Animating a Blob of dots to show population density?

I have a 2x2 grid, each representing a different option

I would like to highlight a blob shape of dots (like a moving scattergraph) to show that things move. Like a population density kind of thing.

So to begin with the blob would 100% be in Option A then it would move and be 75% option A and 25 Option B.  Then it would be 50% option A, 35% Option B and 15% Option c and eventually end up 25% Option A, 15% Option B, 30% Option c and 30% Option D.

(I really my maths stands up there)

I really hope that makes sense! Any help would be much appreciated.

Thanks in advance!