I have noticed a TERRIBLE bug !!!!!!
Sometimes the tile pic on unusable squares does NOT match the planet geograghy ...
( ex: It appears the terrain is desert, but when you click on the tile it is ocean ??? )
This makes the game UNPLAYABLE !!!!
Until this is fixed I am going to uninstall the game and hold my breath !!!!
... or you could hire me at a modest salary to check all the tiles ...