It's official, collecting the letter 'D' is good!

I haven't posted in a while but I have been making quite a lot of progress on the RE.

I would say 90-95% of the code has been commented now. Most of the unknowns have to do with the gameplay 'AI' - variables that affect the difficulty of the game, and also a few areas of functionality that I know the exact purpose of, just not the specific mechanics. Those include unpacking background map data, and handling the movement patterns for the aliens.

The RE is somewhat complicated by the fact that there are multiple object tables; one for enemies that fire, one for enemies that don't fire, and one for the 'large' enemies - and these tables don't have the same structure! 😣 So when commenting the code, I need to remind myself which type of alien the routine is operating on. Quite annoying because they are relatively small, and it would have been perfectly acceptable to use the same structure even if some members were unused.

But I still seem to be able to make some progress each session; I think I've hit a wall but then make a breakthrough with a few variables. It's just a matter of continuing to chip away here.

On the subject of collecting 'D' from an earlier post, I can say with absolute authority that it is beneficial to the player. Here's what the Vulgus manual on Capcom Arcade Stadium on the Nintendo Switch has to say about it:

"Increases enemy firepower when it appears. Collect it to stop the effect."

Technically though, it's not about collecting them, but rather not failing to collect them. Each map area starts with a variable denoting the maximum number of enemy bullets allowable on the screen at any one time, with an absolute maximum of 6. Nothing changes when 'D' appears, but failing to collect a 'D' will increase that count by 1. Of course at some point in the game, it becomes a moot point because you'll eventually start the area with the maximum (6).

Not a 'D', but here's an 'E' just for attention

'E' & 'S' are related to other variables which I haven't examined in detail just yet.

There's also a bonus that appears at 150,000 pts and then again at every 100,000 until the last one at 550,000 pts. After that it doesn't appear again. I need to understand more about the actual bonus at this point - I've never seen it myself and was completely unaware of its existence.

I've also learned about the titular 'Vulgus' boss enemy which, again, I am yet to encounter in my own gameplay. I'll need to practice a bit more  - I'd like to get there without cheating - but I need to get my MiSTer repaired first. That's on the to-do list for the very near future. Or maybe I should install my Vulgus PCB in the lowboy and fire it up!?!