good idea but needs a lot more work. those bubbles look a bit dull over time and every level is exactly the same. how about doing actual levels like you're in a vein (like a race with force of the bloodstream) or organ with different background and large cells as level borders? you need to give the player some kind of visual feedback of which cells he can consume and which not. i keep running into clearly smaller cells receiving damage...
immune biology is extremely interesting and offers enough cool stuff to put into a game. white cells as white blobs? oh come on! how about tricking T-helper cells, escaping macrophages or infecting B-cells to temporarily stun the production of anti-body which slow you down? or avoiding AoE-damage from T-Killer cells?
think of something! this is boring as it is atm.