Post #253,068
4/23/06 1:10:01 AM
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Medieval Mayhem
I've decided to try my hand at writing a game for the Atari 2600 and have been documenting it in [link|http://www.atariage.com/forums/index.php?automodule=blog&blogid=148&|my blog]. It's now far enough along to be playable. I recommend using [link|http://stella.sourceforge.net/|Stella] if you'd like to check it out, there are versions for Linux, OS X and yes, even Windows. Once you start the game in Stella you'll need to hit TAB then pick GAME PROPERTIES to set the Sound to Stereo and the Controllers to Paddles. Once set you'll have to restart the game for Stella to use the new settings(Apple-R on the Mac, most likely ALT-R under Linux and Windows).
Medieval Mayhem is a rewrite of the 4 player game [link|http://www.atariage.com/software_page.html?SoftwareLabelID=593|Warlords] with the intent to make it play more like the [link|http://www.klov.com/game_detail.php?letter=&game_id=10405|arcade version]. The main improvements are multiple fireballs(with more angles of motion and speed) and the dragon that starts each round(though the dragon graphics aren't in place yet).
"Why is he coding a game for that old Atari?" you might ask. "Well," he says, "it's a challenging piece of hardware to write for." The specs of the machine are:
128 bytes of RAM (yep 1/8th of a KB)
4 KB of addressable ROM(my game uses 16KB via bankswitching)
0 bytes of Video RAM
1MHz 6507 - a 6502 that's missing a few address lines(hence the 4KB ROM limit) and IRQ
The 0 bytes of Video RAM is part of what makes the Atari so challenging to code for. For video the Atari uses TIA, a chip that has a few registers to generate a single line of video line at a time. The registers control the playfield (the blocky background), a ball, 2 sprites and 2 missiles. The program spends most of it's time feeding the TIA's registers to generate the display. It's so primitive you even have to tell it when to send the vertical sync to signal the start of the next video frame. If you time your code incorrectly you may end up with sheared graphics or even a rolling picture.
You may be wondering about the "set the sound to stereo" comment for Stella. When the Atari was designed the other home video games(ie: Pong) used a built in speaker to generate sound, the TV was only used as a display. The Atari was going to include stereo speakers and the early games were written to utilize it. However, the built in speakers ended up not being used(probably to save costs) and the audio was routed to the TV via the RF modulator instead. The holes for the speakers [link|http://spiceware.org/gallery/Misc/Atari_VCS_speaker_holes|can be seen] by looking over the backside of the Atari. The cartridge in the Atari is what I'm using to test Medieval Mayhem on real hardware. It's a [link|http://www.arminvogl.de/KrokodileCartridge|Krokodile Cartridge] and contains 512KB of FLASH ROM that can be programmed using a serial connection. I've modified my Atari to provide S-Video and stereo output(an unmodified Atari can only provide an RF signal) so I wanted to take advantage of the stereo sound for my game.
Darrell Spice, Jr. Trendy yet complex\nPeople seek me out - though they're not sure why\n[link|http://spiceware.org/gallery/ArtisticOverpass|Artistic Overpass] [link|http://www.spiceware.org/|SpiceWare]
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Post #253,884
4/30/06 4:04:29 PM
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Made some progress
A dragon now starts out each round. The guy doing the dragon graphics has finals coming up, so the dragon graphic is just a static image he did as a test. The dragon will be animated and smoothly scroll on/off screen once his semester wraps up.
The fireball capture routines are also in place. You can grab the fireball, move your shield, then release the fireball to change the direction of travel. I still need to add the "knock out your own bricks" that will occur if you hold onto the fireball too long.
I tried it out using Windows at the office and control-R is what's uses to restart the game.
