Reached wave 8, then abandoned the game. Difficulty should increase. I'd like to see maybe some skin around the cells, so you can see where the next wave is coming from, instead of relying on the white cells movement, which feels a bit cheaty. White cells should die after absorbing a number of viruses too. And i'd like to see something that prevents the white cells clumping up too much, i think that would make it more strategic.