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ArcEm.doc
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1997-10-13
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=======================================================================
1 About
=======================================================================
Many, many moons ago, (1979 to be specific) I was the sort of poor
malnourished urchin that used to hang around the video arcades after
school, probably while you were doing your homework... ;-)
Even now, I can still remember that first glimpse of the game
"Asteroids", the dazzling quality of those pin sharp dots of white
light, the mathematical purity of the thing... At the time I didn't
know what was making it work, but I knew I'd fallen in love...
Anyway, while asteroids was pretty wonderful, the game that really
launched the video games phenomenon was good old Space Invaders.
If memory serves, the first machines were produced by Midway and
used buttons for left and right, the later Taito versions used a
standard joystick. My favourite invaders variant though was called
"Cosmic Monsters" by Universal. As well as being a colour game, it
added novel features such as reinforcements... If anyone can get
hold of a rom image of CM I'd be ecstatic...
As a consequence of spending so much time in this environment, I
knew almost every trick in the book as far as playing the games (and
how to obtain free credits!). So, when I got my first computer (zx81)
, what I really wanted was a way of playing space invaders.
Despite all the "advances" since then, every supposed "clone" of the
game fell far short of my (admittedly perfectionist) standards.
Until that is, I saw Dave Spicer's "Sparcade", I was utterly amazed,
the only problem was that it meant powering up my lame PC to play it...
So, a few weeks back, while in an ambitious mood, I decided to have
a go at doing an emulator on the Amiga. I thought it would take a few
months to complete, and that it would be best to use someone else's
Z80 emulation package. After all, there's no point re-inventing wheels,
(not that it's ever stopped me before..)
I was wrong... After much hair pulling I decided I'd need to write my
own, simply in order to understand the thing. It took 3 days to write,
and 4 days to debug to the point where the game actually ran. Bearing
in mind I haven't used z80 in 10 years, was never that competent at
it anyway, and that I had no documentation apart from Marat F.'s
C source, I was amazed at how easy it was, and at how fast the code
ran..
So.. here we are. The emulator is actually emulating an Intel 8080
(the z80 was a deluxe 8080 compatible), and it currently runs 4 or so
games (AFAIK), albeit imperfectly in the case of Lunar Rescue.
These are:
Space Invaders
Space Invaders Deluxe
Lunar Rescue (still buggy)
Space Attack II
Space Invaders Revenge (still buggy)
Once I have the energy, I'll probably attempt to emulate Pacman,
Galaxians etc etc.. but I've no idea how easy or difficult it'll be,
so no promises. Oh, and don't hold your breath waiting for sound,
it's a tricky job, plus I have no idea how to use audio on the
Amiga... sorry.
=======================================================================
2 Installation & Usage
=======================================================================
1) Unarchive - Then put the ArcEm drawer wherever you like.
2) Get hold of some Roms - see (*)
3) Put them in the roms drawer
4) Double click one of the icons.
5) Hit 3 to insert a coin, 1 for 1P, 2 for 2P. P to pause, R to resume.
6) Use joystick to move about etc.... perhaps pressing the fire button
every so often, to add a bit of variety ?
7) Edit the ArcEm.cfg file and modify the speed to taste. 20 seems
about right for my machine (28 Mhz 020), but you'll need to change
it if you have a faster/slower machine.
8) After: a) Wiping away tears of nostalgia.
b) Puking at the primitive graphics. (delete as appropriate)
Hit Q to quit.
(*) Wot No Roms !?
You'll need the machine roms of course, where you get these from is
a bit of a dilemma really isn't it... You could take the easy route
and just grab them from a web page perhaps.. but was life supposed
to be that easy ? Remember, anything that's fun and doesn't require
subservience before you get your carrot is probably very naughty
indeed...
Right, that's my audience reduced to those with a pragmatic approach
to "intellectual property", and possibly one or two rich buggers who
can afford the original machines. For the sake of unreality I'll
assume this program will mainly be used by the latter category.
Once you get them, it's probably best if you put them in the drawer
provided, which, funnily enough is called "roms". Assuming that the
names of your set of roms are exactly the same as those listed in
the ArcEm.cfg file, you can then simply click the appropriate icon
and start playing. Otherwise, you'll have to rename the roms, or
edit the names in the cfg file, whichever you find most fulfilling.
