Blogs

And that’s probably it for Vulgus!

November 6, 2023 Retro Ports

I’ve decided to put Vulgus to bed. After a fruitless session, I’ve exhausted my interest in finishing the RE. Given that I don’t have plans to transcode it at all, the ROI for the remining sections is miniscule. The few remaining ‘free-standing’ variables are flags and timers for spawning various …

Blogs

You’ll want to collect ‘E’ as well!

November 5, 2023 Retro Ports

Another session, another few variables decoded (RE’d). Most of the ‘free standing’ variables have either been decoded, or I have at least some idea of what they do – just not the specifics. A surprising number of seemingly unused variables in the code; initialised but no cross-references to code that …

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Blogs

Parallax Scrolling!?!

November 1, 2023 Retro Ports

Another quickie; cracked a few more variables in the last session which revealed an interesting if subtle detail to the game. I had previously deduced the meaning of one variable to be the amount by which the background had scrolled left/right (dy), so it could be used to update, for …

Blogs

‘S’ is for… nothing!

October 29, 2023 Retro Ports

Just a quick one… still progressing on Vulgus, chipping away at the unknown variables. Indications are that the letter ‘S’ does… ABSOLUTELY NOTHING! I can’t find any cross-references to it in the code, other than initialisation and updating a counter (max=4) when one disappears off-screen. A watchpoint in the MAME …

Blogs

It’s official, collecting the letter ‘D’ is good!

October 23, 2023 Retro Ports

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, …

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Blogs

Slowly taking shape

October 7, 2023 Retro Ports

I’ve reached the point in the RE where the rate of progress is beginning to slow. On the bright side, I’ve probably commented about 75% of the code thus far, so I have a good idea of how it’s all working, if not some of the finer details. What’s remaining …

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Blogs

Answers and Questions

October 4, 2023 Retro Ports

More progress tonight and more questions than answers. I started looking at the ‘object’ data structure used in so much of the code. Byte $00 appears to be the state, and $01-$04 appears to be the (16-bit) object X and Y coordinates. The MSB of the coordinates are copied to …

Blogs

Holiday project – Vulgus RE

September 23, 2023 Retro Ports

Long time no post! Truth is I haven’t had the time or the motivation to work on any Retroports projects for the last few months as work and Real Life have both ramped up significantly. The good news is that although work has been a lot busier, I have been …

Blogs

Galaxian star field

June 1, 2023 Retro Ports

I’ve been chipping away at Galaxian as updates come from jotd. It’s all-but-finished now, with a few sounds to implement and/or debug on the Neo Geo, and the mystery of randomly disappearing bombs. I’ve just finished implementing the starfield, although I realise now I made one mistake that I may …