I absolutely love the fact that the OP did not get a domain name for this demo. This is an interesting "technique" I haven't seen for quite a while. People tend to own and re-new tenths of domain names, which are just sitting there for an "just in case" moment. This is a great example of how things can really be simplified - spin up an instance, make a demo, shut the instance down.
The IPs behind my projects have changed dozens of times over the years (new server, changing hosting provider, adding a load balancer, etc.). A simple DNS change allows the same domain name to follow the project.
I'm actually surprised HN permits links to IP addresses. While links posted here are not guaranteed to point to the same content in the future anyway, it is more likely that an IP address will change before the project is taken down entirely. Search engine posterity and all.