Various placeable waters. Very configurable.
Providing the player with new tools or adjusting the game interface, without fundamentally changing gameplay.
Does Factorio modding API allow to plug something in into "undo" functionality?
What do you think about allowing to undo placement of waterfill, that would place ghost landfill over it?
Sounds like a good idea ... I'll have to look into that when I have some more time ;)
hm looks like it is currently not possible to achieve this easily.