Mark Moxon
@markmoxon.bsky.social
Writer, walker, software archaeologist. Back in the day: Editor of Acorn User, Editor of h2g2.
I love analysing old code, and my aim is to create the best code disassemblies you have ever seen.
Purveyor of Elite/Lander/Revs hacks.
www.markmoxon.com
I love analysing old code, and my aim is to create the best code disassemblies you have ever seen.
Purveyor of Elite/Lander/Revs hacks.
www.markmoxon.com
I've started writing a series of deep dives into Geoff Crammond's epic #BBCMicro game The Sentinel.
Here's the to-do list.
I will post a link here whenever I add a new one to thesentinel.bbcelite.com
It's going to take a while! But it should be worth it...
#retrocomputing #retrogaming #c64 #8bit
Here's the to-do list.
I will post a link here whenever I add a new one to thesentinel.bbcelite.com
It's going to take a while! But it should be worth it...
#retrocomputing #retrogaming #c64 #8bit
January 31, 2026 at 3:56 PM
I've started writing a series of deep dives into Geoff Crammond's epic #BBCMicro game The Sentinel.
Here's the to-do list.
I will post a link here whenever I add a new one to thesentinel.bbcelite.com
It's going to take a while! But it should be worth it...
#retrocomputing #retrogaming #c64 #8bit
Here's the to-do list.
I will post a link here whenever I add a new one to thesentinel.bbcelite.com
It's going to take a while! But it should be worth it...
#retrocomputing #retrogaming #c64 #8bit
You didn't know you needed this in your life, but you do.
Marine Beaufils is a French artist who creates beautiful embroideries of... The Sentinel (amongst others).
It's inspired and quite beautiful. Enjoy!
www.marine.st/en/pages/sen...
#bbcmicro #zxspectrum #c64 #retrogaming #retrocomputing
Marine Beaufils is a French artist who creates beautiful embroideries of... The Sentinel (amongst others).
It's inspired and quite beautiful. Enjoy!
www.marine.st/en/pages/sen...
#bbcmicro #zxspectrum #c64 #retrogaming #retrocomputing
January 13, 2026 at 11:42 AM
You didn't know you needed this in your life, but you do.
Marine Beaufils is a French artist who creates beautiful embroideries of... The Sentinel (amongst others).
It's inspired and quite beautiful. Enjoy!
www.marine.st/en/pages/sen...
#bbcmicro #zxspectrum #c64 #retrogaming #retrocomputing
Marine Beaufils is a French artist who creates beautiful embroideries of... The Sentinel (amongst others).
It's inspired and quite beautiful. Enjoy!
www.marine.st/en/pages/sen...
#bbcmicro #zxspectrum #c64 #retrogaming #retrocomputing
And here's the game's opening screen, for reference.
January 10, 2026 at 5:20 PM
And here's the game's opening screen, for reference.
Have you ever wondered how big the full landscape is in The Sentinel?
It's 1856 pixels high and 2048 pixels wide.
Here's the first level. The initial 192x160 screen is in red. Panning jumps the view to different grid points.
It's a big old world!
#retrocomputing #retrogaming #bbcmicro #c64 #8bit
It's 1856 pixels high and 2048 pixels wide.
Here's the first level. The initial 192x160 screen is in red. Panning jumps the view to different grid points.
It's a big old world!
#retrocomputing #retrogaming #bbcmicro #c64 #8bit
January 10, 2026 at 5:10 PM
Have you ever wondered how big the full landscape is in The Sentinel?
It's 1856 pixels high and 2048 pixels wide.
Here's the first level. The initial 192x160 screen is in red. Panning jumps the view to different grid points.
It's a big old world!
#retrocomputing #retrogaming #bbcmicro #c64 #8bit
It's 1856 pixels high and 2048 pixels wide.
Here's the first level. The initial 192x160 screen is in red. Panning jumps the view to different grid points.
