Multicolor Chocobos

What's this thing about airship shadow? Never heard of it, possibly a detailed explaination, please

You know, how the airship shadow on the ground while you are flying around has a different size depending on what tile it is over? That shadow becomes slightly larger over mountains, and smaller over oceans/water, and normal size over grass. It sounds like he worked in a check for the event bits that are set depending on which kind of chocobo you are currently using along with the tile properties to check if the vehicle (chocobo) is over grass, mountains, or water, and allow or disallow it to walk over it. Pretty clever stuff!