Excellent! A similar program, apparently from 3 years ago, did similar things, in Basic also, on the Amstrad CPC, a machine with the same processor, a little more RAM and more (27) colors or shades of green, depending on the screen it was hooked to.
The webpage displays the color (left) and green (right) versions on hovering your pointer over the ribbon (above).
Image 1 and 2 are okay in both cases, image 3 is clearly tuned for color screen, image 4 for green screen.
* colored spheres (like you did)
* (one) checkerboard surface
* self-shadowing (like you did)
* cast shadows (like you did)
* partial or total specular reflection!
See https://www.cpc-power.com/index.php?page=detail&num=19283
The webpage displays the color (left) and green (right) versions on hovering your pointer over the ribbon (above). Image 1 and 2 are okay in both cases, image 3 is clearly tuned for color screen, image 4 for green screen.
Or direct links to the relevant variants:
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...
https://www.cpc-power.com/extra_lire_fichier.php?extra=cpcol...