It's a big old world!
#retrocomputing #retrogaming #bbcmicro #c64 #8bit
I've also been keeping a detailed development diary during this project.
Before I tackled my first disassembly, I couldn't fathom how people did it. It felt like arcane magic.
So I've written down every single step in the journey from game binary to finished project.
I'll publish it soon.
8/9
Before I tackled my first disassembly, I couldn't fathom how people did it. It felt like arcane magic.
So I've written down every single step in the journey from game binary to finished project.
I'll publish it soon.
8/9
January 2, 2026 at 4:29 PM
I've also been keeping a detailed development diary during this project.
Before I tackled my first disassembly, I couldn't fathom how people did it. It felt like arcane magic.
So I've written down every single step in the journey from game binary to finished project.
I'll publish it soon.
8/9
Before I tackled my first disassembly, I couldn't fathom how people did it. It felt like arcane magic.
So I've written down every single step in the journey from game binary to finished project.
I'll publish it soon.
8/9
The plan is the same as with all my disassembly projects.
First, release the repository. That’s done!
Next, release a website version of the commented code.
Then write lots of deep dives into how the game works. I have a long list.
And then I hope to add the #Commodore64 version to the mix.
7/9
First, release the repository. That’s done!
Next, release a website version of the commented code.
Then write lots of deep dives into how the game works. I have a long list.
And then I hope to add the #Commodore64 version to the mix.
7/9
January 2, 2026 at 4:29 PM
The plan is the same as with all my disassembly projects.
First, release the repository. That’s done!
Next, release a website version of the commented code.
Then write lots of deep dives into how the game works. I have a long list.
And then I hope to add the #Commodore64 version to the mix.
7/9
First, release the repository. That’s done!
Next, release a website version of the commented code.
Then write lots of deep dives into how the game works. I have a long list.
And then I hope to add the #Commodore64 version to the mix.
7/9
But there’s plenty of beauty and wonder to see.
At this stage the overall picture is hard to fathom, but poking through the source is a delightful way to appreciate the brilliance of Geoff Crammond’s code.
Scroll through. Take a look at random parts of the source. See how it works. Enjoy!
6/9
At this stage the overall picture is hard to fathom, but poking through the source is a delightful way to appreciate the brilliance of Geoff Crammond’s code.
Scroll through. Take a look at random parts of the source. See how it works. Enjoy!
6/9
January 2, 2026 at 4:29 PM
But there’s plenty of beauty and wonder to see.
At this stage the overall picture is hard to fathom, but poking through the source is a delightful way to appreciate the brilliance of Geoff Crammond’s code.
Scroll through. Take a look at random parts of the source. See how it works. Enjoy!
6/9
At this stage the overall picture is hard to fathom, but poking through the source is a delightful way to appreciate the brilliance of Geoff Crammond’s code.
Scroll through. Take a look at random parts of the source. See how it works. Enjoy!
6/9
Note that is a first-release version of the commentary and this project is very much ongoing.
There are errors! There are typos! There are misunderstandings!
It’s a complex beast.
Comments that need improving are marked with "???". I hope to explain these properly over time. We’ll get there.
5/9
There are errors! There are typos! There are misunderstandings!
It’s a complex beast.
Comments that need improving are marked with "???". I hope to explain these properly over time. We’ll get there.
5/9
January 2, 2026 at 4:29 PM
Note that is a first-release version of the commentary and this project is very much ongoing.
There are errors! There are typos! There are misunderstandings!
It’s a complex beast.
Comments that need improving are marked with "???". I hope to explain these properly over time. We’ll get there.
5/9
There are errors! There are typos! There are misunderstandings!
It’s a complex beast.
Comments that need improving are marked with "???". I hope to explain these properly over time. We’ll get there.
5/9
It is hard to describe how impressive this game was back in 1986.
Its design embraces the technical limitations of the hardware to create a uniquely tense experience.
