STARTER PACK
Sinclair User, October 1984


BASKETBALL

Improve your basketball skills with a program for the 1K ZX-81
by Paul Kecskemety of Cheshunt in Hertfordshire. The screen
displays a basketball net and you are represented by an inverse
'A' which moves from left to right. Press any key to throw the
ball at the net, and see how many you can score.

To save space, Paul has used character codes instead of ordinary
numbers. To find out what the codes represent, look at appendix A
in the ZX-81 manual.


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CIRCLE PATTERNS

CIRCLE PATTERNS draws up to sixty different patterns based on the
CIRCLE command, which is used here in an unusual way. The patterns
generated look very like tesselating floor tiles and could be used
to good effect in title screens.

The program was written for the 16K Spectrum by D Trebilcock of Sale
in Cheshire.

Program Explanation

Variables:
col     the number of the colour used
rad1    the radius of the inner circle
rad2    the radius of the outer circle
amend1  adjustment to the horizontal print position
amend2  adjustment to the vertical print position
dec     size factor for the pattern
c       control for FOR/NEXT loop
a,b     hold data for print positions

Line   20       Sets ink to black and the rest of the screen to white.
Line   30       Sets the colour for the pattern at random.
Line   40       RESTORE tells the computer to start READing data from
                a particular DATA statement - in this case at line 250.
                Without the RESTORE command, when the program was
                executed for a second time the computer would be unable
                to find any more data to load.
Lines  60-  70  Set two different figures for a radius of the circle. 
                Depending on the size of each unit in the pattern, there
                may be more than one circle in each unit.
Lines  80-  90  Set two separate figures for adjusting where each part 
                of the pattern is to be printed.
Line  100       Sets a factor for the size of the pattern units; 0, 1 or 2.
Line  110       The main loop of the program starts here. There are 23
                units to be drawn.
Line  120       READs the print positions from DATA statements starting
                at 250. When the first statement is used up the computer
                moves automatically to the next.
Line  130       If the unit size is 1 or 2 the computer draws a small 
                circle. Normally with CIRCLE the circle is a curved line.
                Here, because INK and PAPER colours are set the same, the
                whole character square through which the circle passes is
                set to one colour. This is a peculiarity of the Spectrum use
                of colour which for once has been turned to good advantage.
                Try changing either the INK or PAPER colours and see what
                happens.
Line  140       If the unit size is 0 or 1 the computer draws a larger 
                circle, some of which may obliterate parts of the earlier
                circle.
Line  150       INKEY$ checks to see if you are pressing the keyboard. In
                this case, if you press "S" the program will STOP.
Line  160       The loop returns to line 110 to draw another unit.
Line  170- 180  The computer pauses to display the finished pattern and
                then goes back to line 30 to set a new colour and draw a
                new pattern.
Line  250- 260  DATA statements which contain the co-ordinates for
                printing the pattern. The program will READ them two at
                a time and then adjust them slightly for more variety. See
                what happens if you alter a few of them.


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BOWLING GREEN

In Bowling Green by Miles Sampson of London for the 16K Spectrum
your bowl travels across the bottom of the green, and moves in
towards the jack when you press ENTER. Please read the instructions
for entering graphics on the first page of the Program Printout
section before typing in the program.


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ALPHABET INVADERS

The aliens are sending us letters, which makes a change from guided
missiles. Earth's reactions have not changed, however - you still
have to shoot them down. Instead of using one key to fire, in
Alphabet Invaders you must press the key corresponding to the letter
you see on the screen.

Alphabet Invaders was written by Adam Leonard of Mossley in
Lancashire, and runs on the ZX-81 in 1K.
