there are 3 layers of tiles.
1st is ground, it's where you should, and must, use the little bucket.
each of the layers have it's own er.. layer..
now say you made the first and 2nd layers and on the 3rd you bucket the whole place with say.. a table..
simply choose a white tiles and rebucket it , and start that layer
such as in program like paint, if you use the bucket it will fill up everything it can reach while diffrent colored pixels block it.
so if we have say a table and the rest is grass, it will only bucket effect the grass (assuming you click on a grass spot and not a table spot)
so if say you got:
XXXXX
XTTTX
XXXXX
and you click on a T the Xs will stay the same and all the Ts will be recolored, that what makes this tool very useful.
though if the Xs are on another layer, the entire map will be filled up seeing as there is nothing that can block it.
got it? i am not sure i would but i am talking alot so maybe you can figure out something