The 3D scrolling landscape is an 8-bit wonder.
It is essentially a VR game, before VR even existed… and all this in just 32K.
4/9
Its design embraces the technical limitations of the hardware to create a uniquely tense experience.
The 3D scrolling landscape is an 8-bit wonder.
It is essentially a VR game, before VR even existed… and all this in just 32K.
4/9
January 2, 2026 at 4:29 PM
It is hard to describe how impressive this game was back in 1986.
Its design embraces the technical limitations of the hardware to create a uniquely tense experience.
The 3D scrolling landscape is an 8-bit wonder.
It is essentially a VR game, before VR even existed… and all this in just 32K.
4/9
Its design embraces the technical limitations of the hardware to create a uniquely tense experience.
The 3D scrolling landscape is an 8-bit wonder.
It is essentially a VR game, before VR even existed… and all this in just 32K.
4/9
I have documented the #BBCMicro version of the game to start with, and I hope to add the #Commodore64 version later.
On both platforms The Sentinel is a stone-cold classic.
It boasts filled 3D graphics, eerie silences, utterly unique gameplay and an atmosphere you can cut with a knife.
3/9
On both platforms The Sentinel is a stone-cold classic.
It boasts filled 3D graphics, eerie silences, utterly unique gameplay and an atmosphere you can cut with a knife.
3/9
January 2, 2026 at 4:29 PM
I have documented the #BBCMicro version of the game to start with, and I hope to add the #Commodore64 version later.
On both platforms The Sentinel is a stone-cold classic.
It boasts filled 3D graphics, eerie silences, utterly unique gameplay and an atmosphere you can cut with a knife.
3/9
On both platforms The Sentinel is a stone-cold classic.
It boasts filled 3D graphics, eerie silences, utterly unique gameplay and an atmosphere you can cut with a knife.
3/9
This project has taken four months (so far!).
The result is more than 40,000 lines of heavily and lovingly commented source code that I reconstructed from a disassembly of the original BBC Micro game binaries.
Want to cut to the chase? Here’s the main source file:
github.com/markmoxon/th...
2/9
The result is more than 40,000 lines of heavily and lovingly commented source code that I reconstructed from a disassembly of the original BBC Micro game binaries.
Want to cut to the chase? Here’s the main source file:
github.com/markmoxon/th...
2/9
January 2, 2026 at 4:29 PM
This project has taken four months (so far!).
The result is more than 40,000 lines of heavily and lovingly commented source code that I reconstructed from a disassembly of the original BBC Micro game binaries.
Want to cut to the chase? Here’s the main source file:
github.com/markmoxon/th...
2/9
The result is more than 40,000 lines of heavily and lovingly commented source code that I reconstructed from a disassembly of the original BBC Micro game binaries.
Want to cut to the chase? Here’s the main source file:
github.com/markmoxon/th...
2/9
I'm hoping to release my latest ultra-comprehensive gold-standard 6502 disassembly in the next few days.
It's been four months in the making and is almost complete.
Elite, Aviator, Revs, Lander… and now this.
Let the countdown begin: 🤖🪨🌲
#retrocomputing #retrogaming #bbcmicro #commodore64 #8bit
It's been four months in the making and is almost complete.
Elite, Aviator, Revs, Lander… and now this.
Let the countdown begin: 🤖🪨🌲
#retrocomputing #retrogaming #bbcmicro #commodore64 #8bit
December 29, 2025 at 7:08 PM
I'm hoping to release my latest ultra-comprehensive gold-standard 6502 disassembly in the next few days.
It's been four months in the making and is almost complete.
Elite, Aviator, Revs, Lander… and now this.
Let the countdown begin: 🤖🪨🌲
#retrocomputing #retrogaming #bbcmicro #commodore64 #8bit
It's been four months in the making and is almost complete.
Elite, Aviator, Revs, Lander… and now this.
