So, the second player waits for a dragon to come on the screen, and then he can take control of it?
Basically, yes. You can control the dragons while offscreen too, but you can't see where they are going.
I think this game needs a two player linky option.
I may be leading up to that. I first need to figure out what data needs to be shared. Since the game relies on hardware collision registers, controller data is not enough. At the very least, one byte per frame?
Slave needs joystick, collision data and console switch data from master, and maybe other things.
Joystick=4 bits, button=1 bit, collision data=3 bits minimum (?)
Although all 8 bits seem to be used, the joystick only represents 9 of 16 possible states (if we assume up+down and/or left+right at the same time are prohibited) and console switches (select and reset) may override the joystick, so they could be encoded in.
Then master only needs joystick data from slave - 4 bits. Again, since there are available states here, a 0000 could be used to signal a NAK.
To begin games in the correct state, a reset occuring from screen zero (the number screen) could first jump to a special routine that syncs up all of RAM. Should be possible with a few moments of screen blanking.
I could be wrong - these are just ideas. Of course this all requires real hardware so the development time is much slower...