I don't know much about Casio hardware, but would it be possible to add grayscale? It would look a lot better than the dithering in those unrevealed tiles.
Well, grayscale is quite the hard thing here.
First, we don't have an ASM community, there are only 2-3 guys who touched sh3 ASM here. So we have to deal with the speed/size loss from programmin in C. Nothing is as optimized as it could be in Axe or z80 ASM. (I'm one of them but I'm still searching a way to code iin ASAM with GCC in Wondws. Do you have a sh3-elf based GCC here with the right tools to compile for Graph family, for Windows?)
Next, in C, having a stable timer-based grayscale has been very hard. We have to deal with a bugged timer and maybe jump limitations. Having a too big addin with grayscale make the calc directly crash. Nothing to debug this.
EDIT :I havee to add that grayscale addins exists, but Graph 35 and 75/85/95 have almost each of oine different reaction to theses addins. The G35+ have for instance a too dark constrast set each time that an addin tries to correct it, and the screen timers are differents for each model...
Third the screen is made to imporve readibilty, it don't have enough "motion-blur"/"afterglow" to have a nice 4-grayscale. Only almost perfect 3 grayscale is possible for Graph 35+. The rest is quite flicky.
Fourth, we didn't tried the Axe method, but as the screen is "better" than TIs, that can be too flicky to be good. I have to test that.
So... Monochrome is fine too! :p