Let the countdown begin: 🤖🪨🌲
#retrocomputing #retrogaming #bbcmicro #commodore64 #8bit
Some projects just take a long time to work through. I mean, I’ve got to make sure it can stand alongside the others.
It should be worth the wait, though.
#8bit #bbcmicro #disassembly
It should be worth the wait, though.
#8bit #bbcmicro #disassembly
November 19, 2025 at 7:26 PM
Some projects just take a long time to work through. I mean, I’ve got to make sure it can stand alongside the others.
It should be worth the wait, though.
#8bit #bbcmicro #disassembly
It should be worth the wait, though.
#8bit #bbcmicro #disassembly
Here’s an example - the iconic box art from the BBC Micro version, brought to life in-game.
And there’s a Commodore 64 version too. You can even swap files between the two, so you can create a scene on a Beeb, save it and play it on a C64.
I really enjoyed building this one, I have to say!
And there’s a Commodore 64 version too. You can even swap files between the two, so you can create a scene on a Beeb, save it and play it on a C64.
I really enjoyed building this one, I have to say!
November 5, 2025 at 9:13 PM
Here’s an example - the iconic box art from the BBC Micro version, brought to life in-game.
And there’s a Commodore 64 version too. You can even swap files between the two, so you can create a scene on a Beeb, save it and play it on a C64.
I really enjoyed building this one, I have to say!
And there’s a Commodore 64 version too. You can even swap files between the two, so you can create a scene on a Beeb, save it and play it on a C64.
I really enjoyed building this one, I have to say!
I've finally finished pimping my David Braben-signed BBC Micro B+, and it can now run more variants of Bell & Braben Elite than any other contemporary machine ever.
The #BBCMicro B+ is officially the Commander-in-Chief of #8bit #Elite. 🫡
See thread for details.
(1/8)
#retrogaming #retrocomputing
The #BBCMicro B+ is officially the Commander-in-Chief of #8bit #Elite. 🫡
See thread for details.
(1/8)
#retrogaming #retrocomputing
November 5, 2025 at 7:42 PM
I've finally finished pimping my David Braben-signed BBC Micro B+, and it can now run more variants of Bell & Braben Elite than any other contemporary machine ever.
The #BBCMicro B+ is officially the Commander-in-Chief of #8bit #Elite. 🫡
See thread for details.
(1/8)
#retrogaming #retrocomputing
The #BBCMicro B+ is officially the Commander-in-Chief of #8bit #Elite. 🫡
See thread for details.
(1/8)
#retrogaming #retrocomputing
The other one might be LK18? If so, it controls whether banks 4 and 5 contain sideways RAM or the two banks in a 32K ROM fitted into IC41. West indicates sideways RAM, which is the shippd position, so this one is also correct, I think?
October 16, 2025 at 1:15 PM
The other one might be LK18? If so, it controls whether banks 4 and 5 contain sideways RAM or the two banks in a 32K ROM fitted into IC41. West indicates sideways RAM, which is the shippd position, so this one is also correct, I think?
I can't tell what the link number for the top one is, the picture is a bit faded. Can you tell which one it is?
The bottom one looks like LK12, which is in position B in shipped Masters (according to the Advanced Master Reference Guide).
The bottom one looks like LK12, which is in position B in shipped Masters (according to the Advanced Master Reference Guide).
October 16, 2025 at 1:10 PM
I can't tell what the link number for the top one is, the picture is a bit faded. Can you tell which one it is?
The bottom one looks like LK12, which is in position B in shipped Masters (according to the Advanced Master Reference Guide).
The bottom one looks like LK12, which is in position B in shipped Masters (according to the Advanced Master Reference Guide).
I'm pleased to announce the #Elite Compendium for the #Acorn #Electron, containing three amazing hacked versions of Elite on one disc.
It includes a brand new version: musical Elite. On the Electron!
Lots of details here: elite.bbcelite.com/hacks/elite_...
