my world has humanoid alien natives living on floating rainforests. What kind advanced tech could they create?
You should look into biopunk/hopepunk/solarpunk for some cool eco/nature-friendly tech ideas.
They could theoretically have all we have and then some, assuming they have access to the same resources (even if imported).
You should definitely look into sustainable technologies. If their homeland is still largely/entirely rainforest (rather than being destroyed by deforestation), that shows they respect and value the environment. It would be likely they’ve been focused on developing in as eco-friendly a way as possible throughout much, if not all, of their history (and that includes not chopping down their rainforest to make room for farmlands!). Clean, renewable energy is a definite and probably has been their primary source(s) of energy throughout history. On the other hand, large industrial complexes which pollute and require clearing precious forest lands to build would likely have been built elsewhere if possible, or not at all. Industry would probably exist on a much smaller scale than we modern-day humans are used to.
By floating, do you mean like sky-islands? If so, I could definitely envision flight being important to them as soon as their technology allowed for it. By the time their society is at a modern or post-modern tech level, their flying vehicles (planes, flying cars?, etc.) are probably far more advanced than ours. That they’d have spaceplanes (airplanes that double as spacecraft) already is a given.
It’s possible that they could modernize and industrialize on a similar (or even greater) scale to us and solve their need for land/building space without resorting to deforestation by building floating (mega)structures. These structures could house their factories, agricultural complexes, corporations, etc. that support a modernized people. I don’t know how you could realistically explain floating buildings/megastructures, but you could always say they’re held up by whatever phenomenon holds up the islands.
Of course, if they’re building floating buildings, they need some way to transport the materials there. Flying construction vehicles? Seems like a definite possibility.
If they have any reason to believe their rainforests are threatened (e.g., by climate change), bioengineering would be a big field for them. After all, if they care deeply about the environment, then it follows that they would not only want to protect it but also want to reverse damage that has been done --and possibly even (if there’s no taboo against tampering with Mother Nature) genetically engineer species for better survival. (The latter is not just limited to “their ecosystem is threatened”. For instance, if a particular species is threatened by disease, they may genetically engineer them to have immunity to it as part of their conservation efforts.)
That was mostly just drivel but hopefully something in their answers your question.
yes they have sky islands. They can fly them selves a the islands are still rainforest. They are bit primitive so they don’t flying cars .They do have flying chariots pulled by dragons or air ships.