I thought it would be nice if you push something floating on water it would move in the stream. The movement was random, but then I realized it's silly. Of course rivers must have a direction where they flow, so it was something I added today. This feature was kind of easy to add. I just created four river tiles each with direction of flow and re-factored river creation which already had an orientation (horizontal or vertical) and direction where it was flowing.
I tried to test it with a barrel, but it didn't go into water. Sadly I had removed that feature for now, because I'm having difficulties with the terrain and object interations. But in theory it works and you can push stuff into river and watch it go downriver.
Another feature I still need to implement is a temperature map. I realized that if I have temperature it needs to be local and not in level scope. It would be funny to walk on lava in snowy mountain and still feel cold. Temperature map is going to have mixing between temperatures so near lava it's beginning to be hot and it could even melt snow and stuff like that. It's a good preparation for level events like lava eruptions.