Doodlebug Remastered

Doodlebug is one of the latter games released by Mastertronic for the Vic20 during their 8-bit days. What I've done here is used Claude to both reverse engineer the original .prg binary and convert into commented Kick Assembler source  and then assist me into fixing a few bugs, removing old cracker watermarks and introducing as many new features as possible into the original 3.5k game without changing the core gameplay loop. 

Not that there was much of it, but Ikari thought it was worth cracking back in the day, it seems. I also happen to concede that it was one of my more favoured games during my teenage Vic20 years and I've often found myself tinkering with it and reusing the character set alphabet, for example.

Anyway, enough of that. What's actually been changed here to justify putting a modified version on Itch?

Doodlebug originally only had one maze screen to play on, and this was actually stored in memory as it was displayed so it took up almost 0.5 of a kilobyte from the 3.5k an unexpanded Vic has for game space. The file itself was originally a cracked game, it turns out, so I dumped out the disassembly from a vice snapshot file so the original game could be preserved to start from.

When I loaded the source code file and built it with Dev20 it turned out to have only 1 byte free in memory. Fortunately a thorough scan showed the map usage and a few other bits of code that were either not required or were left over debris that was never accessed by the game itself.

So, here's the new features in the game. Still for the unexpanded Vic20:

Three mazes - two of them are brand new, plus the original.

New music on title screen and game over screens (yes, it has that now).

Level number display.

Game Over screen.

Bug fixes to the level and enemies selection counters on the title screen, and some code that broke Vice joystick emulation but wouldn't have affected the original game. There was also an issue with the bomb placement which now works better. 

Gameplay:

Eat every dot in the maze. Clear the maze to go to the next level (the three mazes take turns). You get 5 lives and 5 bombs, and one extra bomb (max 9) for each cleared level. A spray cloud kills any devil that walks into it (+100 points) but it is dangerous to you as well.

You can use the gates to trap aliens from killing you by pushing through either side.

Legal mumbo jumbo:

I don't own this game. Well, I do own an original cassette tape, but that's not the point. I never wrote the original game for Mastertronic and I likely have zero rights to do any of what I've done here by reverse engineering and reworking from that disassembly but I'm quietly optimistic that nobody is going to care any more. 

This game hasn't been commercially available for sale in over 40 years now, just like the Vic 20 computer itself. So, Mastertronic - if they even still existed - have not made any money from it in a long, long time. I intend to do exactly the same. 

This game is listed for download as free. I don't have the right to sell it and wouldn't even attempt that. If I'm asked by someone who does own the intellectual property and wants it taken down then that's going to happen. Pretty unlikely, however.

I will be posting the source code up on my github public repositories: https://github.com/LordXerra for anyone who wants to look at the revised source code. I'm not putting up the original disassembly in case that's going too far. It's buggy anyway, remember :)