Doc Cosmos – GBC Review

Doc Cosmos is a brand new game for the Game Boy Color, made by Simon Jameson, and published by Bitmapsoft. It actually began as a Commodore 64 homebrew game a few years ago, and won an award for game of the year in 2019 from the Commodore 64 fanzine, Freeze 64.

With the success of the C64 version, Simon decided to try turning it into a gameboy game. Doing some research for the game, I found out that he actually streamed the entire development process, so if you’re into homebrew and want to see how it’s made, all the streams are uploaded on his YouTube channel!

So how does this version compare to the original, and is it a good game in its own right, and worth getting a physical release? Let’s find out!

Physical Release

Let’s begin with the packaging, Bitmap soft have done a great job with the materials used for the box. It feels very sturdy, and quite shiny too compared to some other homebrew releases. Unfortunately one problem I had with the box lifts up at the top, almost like it want folded down enough, its only a little gripe though, I really like everything else about it, the print quality is great, and the screenshots on the back look nice and clear too!

Inside the box we have a really nice full colour instruction manual. The manual has great print quality too, and the game cart looks fantastic! I love the colour and the translucent plastic case! This is by far my favourite of all the homebrew carts I’ve seen so far!


Right after the intro sequence you’re dropped off on an alien planet in search of something called the Time Device. After landing on the planet you’ll find a key which opens a door on the other screen, and just after that, the time device! Unfortunately, as he finds it, he’s also gets plunged into a pit and transported back to 1989! The screen goes black and white and as soon as you regain control you notice something is different, suddenly the jump is a lot more restrictive, only allowing you to make the jump, but not control it in the air. This is where the puzzle aspect of the game comes in. You are free to switch between the two different styles, as long as you have power to do so, as indicated but he power meter in the corner here. You can recharge it by going over one of the screens laying around the levels.

I think this is the first GB homebrew game that was programmed in assembly language, rather than GBDK or GB Studio, so I was very curious to see how much more the developer could get out of the system, it turns out, a lot! It’s cool to see a gameboy game be able to shift seamlessly between two versions of a stage like this!

Some areas are only accessible in one form of the other, so you’ll need to experiment with changing the scenes in each area to progress. Some platforms will disappear, some ladders will only show in the past, and certain jumps can only be made in one time period or the other.

The game is also huge! And also extremely difficult! You only have 5 lives, and very few places to get any extras! Also, there’s NO CONTINUES! So no matter how far into the game you get, once it’s a game over, you’re back to the start! There’s also no checkpoints or save feature, so it’s really a game of memorisation… Remember where all the enemies are, remember the death traps and remember how you got to each location using the least amount of time switches to get there! It’s a very very challenging, but ultimately rewarding game!

There’s a few other things that frustrated me as well, for one thing, you can only hold one of each colour key, so when I finally made it to the end of a long series of deadly rooms only to find that the key at the end was the same colour as one I already had, I had to go all the way back again, find a door of that colour so I could use up the key I already had, and then track all the way back through the corridors again to pick it up! Of course, I died on the way and had to start the game all over again! It can also be frustrating if you go far into a stage only to realise you needed just one extra power bar to be able to progress, you’ll have to go all the way back to the nearest power station to recharge and try again! Its all part of the games trial and error deployability though!

There’s several enemies in the game, each with their own predictable movements, they are more like obstacles than enemies as they don’t actually attack you. Some of the hit boxes are a bit too big though I think, especially with the slime that drops from the ceilings, you have to wait for it to disappear completely before you can go past.


Despite my frustration with the game, it’s definitely a very competently programmed homebrew, much better than some others I’ve played! And me not being great at it doesn’t detract from the fact that this is a huge accomplishment for the system! If anyone does decide to play it, please let me know if you manage to finish it! Maybe I’ll revisit it in the future with a fresh mind and try again!

Thanks for reading, Nick (RetroBreak)

Review Score
  • 8/10
    Gameplay - 8/10
  • 7/10
    Graphics - 7/10
  • 9/10
    Sound - 9/10


Despite my frustration with he game, it’s definitely a very competently programmed homebrew, much better than some others I’ve played!


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