A fun exercise in 'constrained' writing about a complex topic. However making that claim that it 'explained' Relativity is not valid in any reasonable sense.

I found the reliance on keeping to the 1000 most commonly used words to be actually fairly painful to read thru to the end and even harder to understand.

Perhaps "Relativity as explained to a 6 year old" might make it more accessible. A 6 year old has a vocabulary of ~5000 to 10000 words (for reference) and being able to take these "verbal shortcuts" aka words would make for better understanding.