ADVENTURE-X (aka ALIEN CITY)
by Steve Craddock
for ZX Spectrum 48K
published in "Big K", issue #2 (May 1984)

Returning to Earth from Alpha Centauri, your teleport beam is interrupted
by a weird glitch and you find yourself stranded in an eerie, apparently
deserted alien city. As you begin to investigate your surroundings you
encounter a friendly android by [the] name of Eddie. With his help you
begin to explore a maze or rooms, encountering oddly familiar objects and
diabolical dangers at every turn. Will you ever find a way to leave this
alien world? Or will you be stranded forever in an endless labyrinth -
where perhaps you are not alone...?


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H-Bloc
By Antony Trenker, Published in Big K, May 1984

   A fiendishly cunning strategy game for 2-4 players. Grab your bricks
as they come down the chute and out-build your opponents by hemming them
in. Last one in plays Yosser Hughes ... can you do this job?

   You must simply surround another players brick with your own. If
there is a space or a wall on one side the player cannot be surrounded.
He will only die if he is surrounded by four other bricks. You can also
surround yourself, so beware! 

   You can play safe by putting your bricks near the edge of the walls
or form a ring of bricks with a space in the centre. The four in the
ring cant be surrounded but can surround others. 

You can play a risky game by luring other players into squares which
they think will surround you but actually surround them.

Use the cursor keys 5,6,7 & 8 to move your brick. Press 0 to place
the brick. Press s to stop or end the game.


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PLOTTING TO SUCCEED
from BIG K No.2 May 1984

Many computer games depend entirely on good graphics for playability.
In addition graphics pure and simple are emerging as the fastest devel-
oping form of computer art.In this first of an occasional tutorial
series, RICHARD TAYLOR - designer CRL's ZX81 High Resolution and more
recently, the Fifth games-writing extension to Sinclair BASIC - explains
some routines both ancient and modern on the Sinclair Spectrum.

The computer on which this article concentrates is the ZX Spectrum.
Programs listed here are, except Listing 8, short and simple and lend
themselves well to conversion to other machines. The rest will work
equally well on 16K and 48K machines.

Sinclair BASIC has a rather limited vocabulary of graphic commands -
namely PRINT, PLOT, DRAW and CIRCLE. Matters are not helped by the
relatively sluggish speed of Sinclair BASIC which makes movement and
animation difficult - and nigh impossible if you intend to animate more
than a couple of object simultaneously.

The only real solution to this fundamental problem is to write programs
in machine code for the sake of speed. Another possible alternative is
to use a faster language, such as FORTH or PASCAL, or to use an extended
version of BASIC that is specifically designed to handle animation and
movement.

Static

For these reasons I'll concentrate mainly on static displays rather than
their animated counterparts. The four commands and the numerous math-
ematical and graphical functions of Sinclair BASIC represent about the
minimum requirement to produce anything worthy of a machine like the
Spectrum. A surprisingly small ammount of BASIC can often produce quite
stunning displays.

Listing 1 illustrates this rather nicely. This six line BASIC program
produces a finely detailed regular pattern which looks quite attractive
even without the use of colour. The basis of the program is the drawing
of lines in OVER 1 mode. As you will (naturally) recall from chapter 17
of the BASIC manual, OVER alters the behaviour of the graphics commands.
Instead of just plotting a pin-point by making it the ink colour,
irrespective of the pixel's previous state, OVER 1 changes this so that
a pixel is set to the ink colour if it was previously the paper colour
and the other way about.

Exellent

The use of OVER 1 can produce some quite excellent effects, especially
if many lines are drawn in close proximity to one another.

Listing two produces a similar sort of pattern but it is circular,
rather than the less inspiring rectangular shape. The pattern is
created by the effects of lines radiating from the centre of the circle
to it's circumference, at a one-degree spacing; 360 lines in all. The
white area around the centre of the circle is caused by the numerous
lines originating from the centre interacting with one another to leave,
in the main, just the white paper colour. The whitish areas around the
edges of the circle is caused by the gaps between the lines drawn from
the centre.

A useful advantage of DRAW is the ability to produce curved lines
between two points. Listing 3 provides an example of this. You might
notice a slight pause preceding the drawing of each curved line. This
represents the time used by the computer while it is 'number crunching'
in order to work out what the line mathematically looks like; something
the computer has to do before it can actually draw the line.

Rosette

Listing 4 produces a sort of rosette shape. The program's slowish speed
is a result of the large ammount of mathematics that has to be done to
produce the shape, especially calculations involving SIN and COS which
are not particularly quick executing functions at the best of times.
Listing 5 produces a detailed spiral pattern. Again the large usage of
the SIN and COS functions slow down the program considerably.

In both listings 4 and 5 the expressions PEEK 23677 and PEEK 23678 are
used. PEEK 23677 simply returns the current x coordinate and PEEK 23678
returns the current y coordinate. These x and y coordinates detail the
point from which the DRAW command will draw a line. If you are convert-
ing the programs to another machine then you will have to replace these
expressions with an equivalent.

The sixth listing is a program which enables you to draw regular
polygons - shapes bounded by straight lines of equal length. When RUN,
the program will prompt you for the number of sides the polygon should
have. Numbers greater than about 20 result in  polygons with such short
lines that the shape looks more like a circle than a polygon.

Listing 7 also constructs a polygon but this time each point at the end
of a line is joined to every point at the end of a line to produce a
suprisingly detailed and intricate pattern. This pattern can be altered
by having polygons with different numbers of sides. Be careful in your
selections however as polygons with less than about 5 sides result in
simple and uninteresting patterns.

Expanding

Computer graphics is a very wide subject that seems to be rapidly
expanding all the time as new uses for graphics are found and new
techniques for producing them are discovered. The Spectrum is hardly
in the computer graphics league table but, nevertheless, it is capable
of some quite advanced and sophisticated work.

Next month:ATARI

note:I've ommited the sections refering to listing 8. When I get round
to typing this in, I will send a revised version of this text.
