Looks awesome. I tried coding up a multi-agent system for my CS degree and it was incredibly complicated. I was trying to implement an algorithm I found to give each agent emotions of fear, anger, happiness and sadness in order to change their behaviours... it was way more difficult than I expected but you can read more about it here if you're also interested in this stuff. The 3D graphics in this example are way cooler than my 2D shapes.
I read about this a lot a while ago, the main solution I came across was that in the diamond age when we get to that point in societal development. We'll be able to make tiny diamond bubbles with a vacuum inside, and they can be used to create airships and floating platforms. The airship doesn't have to be a single large vacuum diamond hull, but could also be made from many smaller diamonds which would help prevent a catastrophic failure. The diamond bubbles would be strong and light enough to hold the vacuum.
I think the aluminium cans have a thin plastic or polymer coating on the inside too, which stops the drink from tasting like metal... so not sure if it's 100% plastic free either.