Thanks again for playing!
In the beginning this was planned to be more like a tower defense - you would actually plant the trees (with a limited amount of seeds per round), and each time you have to survive a wave of rain clouds, sun-rays (that potentially can lead to forest fires) and maybe woodchoppers. To emphasize the message of climate change, waves would get crazier and crazier.
So yeah, now it's a relaxed sandbox, but definitely with potential for a puzzle game. I like the idea of forcing certain tiles always being forested. Another idea I just had would be adding huts with little people in it, and those need to be protected from floods.