#retrogaming #retrocomputing #bbcmicro
It includes a brand new version: musical Elite. On the Electron!
Lots of details here: elite.bbcelite.com/hacks/elite_...
#retrogaming #retrocomputing #bbcmicro
August 20, 2025 at 12:26 PM
I'm pleased to announce the #Elite Compendium for the #Acorn #Electron, containing three amazing hacked versions of Elite on one disc.
It includes a brand new version: musical Elite. On the Electron!
Lots of details here: elite.bbcelite.com/hacks/elite_...
#retrogaming #retrocomputing #bbcmicro
It includes a brand new version: musical Elite. On the Electron!
Lots of details here: elite.bbcelite.com/hacks/elite_...
#retrogaming #retrocomputing #bbcmicro
The incomparable @negativecharge.bsky.social recently converted the Commodore 64 Elite music to the Electron.
I've finally found time to add it to Electron Elite.
Here's the docking computer in all its one-channel glory.
Turn your sound on!
#retrocomputing #retrogaming #electron #bbcmicro #8bit
I've finally found time to add it to Electron Elite.
Here's the docking computer in all its one-channel glory.
Turn your sound on!
#retrocomputing #retrogaming #electron #bbcmicro #8bit
August 13, 2025 at 1:08 PM
The incomparable @negativecharge.bsky.social recently converted the Commodore 64 Elite music to the Electron.
I've finally found time to add it to Electron Elite.
Here's the docking computer in all its one-channel glory.
Turn your sound on!
#retrocomputing #retrogaming #electron #bbcmicro #8bit
I've finally found time to add it to Electron Elite.
Here's the docking computer in all its one-channel glory.
Turn your sound on!
#retrocomputing #retrogaming #electron #bbcmicro #8bit
Look at this little beauty! It's my new BBC Micro B+, signed by David Braben himself, and it’s the inspiration for my latest project:
"BBC Master Elite, backported to run on the unexpanded B+, and with lots of extra features"
Links in thread.
#retrocomputing #retrogaming #bbcmicro #8bit #elite
"BBC Master Elite, backported to run on the unexpanded B+, and with lots of extra features"
Links in thread.
#retrocomputing #retrogaming #bbcmicro #8bit #elite
August 6, 2025 at 12:12 PM
Look at this little beauty! It's my new BBC Micro B+, signed by David Braben himself, and it’s the inspiration for my latest project:
"BBC Master Elite, backported to run on the unexpanded B+, and with lots of extra features"
Links in thread.
#retrocomputing #retrogaming #bbcmicro #8bit #elite
"BBC Master Elite, backported to run on the unexpanded B+, and with lots of extra features"
Links in thread.
#retrocomputing #retrogaming #bbcmicro #8bit #elite
My new project is a version of BBC Master Elite, but with a twist.
Sure, it’s pretty niche, but this has never been done before, which is always fun.
Can you tell what it is yet? The clue's in the clip...
#retrocomputing #retrogaming #bbcmicro #8bit #elite
Sure, it’s pretty niche, but this has never been done before, which is always fun.
Can you tell what it is yet? The clue's in the clip...
#retrocomputing #retrogaming #bbcmicro #8bit #elite
July 25, 2025 at 1:34 PM
My new project is a version of BBC Master Elite, but with a twist.
Sure, it’s pretty niche, but this has never been done before, which is always fun.
Can you tell what it is yet? The clue's in the clip...
#retrocomputing #retrogaming #bbcmicro #8bit #elite
Sure, it’s pretty niche, but this has never been done before, which is always fun.
Can you tell what it is yet? The clue's in the clip...
#retrocomputing #retrogaming #bbcmicro #8bit #elite
It's done! I have just released the Compendium version of #Elite for the #Acorn #Electron.
This massively enhanced version of the original game contains pretty much every feature of #BBCMicro Elite, but on the Electron. Just add 16K of sideways RAM.
