There is a review of Moonbase Beta on the Electron User Group site at http://www.acornelectron.co.uk/eug/revs/bbc-games/r-mbet.html There is a slight error on the review, the publisher is credited as Philip Hatton, not Peter Hatton. (Opps) So hopefully someone there will correct the little mistake.
In the mean times you may be interested on some technical information, on some of the code… click on read more!
Sadly one of the source disks (Including the backup) cannot be read, but I can still remember some of the technical bits of the code.
One area of the code was the custom operating system. I didn’t use any OS calls to make the sounds or check the keyboard, so I could se the memory between &0000 (Zero page) and &0400 for my own code. In this area, the code for handling screen time such as the switch from a different colour pallete to another was handled, and also issuing the 50Hz refresh signal. It also generated the sound at 100Hz, and detected the keys being used.
I think the interrupts also controlled the display of the energy bar, so it would flash when it’s low, even during the screen updates.
Why would I use my own OS, one simple reason, speed, but the problem then is the code would not work on the Electron. I didn’t create an Electron version, as I didn’t have access to one. (And I couldn’t afford one either!)
However I did keep in mind what the Electron hardware was capable of, and also from magazines, some information on how to program the Electron hardware, hence the 100Hz sound generator, as if I remember correctly there is a 100Hz interrupt.
So all I had to do was create a new OS source file, compile it, and hope it worked!