Tiling with Three Polygons Is Undecidable

And then you read the abstract and realize that this is an improvement of an earlier result using five polygons (which in turn built on a history of earlier results).

So, still a great result, but not as out there as one may think.

I think it's also worth pointing out that in theoretical CS and most of math, it is common to list authors alphabetically. I don't think we have a way of knowing the relative contribution of the two authors. Demaine is obviously accomplished, but I find the kind of hero worship found in this thread distasteful and the facts don't support it here. Give credit to Langerman; Demaine surely would!