Really awesome until the last few levels. Before the later stages, it was relaxing, like playing in a sandbox, yet reasonably challenging without being frustrating or punishing.
Unfortunately, as I got to the later stages, difficulty arose due to a certain totem being placed in a very tricky, high and near-lava location. You have to rely on the individual pathing of the AI, but there's not much indication if they'll be able to get up slopes (when there's multiple potential routes to a location) so trying to get them to this totem without having them try to cross lava is an exercise in frustration. The AI pathing tends to be annoying to deal with as the stages get harder. Also, depending on how you may have tried to build walls in stages with lava, you may find yourself having spent a lot of time on a stage but in a sitation where you'll have to try to destroy some walls to let your villagers get to a totem. Doing this is tedious because you need to use explosive plants (if you made rock walls). I don't understand the point in letting players manipulate something in such a tedious way instead of providing a less time-consuming method.
Overall, dealing with the lava is quite frustrating, especially with how it can completely wipe out villages if so much as a particle touches some of your greenery. I understand having a challenge makes things more fun, but the way this challenge is presented is more frustrating than entertaining, because a small mistake can reset your entire stage progress.
Slight variation on the level design and the lava mechanics would've probably made the game fun, but as it is I can't recommend it because of the unpleasantness of the later levels. Challenge should not come from dealing with the stupid AI, and mistakes shouldn't make you feel like you've just wasted a bunch of time, because that's no fun. Towards the end it just became not pleasant to play anymore. It's a shame because the sandbox mechanics are very entertaining to interact with - it's almost like they weren't sure whether they wanted to frustrate players with hard challenges or provide a relaxing, slow-paced sandbox game.