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 My original 7800 Games 7800basic Programming | Touchdown Challenge 7800 | Smashteroids Demo | Adventure Demo
 Map Tutorial  | Graphics Tutorial |
Original 7800 Source Code | Dungeon Stalker | Boom! | Death Merchant | Legend of Silverpeak
 
 
 
 My Original 7800 Games
 
Below are the Atari 7800 games and demos I've written to date, along with bookmarks to a few tutorials I wrote at the bottom of this page.  I provided download links to the binary files for emulators for convenience, but each game has it's own section with additional downloads and screenshots.
 
 Touchdown Challenge 7800    Death Merchant    Legend of Silverpeak   Boom!   Dungeon Stalker  
       

 
                   
Games and Source Code (a78)  

Description

 
Adventure Demo   Multi-room Adventure demo featuring the original map from the NES classic.  
Smashteroids Demo   A space shoot'em'up game inspired by the Intellivision game Astrosmash  
Touchdown Challenge 7800   A football game inspired by the iOS game Kickoff.  
Boom!   A game inspired by the 2600 version of Activision's Kaboom.  
DungeonStalker_(version 1.232)   An arcade style game inspired by the original Intellivision game Night Stalker (updated 7/8/15)  
Legend of Silverpeak   An expansive RPG, fully playable but incomplete.  
Death Merchant   A remake of the classic DOS game DopeWars.  Playable but incomplete.  
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Tutorials  

Description

 
Creating 7800basic graphics   A tutorial on how to create graphics that are compatible with RevEng's 7800basic  
Creating 7800basic maps   A tutorial on how to create maps that are compatible with RevEng's 7800basic  
       
 
 
     
 
 7800basic Programming Environment
 
       
  7800basic is a programming environment created by Mike "RevEng" Saarna, it is based on Fred Quimby's batariBasic. 7800basic is a BASIC-like language for creating original Atari 7800 games. It is a compiled language and the compiler runs on a computer, but it creates a binary file that can be run on an Atari 7800 emulator or used to make a cartridge that will operate on a real Atari 7800. It runs under Windows, Mac OSX or Linux. 

Mike is also part of the team that updates Mame and A7800.  I highly recommend you use A7800 for playing 7800 games in emulation.  It is the most current and accurate 7800 emulator in 2020.

 
       
Source  

Description

 
7800 Basic   The official site for the lastest version of 7800Basic.  
Link to RT for latest documentation   Random Terrain maintains the current version of the instruction manual on his site.  
 
7800 Emulation  

Description

 
 A7800   You'll need an emulator to play your 7800basic games on a computer.  Download the latest version of A7800.  
 Atari 7800 BIOS Files   You'll need the BIOS files to use with the emulator.  
 
     
 
   
 
 Legend of Silverpeak

 
This is an expansive and fully functional and playable 512KB RPG game for your 7800!  While the game is playable and beatable, I never fully finished everything I wanted to do to it.  First, Here's the story...

You are Azťmar Rehn, a simple woodsman from Mountain Home Grove, a beautiful patch of forest just east of the Silver Mountains. You set out from your homeland to reunite with your Uncle after your father's death. Unfortunately, upon your arrival, your Uncle is no where to be found. A short note is left in the Cabin, but it's not as helpful as you'd like it to be.

You'd heard of the war, and how all the most virtuous crystals that were revered by the people of Midlothia were captured and scattered into the deepest dungeons. They are fiercely guarded by powerful men who are determined to crush the will and spirit of the people. Without their beloved symbols of virtue, the entire realm had been taken over by mercenaries and theives, bent on taking whatever they can for their own selfish gain. No power or virtue of man could ever have deserved that, what has been fated should not have taken place. Feelings of hopelessness and misery abound, and no one has risen to the challenge of ridding the land of these thieves.

No one with good intent, that is. One powerful warrior, who calls himself Nonnag, who's mere prescences strikes fear in the hearts of men, has spread his evil throughout the realm. He created the the Crystal of Wrath, which serves as a beacon for those who serve his evil purposes. It must be captured and destroyed in order to bring peace, light, and life back to Midlothia. The common people are waiting for a hero to emerge. Once who can vanquish the evil, recapture the crystals, and restore the rod of life. Only this man is worthy of being crowned the next King of Midlothia. Great crisis produce great men and great deeds of courage.

The Midlothian army has long disbanded. With their tragic losses and lack of leadership, hope was lost. Soldiers are citizens of death's grey land, drawing no dividend from time's tomorrows. It is now up to Azťmar to restore order, to agree to the ultimate sacrifice for the sake of his homeland. As soon as sacrifice becomes a duty and necessity to mankind, there is no limit to the horizon which opens before him. It's time to fulfill your destiny.

Next, Here's what I never finished:

1) When you enter and complete each dungeon the crystal is not guarded. It was my original intention to add a boss fight in each dungeon, right now when you get to each last dungeon screen you can simply pick up the crystal with no fight.

2) Loading and saving to the AtariVox is not currently functional. You can use save states in emulation on A7800/Mame/Mess, however.

3) There is a slight screen flash when you switch rooms that very briefly shows unintended graphics on the screen. This is likely due to me overrunning the capabilities of the MARIA graphics chip in screen transitions and I have not yet addressed that.

4) In the graveyard area you will be randomly attacked live by skeletons rather than the typical turn based attack. I did notice some strange character movement issues during this attack sequence, in some cases you may not be able to move in areas that you otherwise should be able to.

5) I have a defined level progression in place, but because of the long amount of time it takes to actually play the game it's not well tested for game play balance. Same goes for the progression of how quickly you can earn gold with monster fights vs.  How much it costs to continue to purchase health potions and other items, it's not well tested for balance as you progress in the game.

6) Some items you can buy in the marketplace have no actual function in the game.

7) There are no sound effects and there is no music, right now this game is completely devoid of audio.

Download  

Description

 
Legend Of Silverpeak   Legend of Silverpeak, original release, v1.0  

One file to rule them all! :) The zip file includes all of source code and all of the files needed for compiling Legend of Silverpeak. Note that there are lots of spoilers here... If you dig into the source code you'll find all the info on the storyline, game events, and exactly how to beat the game, and I have complete game maps of the overworld and the dungeons included in the image files. All I ask is that if you not rip off the graphics and re-use them in your own game, other than that the source code itself is fair game if anyone wants to try their hand at creating an RPG with 7800basic. Hundreds and Hundreds of hours of work have already been poured into this.

The source code contains lots of extended ASCII characters and I use Microsoft's free Visual Studio Code as my editor. It all lines up and looks great in VSC, your mileage may vary with how it looks in other editors. Also, I didn't completely clean up all of the graphics files, there are more included than I actually used in the game, many are simply older versions that were later revised and given a different file name. The overworld/dungeon maps I created are slightly outdated. Overall room connections are the same, but some images were altered.

 
Screenshots


 
 
 



 

 

 

 
         
 
 
   
 
 Death Merchant

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Death Merchant is a remake of the classic DOS Game DopeWars.  This game is playable but incomplete, and has a few bugs here and there.

Special Thanks to David Exton for creating the amazing artwork.  There was (still is!) a planned release of this game on cartridge at the AtariAge store, I simply need to address the bugs and complete the game.

Welcome to the Apocalypse.

Death Merchant is a new 7800 game that was inspired by an old favorite of mine, Dopewars, which can be downloaded here. Dopewars is a DOS based text-only drug dealing simulation game and I used it's gameplay in this re-imagining of the original, along with some graphics and gameplay additions to give it a bit more of an RPG-like feel. Itís a 48K game written almost entirely in 7800basic, there are some assembly subroutines for the 24-bit math calculations. For the curious, I also wrote a Win9x version of Dopewars back in the 1990's, it was closer to a clone of the original. It won't run well (if at all) on Windows 7+, but fee free to check it out and download it on my home page here.

The game is set in a post-apocalyptic world, and the object of the game is to survive for 31 days and earn as much money as you can in the process by buying and selling survival gear. You set out with a $5000 loan for a month in the abyss, looking to earn as much money as you can while surviving your journey. Youíll have to deal with random events that occur when travelling that can help or hinder your progress. When the game starts, youíre presented with a main menu of options at the bottom of the screen: Buy, Sell, Bank, Stats, Travel, Doctor, Train, Fight, Lender, and Rest. On the top half of the screen youíll see your current stats, your cash, and your current location on the left side, and on the right side youíll see all of the items available for trade, the current prices, and the quantity of each that you currently own.

Progressing in the game requires that you travel, that's what triggers the start of the next day. Certain options are only available in certain cities so you'll need to travel to specific destinations based on your current needs in the game.

While the game has been tested and seems to work fine, this is not likely to be the final release and there may still be some undiscovered bugs. I may make revisions and post updates in the coming weeks (months?) as I make tweaks to the game. Certain stats may be adjusted as I play more to try and improve the balance of the game. Thereís a lot going on, and Iím still working on making sure the game isnít too easy or too difficult. Feedback about game play balance or any other suggestions would be appreciated. Major changes would be impossible at this point as the ROM is 99.9% full - notable changes would require removing existing features or functionality. It is possible to roll your score if you exceed $999,999, although I did attempt to make it impossible (or very difficult) to actually do that.

This game does not feature any AtariVox speech nor does it offer high score saving, and Iím aware that in-game sounds are somewhat limited. In that regard this game stays true to the spirit of the original. Iím limiting myself to 48k with this game (mostly because Iíd need almost a complete re-write at this point to use bankswitching), and adding those features isnít possible due to space constraints.

Below is a description of all the player stats and menu options to get you started. For emulation I highly recommend Mame over ProSystem, the colors look bad in ProSystem with this game. Mame is much more accurate. I haven't taken the time to test this on real hardware yet, but I am providing the .bin for anyone who'd like to try it out that way. Enjoy, and let me know what you think!

Statistics and Consumable Items

Knives
Knives are needed when you get attacked when travelling or when you start a fight. If you donít have any knives, you will not be able to continue fighting or initiate a fight. Knives can be acquired by purchasing them from the Merchant or by randomly finding them when you travel. You may break or drop a knife when fighting. You start the game with 25 and and carry up to 99.

Health (HP)
Your health, or hit points, must remain positive or the game will end. You can lose health in two ways: by travelling when your Stamina has reached zero (-2 per day), or when you are attacked and hit by an enemy (-1 per hit). The only method to increase your health is to visit the Doctor in the city of New Vegas. You will be charged a random fee for your visit. You start the game with 99 health points, and the max value is 99.

Backpack
Your backpack is an extremely important item in the game, managing the amount of space you have is critical to success. You start out with a small backpack with enough space to hold 50 tradeable items. Your knives and food have their own inventory limitations and do not affect the amount of backpack space you have. When travelling, you may have an encounter with the Merchant, who will sell you a larger backpack that increases your usable space from 50 to 99. You may only buy the larger backpack one time per game, 99 is the maximum number of items youíll ever be able to carry at once. As the ability to store items is key to success in this game, itís recommended to upgrade your backpack at the first opportunity.

Food
Food is necessary to maintain your Stamina level. Food can be acquired by either Resting at the safe house in Bedford, purchasing it from the Merchant (who appears randomly when youíre travelling), or by randomly receiving rations when travelling. If your food supply falls to zero, you have an additional daily stamina drop of -1 in addition to the normal drop of -3.

Stamina
Stamina reflects your overall energy level. It affects your ability to fight, and also your health when it reaches zero. You cannot start or continue to fight if it reaches zero. You will lose 2 stamina for every day that you travel. The only way to replenish your Stamina is to rest in the safe house for one day, which is located in the city of Bedford.

Charisma
Charisma has two main effects in the game. Making purchases from the Merchant is what increases your Charisma. Once your Charisma reaches a certain level, you will receive more and more free items from the Merchant with every purchase you make from him. Higher Charisma levels will also start reducing the interest payments you make on your debt.

Dexterity
The higher your dexterity, the more likely you are to win a fight. You start out with a Dexterity value of 10, and will earn 1 bonus point for every criminal gang you defeat, and 5 bonus points every time you purchase professional training.

Menu Options

Fight
Fighting is random or manually chosen. You may be attacked when youíre travelling to a new city, or you can manually start a fight from the main menu at any time and in any city that youíre currently in.
When entering a fight, you will encounter a random number of criminals in a gang. During the fight, additional criminals may enter the fight, prolonging the battle, and in some cases you may not be able to escape and must complete the fight until youíve exhausted your Stamina or knives, your Health is depleted, or you kill all of the gang members. Hits and misses are determined randomly, however the more often you fight the more likely you are to win (as your Dexterity stat increases). When you defeat an entire gang of criminals, you will gain a dexterity bonus as well as some cash and extra knives.

Travel
Travelling is a requirement in the game in order to progress. Travelling to a new city offers fluctuations in the price of goods, allowing you to make some big profits if youíre lucky. It will also result in many different random events occurring. Random price events may occur on some goods, resulting in dramatic price increases or price drops, you may find some money, food or knives, you may be attacked by a gang, or you may be stopped by the Merchant.

Lender
The Lender is the antagonist of the game, you start off owing him the amount of money that you start the game with. You Start with $5000 in debt and immediately have that much available to you. Itís a one time loan, you cannot borrow any more money during the game, you can only pay him off. Interest is charged daily, but the amount of interest he charges is modified by your Charisma and the number of days remaining in the game. Once Debt is paid down to zero, no additional interest is accrued and you are done with the lender for the remainder of the game.

Bank
Money can be deposited to prevent it being taken from you in a robbery when travelling, and also to accrue interest. Any deposits into the bank will result in a $500 per day interest payment, which increases to $1000 a day once you have more than $10,000 in your account. You cannot spend money that's in the bank, it must be withdrawn first and you may only visit the bank when in the city of Lost Angeles. There is no fee for Bank transactions.

Rest
Resting in the safe house in the city of Bedford is the only way to replenish your Stamina, and is also a way to increase the amount your food rations. Resting is free, but it does cost you one day of game time.

Train
Training is offered in the city of New Salem. For a fee, an expert will instruct you in the ways of knife fighting, which results in a +5 Dexterity bonus every time you train. Training costs a random amount of credits. You can train as many times as you want up to your Dexterity limit, at which point the trainer is no longer available.

Stats
The stats screen is informational and does not affect the outcome of the game. It will display some additional in-game statistics: the number of times you've trained, your total Dexterity bonus, your total Charisma Bonus, the number of gangs youíve killed, the number of days youíve rested, and the number of bank transactions youíve completed. You can freely go back and forth from this screen with no penalty, and it can be accessed when in any city. The stats screen is also the "Game Over" screen when you die or run out of days, which you can use to track your scores and stats to try and do better the next time around.

Doctor
The doctor can only be visited in the city of New Vegas and is the only way you can replenish your health. The doctor charges a random fee, and will restore your health to the full amount (99).
The doctor is only available if your health is below 99 and you have enough credits to pay him.

Buy/Sell
You can select items to buy or sell only one item at a time. Move the joystick up and down to select the item youíre interest in, then move the joystick left and right to change the quantity of the item youíd like to buy or sell. You will not be allowed to buy more of an item than you can afford, and you will not be able to sell more of an item than you posess. The space available in your backpack is also verified, you will not be able to purchase more items than you can carry. After an item has been bought or sold, you are taken back to the main screen. The Buy and Sell screens can of course be accessed from any city in the game.

Merchant
The Merchant randomly appears throughout the game, generally around 0-3 times, but it's random. The items he offers are the same every time, and the prices are static throughout the game.
The Merchant is the only way to purchase a bigger backpack, and the only way to purchase Knives and food. You gain Charisma with every purchase you make from the merchant. As your Charisma increases, the Merchant will give you more free items with every purchase. As your Charisma increases, the amount of interest you pay on your debt to the Lender decreases.

Here are the known bugs, noted in November 2018, playing with ProSystem Emulator, which I don't actually recommend. Use A7800 or Mame!  These are just some random notes I made while playing.

When the death merchant gives you free items, and your backpack is still 50, it will allow you to go over 50.

If your backpack is still at 50, the max value to buy should also say 50.

One time, went to the bank for a withdrawl, and the number started auto counting down from 999,999. Left and came back and it was back to normal.

Death Merchant screen issue again. Just bought the expansion, then started buying canteens. The left number would count down by threes, and I could...
seemingly buy as many as I wanted without regard to the size of my backpack. I had $130,000 to spend. I ended up owning hundreds of items.

Again - another death merchant screen, and I could buy as many knives as I wanted, backpack space didn't matter, it just stuck at zero but I could
keep buying knives and my total cash would keep dropping. Not sure if knives are even set up to use backpack space, or should be?  Need to check.

12 days remaining and I had $780,000. I think it's still too easy to make that much money - maybe being too generous with the handouts from the merchant.

With 12 days remaining I had yet to have a single enemy encounter. First random encounter with 7 days remaining.
 

Download  

Description

 
Death Merchant 1.0.a78   Death Merchant a78 file for use in emulation, Mame or A7800 recommended.  
Death Merchant 1.0.asm   Death Merchant Assembly  
Death Merchant 1.0.bas   Death Merchant 7800 Basic Code  
Death Merchant 1.0.bin   Death Merchant Binary File for use on real hardware (Cuttle Cart 2)  
Death Merchant 1.0_Graphics   Death Merchant Graphics Files, for use in compiling the code with 7800Basic  
 
Screenshots



 

 
 
 


 




 


 

 

 
         
 
 
   
 
 Dungeon Stalker

 
Dungeon Stalker is an arcade style game written as an homage to Intellivision's Night Stalker.  Many gameplay elements were taken from Night Stalker but there are key differences that I think improve the game.  It was written along with RevEng from AA, I couldn't have done it without his help.  

This game uses the much lesser used 320A mode which allows for a much higher resolution at the expense of single color sprites.  I chose it because I thought it was a perfect fit for a game designed to look and play similar to Night Stalker.  It also supports the 7800 high score cart and AtariVox saving and speech, there are three dozen unique speech phrases in the game.  There are plans for artwork and an instruction manual, neither of which are completed yet.  I higly recommend downloading the PDF version of the manual, as it describes key features of the game that you'd otherwise miss.  The boxed release of the game will include a brand new manual designed by David Exton.

It's complete!  Version 1.245 is the final version of the game that will be released on Cartridge (and a box & manual) for the first time at the Portland Retro Gaming Expo on October 17th, 2015. Shortly after the show it will be available as a general release in the AtariAge store.

 Gameplay Video  

 

 

Here is a video demonstration of the gampelay for Dungeon Stalker (v1.232, not the final release), created by AtariAge user Trebor:  https://www.youtube.com/watch?v=sj4_JzNFqBc

Download  

Description

 
DungeonStalker_1.245.a78   Dungeon Stalker v1.245 binary for use in an emulator (Final Version)  
DungeonStalker_1.245.bin   Dungeon Stalker v1.245 binary for use on real hardware (Final Version)  
DungeonStalker_Dev.zip   Dungeon Stalker Development Files (binaries and a78 files from version 1.00 to 1.232)  
DungeonStalker PDF Manual   Dungeon Stalker v1.245 Instruction Manual (Rev c)  

Note that the screenshots below are not from the final version, although they are very similar.  There were a few changes to the maze and sprites in the final release.
 
Screenshots



 

 
 
 

 



 

 

 

 
         
 
 
     
 
 Boom!
 
The basic gameplay of Boom! is similar to Activision's Kaboom. There are 5 levels that get progressively faster, once you're on level 5 the speed doesn't change. There is no paddle support, use your joystick to move the bucket(s) back and forth. Your bucket will wrap to the other side of the screen when you reach the edge, it makes it a bit easier to get to bombs on both edges of the screen. You start with three buckets, if you miss a bomb you will lose one. You get 10 points per bomb caught. Once you've lost all 3 buckets you will go back to the title screen and your current score will be displayed.

You can view the original development thread on the AtariAge forums here.

Source  

Description

 
boom15.bas.a78   Boom! binary for use in an emulator  
boom15.bas.bin   Boom! binary for use on real hardware  
boom15.bas   Boom! 7800bas Source Code  
boom15.asm   Boom! assembly  
boom15.zip   All Boom! files, including the graphics files, for compiling in 7800basic  
 
Screenshots





 
 
     
 
     
 
 Touchdown Challenge 7800
 
The object of Touchdown challenge is to run to the top of the field to score touchdowns while avoiding being tackled by the other team.  The patterns of the opposing team will change, and some levels have a single player on the other team that will relentlessly chase you down.

