Can you tell me what the problem is for you when you click the first link? I tried to make it work for all browsers (even mobile, but the UI isn't very mobile friendly), so I would like to get it working on your system too. If you can give me a bug report (and maybe try from different system), that would be great.

The second link explains:

• mutability: https://github.com/bterwijn/memory_graph#mutable-type
• shallow copy: https://github.com/bterwijn/memory_graph#copying-values-of-mutable-type
• difference between x += y and x = x + y: https://github.com/bterwijn/memory_graph#name-rebinding

It's left to the reader to generalize this to x |= y vs x = x | y.