In response to a request from the editor I present a
joystick version of the game Blockbreaker which was published in issue 20.
As a bonus, or maybe to frustrate those of you who can't get past level
2(!), I have also included an auto-play modification so you can see just
how the game should be played.
THE MISSING HIGH SCORE FEATURE
Before we begin, however, a correction to the original
program. Blockbreaker was written on a 32k Atari 400 and until very
recently I was unable to test it on the XL or XE. Unless you also use a
32k machine you will find that the high score feature is not displayed
between games. Fortunately the correction is a very simple one. Referring
to the original listing in Issue 20, line 155 should be modified by
changing the '120' in the fourth statement to 'PMB' as follows.
PLUG IN THAT JOYSTICK!
I did not include a joystick routine with the original
version because I felt that the use of a joystick made the game virtually
unplayable since it lacks the precision of the analogue input which a
paddle provides. I suppose, to some degree, it will depend on the
individual's dexterity and reaction time so I've listed the modified lines
below for you to try for yourself.
Type in the original program from Issue 20, or load it
if you have already typed it in, and then modify it as follows.
Change the following lines
Now add
The 29th DATA statement in line 1940 controls the sensitivity of the joystick. Change its value (4) to alter the speed of
your bat. Since it controls the delay loop, increasing its value will slow
down the bat.
The code in line 1940 causes the bat to move at a constant speed. I have
not experimented with an accelerating bat since I felt that this would
cause further frustrations during play but if anyone wishes to dabble with
the routine, ensure that your machine code fits into the listing between
lines 1930 and 1950 and that it ends with an RTS (I've used location 7 as
the delay variable).
SIT BACK AND WATCH
If you would like to see the game demonstrated then make
the following changes and additions to the original (i.e. paddle) version
of the game. Now sit back and watch Atari do all the work. Of course you
could always plug in a paddle and pretend you are a real champion!
Change the following lines
Now add
Blockbreaker will play forever in this mode (and introduce a minor bug at
the higher levels!) so you may like to make the Atari a bit more 'human'
by modifying the above version as follows.
Change these lines
The Auto routine is again situated between BASIC lines 1930 and 1950 and
machine code freaks will be able to decipher the routine given the
following information.
Location 1537 - the ball's (Player 2) vertical position
in the PMG table.
Location 1539 - the ball's horizontal position.
Location 1541 - the bat's (Player 0) horizontal position (left edge).
Location 7 - the 'random' variable.
The bat is either 12 or 8 colour clocks wide in the
Auto mode.
So there you have it. Blockbreaker playable with
paddles, joystick or even a Touch Tablet! If you get hooked on it you may
find that you want to go and get some paddles after all, especially if you
want to get as good as that Auto mode!
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