A downloadable game

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Neutron is a fast-paced vertical shoot-em-up for the Commodore 64 (PAL).

This version was created for RGCD's C64 16KB Cartridge GameDev Compo 2019.

All programming, graphics, and sound by Sarah Jane Avory.

(C) 2019 Protovision.

NB: Although the game has been coded for PAL, it will run quite happily on an NTSC machine, just at a faster speed.


Back in the 80s, after loving playing the arcade game Star Force, I coded my own version on the Commodore 64, one I named Neutron. The game was finished, but never released as Orpheus, the company I was working for at the time, closed down before Neutron could be released…

I still had all the files, but time passed by, and when I moved house many years later, seeing no reason keeping all my old computers, I (rather foolishly looking back now) binned everything, including all my old disks.

Fast forward to the present, and after suffering a bit of burnout while writing lots of novels (I’m also a self-published author), I decided to have a bit of fun and code some C64 games. After coming across the 16Kb cartridge competition, I decided I’d enter that, and thought Neutron would be ideal.

And so I now present Neutron, a re-born version of the game I coded a long time ago. Only this time, with the benefit of lots of coding experience, this game is much improved, in every way.


  • 9 challenging stages of increasing difficulty.
  • Player weapon upgrades.
  • 3 different background styles.
  • Over 18 types of enemies.
  • Mid-stage mini-bosses.
  • End of stage boss.


Joystick in port 2, or Keyboard:

  • S - Up.
  • X - Down.
  • < - Left.
  • > - Right.
  • SPACE - Fire!


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Click download now to get access to the following files:

Neutron.crt (PAL) 16 kB
Neutron.d64 (PAL) 170 kB

Development log


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Excellent game title. Great music and sound effects, graphics and all that. Playing this game reminds me of the classic C64 commercial titles, Fire Track, Denarius, Power Rama, etc. Very addictive and a whole lot of fun crammed into 16KB :) - Amazing :)


A solid little shooter. Fun to play. There are a few bugs (locked up my machine once during an hours worth of play), but still worth playing.


Hi I saw the video of the Neutron game
I am an MSX 1
be possible to port


Neutron is wonderful! I played it on my C64 mini, in Italy the full size TheC64 isn't already available and I'm waiting to purchase it on Amazon.it but I can say that this game is a very very nice vertical shooter, yes! I ask you to code more new games for C64. Bye from Italy and thanx.    P

Why Sarah don't give a short reply to any of the questions for months? Strange.

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I saw V1.3 of this game is already there. Great. I just still miss an option to turn off/on the jerking of the background-objects. This would be highly appreciated (see my former entry below, what exactly i mean).


Brilliant game Sarah, outstanding job.


After playing this for hours, its now one of my favorite SHMUP.


I was gonna test this real quick on my stream the other night, but I couldnt stop playing. Its a great deal of fun, interesting attack waves and good controls. Cant wait to see the full version later on.

Tell all your friends to get this and compete for the highest score - youll have a blast


Excellent game. Well done!


Great games ... thanks for coding :)

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Ciao Derek, I just bought your book and I'm ready for develop :)
I already have some experiences with assembly on C64, but I need to raise the bar!!
Thanks for your work!!!


Amazing game, been blasting away on my C64 emulator today! Great stuff.

Nearly went into the attic to get my old, original  Commodore 64, but it's scary up there!

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Very good game Sarah. Really nice shooter. The explosions for example, looks superb. When this is your first game (?), then hats off. You delivered quality here. One thing i recognized, which wonders me a little bit, so i must ask. When i fly over all the backgrounds in the game (big enemy ships and so on) and don't steer on the joystick, then the scrolling, or better said the background graphics, scrolls very smooth. When i move with my ship around, then i recognized, that the background graphics, for example the big ships over which i fly, have a little jerking. Looks like a very small left/right jerking, like the graphics walk three or five pixels and then back, but it is recognizable as a player. Can this be wiped out in a V1.1 version, or can nothing be done here? Not criticism, just a suggestion for further improvement.


that little movement of the background corresponds to the player's (player moves left -> playfield moves right and vice versa). and it is obviously intended by the author. It gives an illusion of a wider space, or of a certain depth of the games' world.  at least that's what it does make me feel and i'm sure that's what the author wanted to achieve. so IMHO it's a good thing and a feature that should stay in the game.

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Sorry, but i don't understand the sense here. Maybe better, when the programmer itself answers here, cause the question was addressed to her. No attack on you TYREX, but how should a left/right jerking of the background-graphics  give the player an illusion of a wider space or more depth in the game? Then i could also argue, that a non-smooth scrolling in a horizontal "jump and run", brings a wider depth into this game. But how should that be the case? Normally totally smooth scrolling is the goal that programmers want to reach for their games, never heard anything else.

All my retro-gaming-friends and i, perceive this small jerking in "Neutron" as a little bit disturbing. The eyes then goes automatically to the strange jerking objekt and not to the enemies where they normally should be. A totally smooth scrolling gives a better and more realistic feeling, while flying over a landscape or over big enemy spaceships. And this jerking here can also not be designated as something like an earthquake that is happening right now on the ground, because when this would be the case, then the earthquake/jerking would also come, when the player don't move his ship. But it comes only when the player does, so it has something to do with the player and this is the strange and unrealistic thing here. I think, this is not only the meaning of my friends and me.

And furthermore, a version WITH this small jerking already exist now and people who like this, can use this version then. So it would be a good idea, to bring a version now, without the jerking. Then everybody can be satisfied. Don't understand me wrong, i know that the game already is very good and that this maybe is 'complaining' on high comfort level. But especially because i think, that the game is really good, i ask here for further improving it by wiping out that disturbing little jerky left/right background-movement.

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(1 edit)

An ON/OFF option is a great idea. I would be totally in favour. Let's hear what Sarah think about it.


This game is an awesome achievement for 16K! Plays really well, graphics + sounds are excellent for this limited format, as are the controls and the weapons system! Now I'm really looking forward to the full version


If you could make a version for NTSC, I'm on board!  In the meantime, I wish you well with your new release.  It looks really good.


I'll be making a full version in the future (possibly disk but definitely a 512k cartridge), and that will have both PAL and NTSC support.


Fantastic!  I'll be sure to keep a look-out for it!


Please, add hiscore table. An arcade shooter without hiscore, is not complete. :) 

Anyway, Neutron is a great game!

The full version will definitely have a hiscore table, and it'll save it too!


Great news! :) 


Thank you Sarah! :) Nice Game!


Echt gute Arbeit, Sarah! Ich finds richtig gut!

Good work, Sarah! I really enjoy it!


Thank you Sarah!


great little shooter! Had a few goes and third try was my best! Got to stage 3 with a score of 45300.


Well done on your release.


I've been eagerly following the development of this game on Twitter, and bought it the second I saw it was available for sale! One of the best, if not *the* best SHMUP on the system!


It's really good, like a fair take on Lightforce.

Feel bad I didn't pay the asking price now...can I 'buy' it twice? 


Well done! Really nice gameplay.


Really good game!!