[Coco] Arcade Game Designer (AGD) for the Coco

[oss003]

Hi guys,

I'm new to the forum but want to explain a bit about AGD because I 
ported AGD to the Acorn Atom.
The Acorn Atom has the same video processor as the Dragon and Coco, the 
6847 but in fact AGD can also be ported to other Tandy machines.

Jonathan Cauldwell has written a program called Arcade Game Designer for 
the ZX Spectrum. It's a game creation program with build-in editors. You 
can define a font, objects, sprites, blocks, screens and add event based 
script commands describing how the game runs. You can start the game 
from the menu for testing. The program is written for a ZX Spectrum 
48/128KB. It's a nice program with a good engine and a lot of games are 
written with AGD. If the game is ready, you can save it in a tapefile as 
stand alone game which runs without the editors. AGD can be downloade 
here: https://jonathan-cauldwell.itch.io/arcade-game-designer

Jonathan has also written an editorless compiler running in Windows. 
This compiler needs 2 files to generate a game: a game engine and a 
script file. The script file is compiled to an assembler file and merged 
with the game engine file. A Z80 assembler source file is generated 
which can be compiled to Z80 code. This is very interesting for porting 
AGD to the Atom because if I can convert the game engine to Atomic 6502 
code and change the compiler to generate 6502 assembler from the script 
file, you have an assembler file which can be compiled to 6502 code.

The big advantage is that the engine file is system dependent but the 
game itself, written as a script file, can be easily ported.
So the AGD system consists of:

- an general game engine file with routines to manage the game
- a game specific script file with font-, objects-, sprites-, blocks- 
and screen data and commands describing the game

The engine file can't be 100% compatible with all ported systems due to 
resolution-, colour- and memory differences. The script commands however 
can be 100% compatible so this means to run a game, you have to change 
the data and compile it for your system.

For now I have a working Acorn Atom port with more than 50 games 
working. You can see some examples here:

ZX Spectrum version Terrapins: 
https://www.youtube.com/watch?v=ea_dsXmjL90
Atom version Terrapins: 
https://www.youtube.com/watch?v=Vh4ykI0H0iE&t=53s

ZX Spectrum version Dodgy: https://youtu.be/pyMmxWgJLTo
Atom version Dodgy: https://youtu.be/P9hZtE3y31M

A lot of tests of games: https://www.youtube.com/user/oss003/videos

There are about 150 games written in AGD ready to be ported: 
https://spectrumcomputing.co.uk/index.php?cat=96&id=20176

At the moment Tony Tompson is writing an AGDX suite in which you can 
design your tiles, objects, sprites and screens.
You can also write the game scripts and the goal is to compile the game 
to different systems.
For now a ZX Spectrum, CPC and Acorn Atom port are available and more to 
come, eg. BBC and Atari.
So if a Dragon/Coco port is available, a whole lot of new games are 
available.

What has to be done to port AGD:
- Write a Dragon based engine
- Change the script compiler to produce 6809 assembler.

If anyone is interested in helping to create a Coco port, please contact 
me because there's an AGD group where the AGDX Studio is developed and 
technical questions can be answered.
I must say that it was fun to create an Atom port and the result is a 
lot of new games.

Greetings
Kees