Hey, nice mod! I started a sea block playthrough myself recently and this tool is quite handy. I noticed, that it also selects tiles like landfill though. The best I could come up with to fix this are the following two lines, that you could include in the selection tool prototype:

tile_filters = {"out-of-map"},
alt_tile_filters = {"out-of-map"},

If anyone would have out-of-map tiles they would still be selected, but that seams kind of unlikely ;)

Well, you are right - for some reason i never (even accidentally) selected ground or any tile while testing this and never noticed this behaviour.

Did pretty much the same thing as you, just set the tile filters to tile-unknown instead of out-of-map, which as far as i could find is an 'error' tile, as in if you have it in your map you have other things to worry about. Cant even be placed in editor mode (unlike out-of-map), and I kind of think the out-of-map is used in several mods for 'space', so just in case better not use that one.

So should be fixed in the new version

Thanks! Tile-unknown is a better solution. Nice catch! Will keep it in mind if I ever run into a similar issue.

Its a bit unfortunate that you have options for whitelist or blacklist, but you cant set something like whitelist (with empty table => select nothing) or blacklist (also with empty table => select everything). For some reason its set up that if you have an empty table (or nil), then no matter if you use whitelist or blacklist it allows for selection of everything...

Oh well I guess.