One more thing, if you're having difficulties finding the roms,
DO *NOT* MAIL ME ASKING FOR THEM!! Under no circumstances will I send
you any. Nope, not even if you're an aol customer!!
[ Clue: Try AltaVista. search for: +mame +roms ]
=======================================================================
3 Space Invaders tips & secrets.
=======================================================================
Here's a few tips for playing Space Invaders, I'll assume you already
know the basic strategy as far as trimming widthways first as opposed
to randomly.
1) If you want to get a 300 point bonus, you need to fire 22(?)
shots and then hit the "beefy" (spaceship looks like a beefburger)
with shot no. 23. After this, you need to hit it with every 15th shot
for a 300 every time. [Score is obviously a function of (shots fired
modulo 15) ]
2) You will continue to get spaceships (or "beefies") at regular
intervals until the fleet is reduced to less than 8 invaders.
3) When an invader is sitting on the very last row before it invades,
it can't touch you.. You can sit under it's nose all day and not feel
a thing. This forms the basis for what we called "the method", you
produce a box pattern with one straggling invader to avoid being
cornered, then slowly remove layers until you're ready to finish off
the final few.
[see method.gif in pics drawer]
4) The invaders which shoot tend to be on the extremes. So if they're
uncomfortably low, don't finish off the current column, make a start
on the next one before killing the top guy.
5) Every so often you get what we used to term a "dead" invader, this
usually happens when you are shooting at the barriers at some distance
from the fleet. Suddenly one invader freezes and becomes a dead
unmoving lump of pixels.. I've no idea why, but it's a fun little bug.
[See dead.gif in the pics drawer]
6) Even more rare, but much more nasty is what we used to call a
"freak invasion", for no good reason the invaders would wise up to
the fact that marching left and right was inefficient and simply
head vertically downwards... Frightening as hell when it happens the
first time. (It's never happened to me yet during an emulated game...)
7) Each wave the fleet starts at a lower initial height. I think there
are 9 waves before they go back to the height of wave 2, we called this
"sending them up". My record was two and a half cycles.
[ Even when they go back up, by that time they are positively *spewing*
missiles, so it's not that much of a relief. ]
Actually "clocking" the score is much easier... I think my best was
(2)4000 or thereabouts.
=======================================================================
4 Credits
=======================================================================
Dave Spicer, Neil Bradley, Marat Fayzullin for their contributions
to the arcade emulation scene.
Diddler, Smiffy, Tucker and all my other partners in crime, who hung
out down "the front" in Redcar back in the early 80's... happy days...
=======================================================================
5 Program Status
=======================================================================
ArcEm is freely distributable, but remains © Andrew G Bennett.
The game roms are not.
Donations are welcome, but not required.
If you'd like to encourage me to spend my time doing further work on
arcade emulation, as opposed to my other interests, send your bribes/
postcards/whatever, to :-
Andrew Bennett
24, Norwich Road,
Redcar,
Cleveland.
TS10 3RX
Or, if like me, you're financially challenged, just send a nice email
[ I'm a sucker for praise... ]
To ensure you get through my spam filter, email me at:
arcem@gauss.demon.co.uk
On the subject of spam, you can also pick up Poppy, which is capable
of killing 90%+ of UCE/Spam on my amiga web page:
http://www.gauss.demon.co.uk/amiga.html
This will be the best place to look for updates of ArcEm too...
=======================================================================
6 Version History
=======================================================================
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
V 0.3 13/10/97
o IN(3) hardware emulation bug finally fixed! Lunar Rescue works!
o Added cute GELS option so each game can have it's own overlay...
o Added port definition, (and removed auto cheat mode on SI pt II)
o Menu strip now hidden (for the time being..)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
V 0.2 07/10/97
First public (Aminet) version.
o New display driver which allows a vertical display.
At last, no more aching neck!!
o Added joystick routine.
o Almost solved the IN(3) problem, still not quite right though - problems
with lunar rescue.
o DAA instruction still buggy. (eg Fuel countdown on LR)
o Invaders Revenge keeps restarting intermittently - port problem ?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
V 0.1 16/09/97
First useable version, horizontal display, not publically released.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -