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Welcome to CGA Jam! Sticky

A topic by Kronbits created May 01, 2017 Views: 1,528 Replies: 26
Viewing posts 1 to 12
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After the success with 1Bit Clicker Jam and after ask on twitter for a possible new one on a poll peple voted to have a new jam on June so i'm announcing it 1 Month earlier because some people arrived too late and after the jam starts still lot of people joined every day, so hope this time not be a problem.

This time is not gonna be based on a "gameplay theme",now you can do any kind of game(Platforms, rpg, racing...) using mouse, keyboard even a theremin if you want XD, only visuals restrictions using 8bit/Chiptunes sounds.

Use this forum to any thing relates to the jam and for questions about rules.

CGA Hex Values

Palette 0
yellow: #ffff55
light_green: #55ff55
light_red: #ff5555
black: #000000

Palette 1
white: #ffffff
light_cyan: #55ffff
light_magenta: #ff55ff
black: #000000

Good luck with the jam!! ;)


Looking forward to this game-jam! Quick question, could we get RGB or hex values for the specific hues of each palette? I'm getting a lot of tone, tint, and shade pollution and I'm having a little trouble extracting the core palette.

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ere you have the Hex values for the CGA palette:

the first post with the hex values for each one of the allowed palettes.

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Do we have to pick one palette for the whole game, or are we allowed to switch between the two palettes as long as we use one at a time?


After ask on twitter doing a poll and some comments yes, you can change the CGA palette 0-1 ingame

At the moment you only can use one palette fixed for the whole game, but i gonna thing about it and i will update the jam page and on twitter if this changes ;)


Out of curiosity, would writing a 16bit DOS game that uses an actual CGA mode be okay?

Any kind of language is allowed always that meets the jam restrictions ;)


My first thought was writing an IBM PC-compatible (1981) game as an OS using BIOS interrupts, but it turns out there is very little documentation on 8-bit assembly for the IBM PC BIOS. Instead, I'm aiming to use MS-DOS' QBASIC.

To be honest, writing it in pure assembly wouldn't be too bad, but it's a lot easier with qbasic or turbo pascal 6/7 in that regards. Still would be 8 or 16bit in the correct video mode.

Two questions here:

  1. Is it allowed to switch between light and dark color mode?
  2. And can the default/background color (black) be replaced with any other color?

(this was possible in the standard cga graphics modes – at least in 320x200 pixel mode)

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1- Yes

2- All that is allowed in the real CGA you can do now , but have in mind only 4 colors(Palette 0 or 1) at the same time.

If we make a 3d game, like a first person shooter for example, can we use fog to make the scene fade out (darken or lighten if using black or white fog) as depth increases?


Always that you use only 4 colors from one of the two palettes you can do a 3D game. For example for the fog yi guess you can do black/white fog with black/white dither.

Question about scanlines/filters -

Can we use a use say a 50% transparency for a screen overlay effect? Or do filters need to remain under the 4 colour palette restriction too?

The game have to be in 4 colors,for real CGA color mode. After that you can add filters for noise, glitch or whatever that yes will make the final screen have lots more colors.

Also be in mind you have to add an option to activate/deactivate filters so people can play the real CGA mode.


So in theory we could use a shader for cga composite mode (as long as it can be disabled) ;)

Could someone link an explanation of "rgba channel separation"? i haven't been able to google what it is.

I think it refers to crt-like shader effects where each color is split into its red, green and blue components:

I created such a shader for the monkey-x-nes jam in 2015:

(by the way: since someone rated this game with only one star, no one plays it – so it would be nice if someone could rate it a little bit more objective)

oh its like a tv emulator filter sorta. looks cool.

i played and rated it! it's a really cute metroidvania, much bigger than i was expecting!

heres the actual CGA spec

wiki link

There are a number of different modes depending on the resolution used, even a 16 color mode.

so... It would probably be a good thing for you to look at the spec and decide resolutions that should be used?

For this jam and as appear in rules you can use any resoluction and only choose between 2 color palettes.


To be clear, this means 16-colour mode is not allowed.


16color mode is not allowed, only 4 colors in screen to choose between two palettes ;)


Can I use Pico8 color palettes, if my game is not made in Pico8 engine?

Then why use the Pico8 ones if they are practically the same and you can do that without problem without using the Pico8 engine?

I not understand why, but well, always that fits all the rules i guess no problem.