Darrell Spice, Jr. Trendy yet complex\nPeople seek me out - though they're not sure why\n[link|http://spiceware.org/gallery/ArtisticOverpass|Artistic Overpass] [link|http://www.spiceware.org/|SpiceWare]
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Post #254,867
5/9/06 4:53:48 PM
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will be demoed at Midwest Gaming Classic next month
[link|http://www.atariage.com|Atari Age] is going to demo Medieval Mayhem with some other [link|http://www.atariage.com/features/shows/mgc2006_preview/|new and in development] games for the 2600 at the [link|http://www.midwestgamingclassic.com|Midwest Gaming Classic] in Oconomowoc, WI on June 3rd and 4th. Oconomowoc is 25 miles west of Milwaukee.
Darrell Spice, Jr. Trendy yet complex\nPeople seek me out - though they're not sure why\n[link|http://spiceware.org/gallery/ArtisticOverpass|Artistic Overpass] [link|http://www.spiceware.org/|SpiceWare]
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Post #254,884
5/9/06 7:32:33 PM
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Nice one!
I still haven't tried your game out, but just from reading about the development process for the the 2600, it sounds like you've accomplished a pretty impressive achievement!
In other news, Oconomowoc is a funny name, isn't it? Then again, I can almost see Woolloomooloo from here, so I shouldn't laugh too loud.
Two out of three people wonder where the other one is.
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Post #254,889
5/9/06 8:05:32 PM
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ICLRPD. (new thread)
Created as new thread #254888 titled [link|/forums/render/content/show?contentid=254888|ICLRPD.]
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Post #254,892
5/9/06 8:55:22 PM
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Thanks!
One thing that's made the programming easier is Stella now includes a built in debugger that allows you to single step the CPU. That's made finding problems much easier. I've only had a few problems using Stella: the paddles don't read correctly while debugging and I found a couple things where Stella wasn't accurately emulating the 2600. The game looked OK in the emulator, but not OK on a real Atari. Luckily I'd only made a couple changes when those cropped up so it was easy to figure out what was going wrong - basically certain registers should not be updated within x number of CPU cycles after certain other register have been updated.
I'm trying to get some more stuff done for the show, but had a major setback when my iMac stopped working last week. Apple's [link|http://www.apple.com/support/imac/repairextensionprogram/|extended the warranty] for this problem so the repair is covered. The computer worked for a couple days after the blue smoke escaped so I was able to get current backups of the important data. I dropped it off at CompUSA Thursday night and called for a status update Sunday and was told they confirmed it was that problem and the replacement power supply will be in this week; however, their Mac Tech only works weekends. So I've spent Sunday night and yesterday evening recreating my 2600 development environment on my Thinkpad under Linux - I'm only missing Linux software to use of my [link|http://www.arminvogl.de/KrokodileCartridge/|Krokodile Cartridge] which allows testing the code on a real Atari.
Yes, they do have unusual names up there. Of course, Nacadocious isn't far from Houston :-) I'd like to go but I'm already commited to being in Nekoosa, WI in for July 4th and I can't afford to make the trip to Wisconsin twice.
Darrell Spice, Jr. Trendy yet complex\nPeople seek me out - though they're not sure why\n[link|http://spiceware.org/gallery/ArtisticOverpass|Artistic Overpass] [link|http://www.spiceware.org/|SpiceWare]
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Post #254,951
5/10/06 12:39:26 PM
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We can say we knew you when!
Way to go, Darrell :)
Amy
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Post #255,026
5/11/06 2:56:56 AM
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ObSentientLRPD: "When?"
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Post #256,832
5/25/06 10:47:05 AM
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The Nicolas Seal of Approval
My friend's 7 year old was in the office yesterday. I showed him the current version and after playing a few rounds he declared "that was fun!".
Not too shabby considering he's grown up with a PS2 :-)
Darrell Spice, Jr. Trendy yet complex\nPeople seek me out - though they're not sure why\n[link|http://spiceware.org/gallery/ArtisticOverpass|Artistic Overpass] [link|http://www.spiceware.org/|SpiceWare]
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