Jetboat Disassembly

reminisce about classic bbc micro and acorn electron games here
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melchett
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Jetboat Disassembly

Post by melchett »

What started out as a simple "why does the boat continually judder on my real BBC B", subsequently crafting a fix for that and the Master Compact, then progressed into a full diassembly of the code. It's been quite an education going though Jetboat and, luckily for me, it's well structured and thought through by the author. Which made discovering how it worked a little easier for my first full disassembly and attempt at commenting.

The disassembly is there to educate me and the labelling/commenting style may not be to everyone's taste. It will NOT compile on real hardware (not my goal) but it does compile using beebasm and generate a then usable SSD image.

I was curious about the game too as it's quite difficult so what did it offer beyond the few laps that I can get through. I wrote some code to generate the maps for each level and the different colour schemes too. It is a nice game and could be lifted and converted to the Electron I guess - seem to remember 0xCODE asking that question. There is some MODE7 in it but could easily be changed to another mode. It uses hardware scrolling too which I think would have to change?

The main repository is in github and displays the README.md obviously by default. Instructions on how to build it are also contained on that page. The disassembly is based on the version I had on cassette as a child and I note that the one in bbcmicro.co.uk separates the relocation code from the main game code so it's pretty much the same overall.

The README.md contains the images of each lap which have progressively more hazards per stage. Each new stage changes the palette and also reduces the time to complete each lap in the stage until it's impossible. I have summarised and commented each section of code in the in the main jetboat-commented.asm file.

It was something to do during the long dark evenings of lockdown at least! Hopefully someone else will find some use from this too.

Andy
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Diminished
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Re: Jetboat Disassembly

Post by Diminished »

Nicely done! Love seeing another title disassembled.

Maybe make a post over here so it can be added to the list.
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TobyLobster
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Re: Jetboat Disassembly

Post by TobyLobster »

Diminished wrote:
Wed Sep 08, 2021 4:38 pm
Maybe make a post over here so it can be added to the list.
Added. There's quite a few disassemblies listed there now.
Nice work on the disassembly.
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0xC0DE
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Re: Jetboat Disassembly

Post by 0xC0DE »

Excellent work! =D>
I never have the patience to write so many comments in a disassembly :mrgreen:

It could definitely work on an Electron. The screen scrolling is the only 'problem' which can be solved by a fast unrolled software scroll routine and/or by making the play window smaller.
0xC0DE
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MarkMoxon
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Re: Jetboat Disassembly

Post by MarkMoxon »

That’s a great disassembly! Such detailed comments - you can never have too many of those.

An excellent job, thanks for sharing it! =D>

Mark
melchett
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Re: Jetboat Disassembly

Post by melchett »

Thank you Mark, Toby, Diminished and 0xCODE for the kind comments!
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Dave Footitt
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Re: Jetboat Disassembly

Post by Dave Footitt »

Great job =D>

Jetboat was one of the first games I had on my Beeb and I spent many hours on it, with fond memories!
melchett
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Re: Jetboat Disassembly

Post by melchett »

Dave Footitt wrote:
Sun Sep 12, 2021 7:38 pm
Great job =D>

Jetboat was one of the first games I had on my Beeb and I spent many hours on it, with fond memories!
Thank you Dave - all the feedback here is appreciated. How far do you remember getting - having played this to death (with cheats) I'm curious to know what a real dedicated player could achieve? It's an exponentially tough game.
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