One thing is strange, however. Are you trying to tell me, that a system which could possibly display 100 objects on the screen, has the same sound capabilities as 2600? 2 channels? With that lousy limited pitch? Can something be done with this? I'm a bit surprised (and it isn't nice surprise).
There is an audio recording of a panel discussion of the GCC designers at the 20th anniversary party for the 7800. In it on of the hardware designers mentiones that that had ideas for a better sound chip, but didn't implement it, because they had so little time to finish the design of the MARIA graphics chip. So they were planning of creating a cheap sound chip later that could be put on all game cartridges or possibly on one sound passthrough cartridge. But since there were problems with the Tramiels when they took over Atari, GCC never finished the sound chip, and the audio connection on the cartridge port was only used by Ballblazer and Commando, which both had an addition POKEY chip in the cart.
So unless you design yourself a cartridge with an addition sound chip in it, then all you'll get for your game will be TIA sound.
I have one more question, if I can: how does MARIA handle collision detection? Do I have to do this in software way?
Since there are no real freely moving objects, there is no hardware collision detection in the 7800. You have to keep track of the positions of your objects yourself and see if any of them collide.
Ciao, Eckhard Stolberg