>>12163479
Not quite; the op image is the actual commercial release of Castle of Illusion for the GG. Some games were released this way early on to put out as much content as possible for the new system, including Olympic Gold, Prince of Persia and maybe a couple dozen others.

>>12163339
The GG screen could actually perform subpixel rendering, so despite the limited native 1:1 resolution of its screen, it could actually render a fair approximation of a larger grid of pixels. While the general approach with dual SMS/GG releases was to develop for the former and then tweak it for the latter, technically they could simply dump literally the same ROM onto a GG cartridge, set a certain pin on the board to flag it as an "SMS mode" game, and the game would work. (Anybody can try that with an emulator if you rename a .sms rom as .gg)

Some optimization was usually welcome, but not even necessary. For Castle of Illusion they simply changed the font to look as legible as possible accounting for how the subpixel rendering would display it, and recolored a couple of sprites (the treasure chests at least iirc) to stand out more; but otherwise it's basically the exact same game.