Update, guys!
I think it was lovablechevy who thought using plug'n'plays were a simple matter - I can report actually it isn't - harder in some ways to regular systems.
Take something like an N64 or SNES or whatever, do one and you are fast at making a second one (you know what to expect and what you are doing after all), and systems like the SNES are only a matter of connecting power, grounds, video and audio and you are set.
Plug'n'plays are a similar beast, of course, but they are quirky and each one is different and wired differently. Making them into game carts is a bit like making half a portable with each one and making them cram into a small space means relocating some parts.
To give some ideas of problems:
Namco - Pacman, Galaxians, Dig Dug, Rally-X, Bosconian: this one wasn't too difficult, quite standard stuff, had some teething issues, but works reliably now.
Space Invaders (Taito / Radica) - Space Invaders, Lunar Rescue, Colony 7, Qix, Phoenix: tempremental; took external power but not internal. Turned out the LED was very picky about wire length and thickness. Took a few hours to work this out and fix (fine now).
Intellivision - (a few games) - nothing like I have seen before - it doesn't use common grounds (WTF!), and the grounds for the d-pad is different to the button controls. Got the board carved up and carefully re-wired, got video and sound but controls refused to work. The system uses capacitors on some parts of the grounding, so I guess the system registers keypresses by voltage changes or whatever. Going to have to try this again (lost a day work on this). Will have to fold the board up on next attempt to keep everything as intended, and wire to everything.
Point is that it is not as easy as you might imagine!
I am getting used to making a cart from scratch and wiring to the traces, etc of the game cart.
Getting my batteries today (yay) so once they come, I will spend the rest of today, and part / all of tomorrow hacking the back of my case and getting the case sides on.
I will have this project finished, it is just a matter of how many add-on carts I make in the time. (I only need one, made two so far). I am hoping to make another one and also get a GBA system incorporated too. These boards are larger, will need to be creative with the cart design. The GBA can be tempremental (going to try a different tv-out card if I can), and will take a lot of work, so may not be able to complete it before deadline finishes.
I will have my entry entered in time!!
Anyway, pic of my two carts, both work great.
Got the artwork from arcade picture sites with marquees, and cut and pasted them into my artwork. Colony 7 was amazingly hard to find, found one site (only) with a flyer, so used that.

Irrespective of the GBA, I will do one of those 128-in-1 game type NES games as system three.






