The Plus range of computers is interesting - the cartridges provide 512KB of data, and the systems have a minimum of 64KB of memory. Sure, 16KB is used up by the display, but that leaves quite a bit of space for the dynamic data the game engine will require. However, this is not a contiguous memory space - there is a primitive memory mapping system that I will have to get to grips with, and the 16KB page size will drive some of engine design.
My general plan is to have a game engine that fits entirely within 16KB of ROM, so it can be paged in once. The screen is another 16KB. There will be various tables of dynamic data in the game (object instances, flags, counters, NPC dynamic data, etc) - this will have to reside in RAM. However the fixed data backing these up will live on the ROM, and be paged in as required for scoring, UI, etc.
As for the game world, I am currently envisioning a set of maps, linked by portals (okay, doors), covering standard fantasy fare - a city, a castle, a wilderness, a desert, mountains, inns, caves, etc.
The representation, at least on the CPC, will be an overhead 2D graphical view. The Plus range has a decent 16-colour chunky graphics mode where I can pick from 4096 colours, and 16, 16-colour sprites with their own palette. The sprites have their limitations (not easy to animate), but should be more than enough for this game.
My current plan is for a map to be up-to 8x8 screens in size, and a screen to be composed of 9x7 'super-blocks', which themselves are 4x4 character cells in size. This means the view will be full screen, on a 36x28 display (did I mention that the CRTC chip inside the CPC range of computers is very programmable - a C64 version would target 10x8). The idea is that this will save lots of memory without affecting the game too much, especially if the player isn't limited to tile by tile movement.
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