start the game, the task is relatively simple in that
the dam comprises three barriers, all of which must be eaten
through before the water comes cascading through. However,
once you have killed 11 of the Gnashers, the game gets a little
more difficult in that the dam now has only two barriers. Again,
when you have killed 11 hungry gremlins, you start all over
again - this time with the dam made up of only one barrier.
Now you've got to keep on your toes because even if you let just
one Gnasher through it'll mean that ... glub, glub, glub ...


Lines 1-170     Draw the town and the dam. The variable, ts (top score), is
		initially set to zero. l$ is a flag which indicates if the plane
		is flying. Line 70 draws the water behind the dam, and lines
		80-110 draw the dam to the required thickness, denoted by
		the variable, dt. The last row of the dam is drawn in inverse
		video so that a flood can be checked tor later using the
		attribute function. Lines 120-170 draw the town and the
		ground. Finally, line 125 checks to see it you are on the last
		level of the game and, if so, sets dt equal to ten - to be
		used as a flag later in the program.
Line 180        Prints the score and the current high score.
Lines 269-400   Move the Gnashers. qq is a flag to check that only one
		bomb is on the screen at any one time. bb is the flag holding
		the vertical position of a Gnasher, and cc is used to hold the
		horizontal position, b1 is the attribute of the Gnasher's
		position. Lines 300-320, 370 and 385 print and remove the
		Gnasher once it has been bombed successfully. Line 340
		checks to see if a Gnasher has managed to eat its way
		through to the last barrier of the dam. Line 350 checks to
		see if a Gnasher has reached the dam. Line 375 checks to
		see if the L key has been pressed and, if it has, moves the
		program to the 'plane' routine.
Lines 409-480   Control the movement of the plane; line 420 is actually the
		line responsible for the movement of the plane. b$ and pp
		are two flags which, respectively, check to see if a bomb
		has been released and whether this is your first call to the
		bomb routine.
Lines 489-520   This section of the program moves the bomb, where zz is
		used as the flag holding the horizontal position of the bomb.
		Line 495 actually prints the bomb. Line 500 checks if the
		bomb has hit a Gnasher and if so, increments your score,
		sets the flags and returns. If you should miss the Gnasher
		and hit the town instead, your score is decremented via line
		510, the flags are set and the program returns.
Linen 539-560   If a Gnasher should eat its way through the dam barrier,
		this section of code will make the water level behind the
		dam become lower and draw the water submerging the town.
Lines 570-640   The end of game routine. A tune is played to signify that the
		game is over and you will be shown your score alongside
		the current top score.
Lines 680-740   This routine increments the score and prints it on the screen
		if you have managed to get more than 100 points.
Lines 760-970   This routine checks if the instructions for the game are
		required by the user. If not, the program moves on the user-
		defined graphics routine.
Lines 999-1560  This area of the program sets up the user-defined graphics
		needed in the game.
Lines 2000-3010 This routine plays a tune while waiting for the various keys
		to be pressed at the beginning of the program.

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TYPE: Arcade 

COMMENT: 


This info file was typed by Jim Grimwood

Downloaded from:
Desert Island Disks -- http://www.image.dk/~frankie/
Maintained by:
Michael Bruhn -- frankie@image.dk

