CX16 SHMUP engine I am working on

Getafix · Post by **Getafix** » Thu Nov 19, 2020 2:28 am

Hi,

Here's a video that shows the relatively early Shoot 'Em Up Engine I am building for the CX16. In the engine, enemies are scripted, and the enemies are active objects with program counters, stack pointers, local memory, etc. all in a cooperative multi-tasking environment. There's still quite some way to go before I am ready to make an actual game with this, but so far, it's looking really promising. Iteration time for building things is very quick and I love the idea of giving designers, musicians and artists the tools to do what they do (partly because I can't do that stuff ;)

Thank you

Stefan

paulscottrobson · Post by **paulscottrobson** » Thu Nov 19, 2020 8:43 am

I wrote something like that for the BBC Micro 35 years ago, to teach multiprogramming concepts, except it was basically Galaxians (it was a BBC Micro !), though it was much less complicated , more of a script processor than a mini computer. Was great fun though :)

Getafix · Post by **Getafix** » Thu Nov 19, 2020 6:21 pm

9 hours ago, paulscottrobson said:

I wrote something like that for the BBC Micro 35 years ago, to teach multiprogramming concepts, except it was basically Galaxians (it was a BBC Micro !), though it was much less complicated , more of a script processor than a mini computer. Was great fun though ?

I got a BBC Micro not long ago. Other than replace the capacitors to bring it back to life, and a little Basic coding, I haven't done anything with it. I do want to make a game for it though. For some reason there's no cc65 support for the BBC Micro. I was also thinking that working on adding that support may be a good thing. The fact that it doesn't have support does make me wonder if it may be harder than I imagine.

I could easily make this runtime run on the BBC and it's not really tied to SHMUP games. Maybe when the time comes I'll think of something where I can repurpose this for some other 6502 based systems - I want to try and get some game I made on a lot of these. I love learning how they all work. I was astonished at how awesome the Atari 800 is technically, given it came out in 1979! ?

desertfish · Post by **desertfish** » Thu Nov 19, 2020 7:17 pm

I would like to add BBC support to Prog8. However I know next to nothing about that system.... so I won’t be able to properly test it too... don’t even know what the program file format is.

paulscottrobson · Post by **paulscottrobson** » Fri Nov 20, 2020 10:22 am

BBC Micro is a 2Mhz 6502 32k ROM (paged to some extent), 32k RAM. The screen is pixel based with 2/4/16 colour modes. You can scroll vertically in hardware, everything else is byte copying. Sound is an AY-3-8912 (not sure, one of those 3 channel+noise chips)

The real downside as a developer is that the 32k is screen and code RAM, so if you use MODE 5 (160x256x4 colour) you lose about a third, if you use MODE 2 (160x256x16 colour) you lose about 2/3. So for you SHMUP you either have 4 colours or you have 10k RAM for code and data which obviously isn't much.

Very nicely designed and solid, it was well architectured and the software is well thought out in the way that things like the C64 and Spectrum weren't.