Heya. I have done a lot of research on PDS engine over the years, and uncovered a bunch of stuff on how the game work. I might have something to show soonish, but in the meantime, I wanted to show some of the debug stuff I found along the way. This is from the retail PDS US, not the prototypes:
Now, the way to access those options is pretty interesting. At boot-up, the game check for a save game with a specific name, ANDROMEDA_3, and if it is present check some data in it, and use the result to enable the main debug mode. But there is a catch. While the prototype was storing this value in plain ram, and could be easily patched, the final game store it in a unused register of the master SH2 cpu, the watchdog counter register. So, it can't really be patched.
When the debug mode is enabled, a few things change. Most people who got this far would plug a second controller, and use it to navigate some of the debug menus. You could for instance hold start on the second controller while pressing start on the first one to access the debug menu on the title screen.
Now, there are much more debug stuff as seen in the video, and the catch is that the game doesn't expects a controller in the second port, but a keyboard. With debug mode enabled, it will check some keystrokes on the keyboard to toggle some of those debug screens. Some of the debug menu are still usable with a controller because the Saturn maps some keyboard keys as if they where a normal controller. There is much more debug stuff that what is in this video, like the ability to start a new game with all the map unlocked, show the memory layout,...
Yabause doesn't support keyboard input, so I hacked the code a bit to simulate the keyboard. I think mame/mess supports it to a degree, but PDS was freezing when booting up last time I tried to run it there.