You can view the original development thread on the AtariAge forums here.

Source  

Description

 
football8.bas.a78   Touchdown Challenge binary for use in an emulator  
football8.bas.bin   Touchdown Challenge binary for use on real hardware  
football8.bas   Touchdown Challenge 7800bas Source Code  
football8.asm   Touchdown Challenge assembly  
gfx_football.zip   Touchdown Challenge graphics files, for compiling in 7800basic  
 
Screenshots





 
 
     
 
     
 
 Smashteroids Demo
 
Smasteroids was written in an afternoon as an homage to the original Intellivision Astrosmash game.  It is just a demo and no further development is going to take place.  It is included as a sample game in the 7800 basic distribution.

You can view the original development thread on the AtariAge forums here.

Source  

Description

 
astrodemo8.bas.a78   Smasteroids binary for use in an emulator  
astrodemo8.bas.bin   Smasteroids binary for use on real hardware  
astrodemo8.bas   Smasteroids 7800bas Source Code  
astrodemo8.asm   Smasteroids assembly  
gfx_astro.zip   Smasteroids graphics files, for compiling in 7800basic  
astromap.tmx   Smasteroids Tiled Map file  
 
Screenshots
         
     
 
     
 
     
 
 Adventure Demo
 
This demo is a large open world adventure map that you can roam around, and the demo uses graphics similar to Nintendo's classic.  I've fairly accurately replicated the original graphics and map, although it is modified a bit due to the 7800's lower 160A mode resolution. It is a map you can walk around, it isn't a playable game. 

Before the Nintendo lawyers start scrambling to send me a C&D letter, I'm never going to actually release a playable game with any of Nintendo's intellectual property included and I'm not going to publicly post any graphics that would allow someone else to compile my demo or any future releases with  (binary only) that lets only you explore the original map as I thought many would have fun with that.

3/18/2015 Update:  The links below have been updated with the actual completed Map Demo.  This demo accurately replicates the original map from Zelda. This is only a map demo and there's nothing to do but walk around the overworld and look around. There are no enemies, no dungeons, no weapons, nothing else. You can press the fire button to see a sample inventory/status screen. As I mentioned back in June, due to Nintendo's copyrights I won't be releasing an actual game with Zelda graphics and I won't be posting the code, graphics, or screen maps for this version. This is just a binary release to show what "could" be done.  Recreating this map was a huge undertaking.  There are a few map screens with incorrect colors and may also be bugs I never found.

You can view the original development thread on the AtariAge forums here.

Source  

Description

 
Adventure_Map_Demo.bas.a78   Adventure Map Demo binary for use in an emulator  
Adventure_Map_Demo.bin   Adventure Map Demo binary for use on real hardware  
 
Screenshots
         
 
         
   
 
     
 
     
 
 Tiled (Map Graphics) Tutorial for 7800basic
 
Here are the steps on how to create a tiled background image for use with 7800basic, specifically for a map that will work with the 160A display mode along with 'set doublewide on' in your code. It works great and is a big time saver.

Before you start you'll of course need all of your graphics images completed. If you make any changes to your tileset graphics in the future, the changes will automatically be reflected in the map. Tiled does not create an image file, it creates an XML file that maps out and links to the different graphics images that you have. If you dramatically change your graphics images you will have to update your map file (or files).

Normally the width of one character in 160A mode is 4 pixels wide, but adding "doublewide" changes that to 8 pixels wide. This is why I used "8" for the "tile width" in Tiled.

If you wanted to adjust this tutorial for another mode, you can just lookup the width of one character in that mode in the table I linked to, and adjust for "set doublewide on" if you use it. That will be your value for "tile width". The "tile height" will be your zone height, and you can adjust the map size as you prefer.

First, download the Tiled app.

       

  Once you've installed it, select File | New Map.  
       

  Make sure you select the correct options for your new map. Select an orthogonal orientation, XML format, 20x12 map size, and 8x16 tile size.  
       

