There is another sporadic solution, and the 8 piece solution you've found is not, in fact a sporadic.
And yes, the infinities are uncountable.
There is another sporadic solution, and the 8 piece solution you've found is not, in fact a sporadic.
And yes, the infinities are uncountable.
Oh, right - you can vary the shape of the diagonal lines, provided each "arm" has rotational symmetry about its mid-point.
OK, so we've got three infinite families and the trivial solution (only one piece - is that your sporadic solution?). I think that might be all: each piece can contain 4, 2, 1 or 1/2 of the original square's corners, since (lacuna) all pieces must contain the same number of corners and further subdividing the corners (into 1/3s, say) would mean some pieces don't touch the centre (another lacuna).
More to do, though.
And now do it for an equilateral triangle.
My head hurts.
Half my life is spent helping people discover that they're good at "proper math" even when they think they're bad at "school math."