4. The background color of the globe is now blue (ocean). Even when the globe is completely covered with textured polygons one can sometimes see the backround color at the globe border (screenshot 3). Therefore it would be good if one can change the background color via ruleset.
This is probably necessary for TFTD anyway, where the backround color of the globe is yellow (land masses).
Maybe it would be better to drop the "background" altogether, instead tiling the "leftover" space with a special terrain - one that has a flag "UFOs that crash here are destroyed"? that would eliminate the edge-effects in the geoscape globe.
even better, make that a "terrain type" integer:
standard terrain types would be "0" = "water" and "1" = "land".
shot-down UFOs would be destroyed if over "0" terrain, shot-down flying subs might be destroyed if over "1" terrain...
for special scenarios, you could add a terrain type "2" = "lava", which destroys everything... or a terrain type "3" = "green cheese" for a moon scenario, which reduces the impact damage dealt to UFOs that crash there