  Now your ready to load up your tileset graphics. You can load multiple sets.  
       

  Click on browse to select your tileset. Make sure you set your options as seen in the screenshot.  
       

  Your first tileset is now loaded. I generally increase the size to 400% to make it easier to see.  
       

  You can now left click on a tile to use on the map, or hold down the CTRL button and select multiple tiles at a time.  
       

  You can now draw on the map screen. If you hold the left button mouse down you can drag the background tile to fill the map screen.  
       

  You can load multiple tilesets, each one will get their own tab. I generally increase the map size to 200% to make it easier to see.  
       

  Once you're happy with your map design you can save it as a tmx file and use it in your 7800basic program.  

 

 
 
     
 
 Graphics Tutorial for 7800basic
 
I spent a great deal of time trying to figure out how to create 7800basic compatible graphics with my first game, so I thought I'd share the steps I took to make it work. Using Gimp is the easiest way to get started, you can download it here.
 
       
  First, open the 7800basic palette file, which you can download here.

a closer to accurate layout of the 256 color Atari (NTSC) palette here: ATARI256_26.7x6LG.PNG

Here is the *.act file which can be imported: Atari256_267NTSCx6.zip

Or a more 'brillance neutral' palette here: ATARI256_26.7x0LG.PNG

Here is the corresponding *.act file: Atari256_267NTSCx0.zip

They are both set with a 26.7 degrees phase shift and not manually hand-picked, that better matches the documented as well as 'real hardware' results of the systems.

 
       
  Next, click on Windows | Dockable Dialogs | Palettes, we need the Palettes dialog box to be open.  
       
  Next, right click on the palettes dialog box and click Import Palette.  
       
  Once the window is open, click on Image, Palette name (rename to Atari7800), and click on Import.  
       
  Click on Image | Mode | Indexed.  
       
  Click on Generate Optimized Palette and change the number to 13, then click on convert.  
       
  Change setting back to RGB, just so we can go back and change it to Indexed again to make one more modification...  
       
  Click on Image | Mode | Indexed again to make one more change.  
       
  Click on Use custom palette, then the button next to it.  
       
  Click on the 7800palette that was just added, then convert.  
       
  Click on open image, and open the tileset_rocks image from one of RevEng's samples in the distribution.  
       
  Click on View | Zoom | 800% so you can actually see the image on the screen.  
       
  Resize the window so you can see the entire image.  
       
  Click on Windows | Dockable Dialogs | Brushes, we need the brushes dialog box open.  
       
  Change brush size to 1.0. Go to Windows Menu | Toolbox or press CTRL+B to open the Toolbox Tool Options if you don't see it on screen.  
       
  Click on color picker tool and choose one of the four colors to modify the image. The colors in this image don't matter yet, as they are changeable with the PxCx command in the code. One of the colors is transparent and will take the background color.  
       
  Click on the brush tool to change the image.  
       
  Use the brush tool to modify a 16x16 area, there are three side by side in the samples from RevEng, each is 16 pixels across. Don't worry about the colors, as they are set with the PxCx commands in software. You can use the same colors in the sample images.  
       
  When you're done, click on File | Export As to save  
       
  Export the image as a PNG file and you're ready to go.  
       

 

 
 
     
 
 Original Atari 7800 Game Source Code
 
These are original, commented source code files from the original Atari 7800 developers.
 
Source  

Description

 
Centipede   7800 Centipede Source Code  
Commando   7800 Commando Source Code  
Crossbow   7800 Crossbow Source Code  
Dig Dug   7800 Dig Dug Source Code  
Food Fight   7800 Food Fight Source Code  
Galaga   7800 Galaga Source Code  
Hat Trick   7800 Hat Trick Source Code  
Joust   7800 Joust Source Code  
Ms. Pac-Man   7800 Ms. Pac Man Source Code  
Robotron   7800 Centipede Source Code  
Desert Falcon   7800 Centipede Source Code  
Super Stunt Cycle   7800 Super Stunt Cycle Source Code  
Xevious   7800 Xevious Source Code  
Base 7800 OS PAL   PAL 7800 OS  
Base 7800 OS NTSC   NTSC 7800 OS