The same apply to you: do not ask for a msx2+ because you have only a msx2+
These are the tests I made some weeks earlier, of scroll on SC5 and SC8:
SCREEN 5 (not complete level, but is enought)
https://webmsx.org/?ROM=https://github.com/albs-br/msx-tests...
SCREEN 8 complete
https://webmsx.org/?ROM=https://github.com/albs-br/msx-tests/raw/master/vertical-scroll-screen8.rom&ROM_FORMAT=ASCII16
HUGE difference between SCREEN 5/8 and SCREEN 11. It doesn’t look the same game. Keep it MSX2+ or higher.
Screen 5 looks better than Screen 8 and allows palette effects. More than enough for a great game (see Aleste saga as proof).
Screen 5 looks better than Screen 8 and allows palette effects. More than enough for a great game (see Aleste saga as proof).
There's quite a number of games in screen 5, let it be in screen 11 because we miss those 
I'm sure the screen 8 graphics can be better using the proper converter tool and correct options.
What you mean by "proper conversion tools"? All conversions were done by the same tool (BMP2MSX).
On the other hand, nobody is saying that you should go for the MSX2 version only, both are feasible in my opinion. Screen 8 and screen 11 use the same resolution, I'm not a coder but changes should be few.
Yes, for screen 8 the changes in scroll algorithm would be few or none. BUT, the changes on sprites will be enormous, as the OR colors must be all recalculated (and the palette is ugly and fixed, as stated before).
For screen 5 the probçems are others: I can use a precompile directive to switch the INCLUDE files of images, and some constants (line size in bytes for example), and change MegaROM mapper type from ASCII16 to ASCII8 (so I don't have to change the scroll algorithm). BUT, the palette of the bg and the sprites are the same, and that is a tremendous limitation.
Of course the final result would be better with the V9958, for sure (and i will be surprised if not), but both the screen 5 / 8 versions looks decent considering the limitations of the screen modes you use.
I can understand if you want to make a V9958 exclusive title, but blaming the "sc5" and "sc8" video modes as the only reason to not support a "less appealing" version sounds like a pretext to me.
For me the actual feasibility depends on the final result. If the result is decent it can be done. Of course with the V9958 the result is better, but following this reasoning why not program a version for the v9990? The result will be even better.
I've always been the first to be critical of those asking for versions of games for MSX1 when they were only (at least) decently feasible only for MSX2 or higher, but here the situation is different. The version for the V9938 is less beautiful but still decent.
This game has no peculiarities that make it impossible to implement on V9938 such as fast horizontal scrolling. Justifying the version for the V9958 only with the motivation of the greatest number of colors available at the same time or the colors of the sprites definitely sounds like a weak motivation from a technical point of view.
It is different if the motivation is: "I want something exclusive to MSX2 +", which is not a technical motivation but a personal one.
I don’t agree that there is no technical motivation, and I think it’s a bit unfair to say so. I think there is a collective trauma among MSX users about smooth scrolling, such that as soon as something can scroll on V9938 it must be done, no matter the sacrifices, to prove MSX2 is worthy. But the colourfulness and graphic appeal you would lose is just as important a part of a game.
I think albs_br’s explanation of the issues with sprites and colours are clear… The two tests just show a scrolling background, it’s only a part of the picture. Of course it is possible to make a version for V9938. But it will look worse and involve a lot of extra work. That to me is a clear and technical motivation and a fair reason not to do it.
Of course the final result would be better with the V9958, for sure (and i will be surprised if not), but both the screen 5 / 8 versions looks decent considering the limitations of the screen modes you use.
I can understand if you want to make a V9958 exclusive title, but blaming the "sc5" and "sc8" video modes as the only reason to not support a "less appealing" version sounds like a pretext to me.
For me the actual feasibility depends on the final result. If the result is decent it can be done. Of course with the V9958 the result is better, but following this reasoning why not program a version for the v9990? The result will be even better.
I've always been the first to be critical of those asking for versions of games for MSX1 when they were only (at least) decently feasible only for MSX2 or higher, but here the situation is different. The version for the V9938 is less beautiful but still decent.
This game has no peculiarities that make it impossible to implement on V9938 such as fast horizontal scrolling. Justifying the version for the V9958 only with the motivation of the greatest number of colors available at the same time or the colors of the sprites definitely sounds like a weak motivation from a technical point of view.
It is different if the motivation is: "I want something exclusive to MSX2 +", which is not a technical motivation but a personal one.
Why cant someone go for the more appealing version? otherwise you can say you shouldnt use opll/psg/opl4 because you can make a "stil decent" sounding PSG soundtrack.
Imho just let the coder do as he wish, it's his project, his fun, his decision.
. Of course it is possible to make a version for V9938. But it will look worse and involve a lot of extra work
So go to develop a V9990 version. Of course it could be made with a V9958, but it will look worse and involve a lot (not so sure how much lot) of extra work.
These are the tests I made some weeks earlier, of scroll on SC5 and SC8:
SCREEN 5 (not complete level, but is enought)
https://webmsx.org/?ROM=https://github.com/albs-br/msx-tests...
SCREEN 8 complete
https://webmsx.org/?ROM=https://github.com/albs-br/msx-tests/raw/master/vertical-scroll-screen8.rom&ROM_FORMAT=ASCII16
HUGE difference between SCREEN 5/8 and SCREEN 11. It doesn’t look the same game. Keep it MSX2+ or higher.
Actually, the background pictures were converted WITHOUT regarding to the sprite colors. With these limitations the result would be even worse. Some picture treatment before the conversion is needed, as someone suggested earlier.