Links in thread.
#retrocomputing #retrogaming
This massively enhanced version of the original game contains pretty much every feature of #BBCMicro Elite, but on the Electron. Just add 16K of sideways RAM.
Links in thread.
#retrocomputing #retrogaming
July 10, 2025 at 3:58 PM
It's done! I have just released the Compendium version of #Elite for the #Acorn #Electron.
This massively enhanced version of the original game contains pretty much every feature of #BBCMicro Elite, but on the Electron. Just add 16K of sideways RAM.
Links in thread.
#retrocomputing #retrogaming
This massively enhanced version of the original game contains pretty much every feature of #BBCMicro Elite, but on the Electron. Just add 16K of sideways RAM.
Links in thread.
#retrocomputing #retrogaming
Today's addition to #Acorn #Electron #Elite is the energy bomb animation from the Apple II, BBC Master and NES.
In the original Electron version, the energy bomb did little more than beep gently. Now it rages with lightning bolts! That's much better.
#retrogaming #retrocomputing #8bit #bbcmicro
In the original Electron version, the energy bomb did little more than beep gently. Now it rages with lightning bolts! That's much better.
#retrogaming #retrocomputing #8bit #bbcmicro
July 6, 2025 at 1:01 PM
Today's addition to #Acorn #Electron #Elite is the energy bomb animation from the Apple II, BBC Master and NES.
In the original Electron version, the energy bomb did little more than beep gently. Now it rages with lightning bolts! That's much better.
#retrogaming #retrocomputing #8bit #bbcmicro
In the original Electron version, the energy bomb did little more than beep gently. Now it rages with lightning bolts! That's much better.
#retrogaming #retrocomputing #8bit #bbcmicro
The Compendium version of #Acorn #Electron #Elite now has missions - three of them, in fact.
Here's the briefing for the Constrictor mission, backported from the #BBCMicro; I've also ported the Thargoid plans mission, and the Trumbles from the #C64 and #NES. 🫡
#retrocomputing #retrogaming #8bit
Here's the briefing for the Constrictor mission, backported from the #BBCMicro; I've also ported the Thargoid plans mission, and the Trumbles from the #C64 and #NES. 🫡
#retrocomputing #retrogaming #8bit
July 5, 2025 at 12:26 PM
The Compendium version of #Acorn #Electron #Elite now has missions - three of them, in fact.
Here's the briefing for the Constrictor mission, backported from the #BBCMicro; I've also ported the Thargoid plans mission, and the Trumbles from the #C64 and #NES. 🫡
#retrocomputing #retrogaming #8bit
Here's the briefing for the Constrictor mission, backported from the #BBCMicro; I've also ported the Thargoid plans mission, and the Trumbles from the #C64 and #NES. 🫡
#retrocomputing #retrogaming #8bit
My new version of #Acorn #Electron #Elite is feature-complete! Now for some testing.
Here's the feature list. It’s big! Big enough that this is effectively a Compendium version of Electron Elite; to sit proudly alongside the #BBCMicro Compendia. 🫡
Not long now!
#retrogaming #retrocomputing #8bit
Here's the feature list. It’s big! Big enough that this is effectively a Compendium version of Electron Elite; to sit proudly alongside the #BBCMicro Compendia. 🫡
Not long now!
#retrogaming #retrocomputing #8bit
July 4, 2025 at 6:55 PM
My new version of #Acorn #Electron #Elite is feature-complete! Now for some testing.
Here's the feature list. It’s big! Big enough that this is effectively a Compendium version of Electron Elite; to sit proudly alongside the #BBCMicro Compendia. 🫡
Not long now!
#retrogaming #retrocomputing #8bit
Here's the feature list. It’s big! Big enough that this is effectively a Compendium version of Electron Elite; to sit proudly alongside the #BBCMicro Compendia. 🫡
Not long now!
#retrogaming #retrocomputing #8bit