Screen 4 wasn’t unused...
Space Manbow, Psycho World, Higemaru, Hydefos, Golvellius 2, Giana Sisters...
Coincidentally all games that scroll horizontally 
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Being very curious about SOTB demo, I'd like to understand whether it's possible to:
1. create a full game? Does it have to be in the cartridge (like PoP for C64) or can be loaded/overlayed from the floppy?
2. is it possible to sustain the sampled sound? Personally, the SOTB sound adaptation in the demo is amazing... On the stock hardware. The sound is as important as good graphics in SOTB.
The SOTB one-screen is for GX4000 (i.e. requires only 64kb ram) and thus is on a cartridge - forget floppy here and 128kb ram would not be enough (for samples and generated data/code). Read my words back on Pouet: this is a demo and not a POC for a game. A game with such quality (on sound and parallax scrollings) is not possible.
You got it! main achievement here is the sound in the stock hardware i.e. feeling like 4-voices MOD but thru AY = 3-voices logarithmic square-signal generator. It fills 368kb (out of 512) from the cartridge. Well! a fairly acceptable 3-voices MOD with no fancy on sound would require much less (80-100kb). I can't think about a game using so much data for one song only. Also: I can't think about a game spending 30% of its cputime managing sound - instead of taking care of screen first.
3. when running on MSX2+ would it be possible to achieve the comparable parallax performance on the main level?
Definitely: yes it could.
Note: not the sound, just the parallax (easy!) and the layers (with some demo-tricks as I did). I quote myself: just missing some motivated guys to turn that "it could" into "yes we did it!"
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Quick question about the CPCPlus SOTB screen, how are those multiple layers achieved? Does the CPC plus support multiple layers or is it using the hardware sprites capabilities?
Amstrad plus and GX4000 do not have multiple layers - do not have text mode (i.e. main screen from SOTB here is bitmap only - its size would be 16kb).
Let's make it simple. First about parallax.
Main screen is virtually twice larger. Then thanks to interruptions and horizontal hardware scroll: horizontal slices of the screen are scrolling. 40+ interruptions were required.
Then about layers.
It's a mix of:
1) hardware upscaled sprites for the foreground = beast + tree or whatever
2) software sprites for moon and aircrafts
3) pre-shifted texture for grass behind bottom wall/barrier
Some details
1) Hardware sprites here are used in a standard way: no multiplexing, no cheat anywhere
2) Software sprites: on that part of screen, it's @25Hz not 50Hz. Then? well, you guess it: some generated code (32Ko) to be fast - using some reversed mask table: not "in front" (of clouds) but "behind" (the clouds).
3) Look at 2nd screen which displays the grass texture (wall+barrier were removed): you see? it's 7 pixels width only. For that small part of the screen, there are 7 versions of wall+barrier - each gets the grass texture shifted by one-pixel. Which allows to animate thru these 7 versions (16kb vram if you ask).
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Returning to the origin of the thread, I must say that this demo is really impressive, Amstrad CPC plus seems to be a very capable and underused machine.
That's it! exactly what I wanted to show - with a demo.
Others have same goal - with a game (and what a game!)
I saw it live and this "Ghosts'n Goblins" kicks ass(es)! to be released this year.
Watch it in action.
Screen 4 wasn’t unused...
Space Manbow, Psycho World, Higemaru, Hydefos, Golvellius 2, Giana Sisters...
Coincidentally all games that scroll horizontally .
Wow, Golvellius 2 (and effectively Super Cooks) as well? I never knew that. Wouldn't have guessed, even. But it makes sense considering the horizontally scrolling dungeons.
That does look amazing indeed! I really start to like the graphics of the advanced Amstrads
