I like that it's animated; nearly every static "visual proof" of the Pythagorean theorem is nearly incomprehensible to me without a lot of explanation---I'm a huge fan of visual proofs but for most of them you really need a time dimension to make sense of them.
Another cute way that's more obviously correct without translations is to consider a square with sides of length a+b. You get an interior square of area c^2 and 4 right triangles with legs of size a and b.
Nice animation, but I think in the last step when c² is mentioned (after "a² + b²"), the c-square should be restored such that it is again visible as square.
now let's do this for the rest of the education field!