This game is more frustrating than fun.
Once the game is beaten, the additional levels hold nothing back at the player. At times, about 80% of the screen is filled with antibiotics, making it mandatory to get your immunity up. However, the white blood cells are many, big, and can move about, meaning you need the strength and manpower (viruspower?) to take them down. This is where the issue begins, the antibiotics can make the field impossible at times to even see any white or red bloodcells. Because of the number, white cells can wipe your entire viruses team out the moment they form.
I can take out one with about two or three viruses. But if six viruses form the moment the White cell is over them, they're all gone.
Don't get me wrong, I like the concept of the game, but it can be relentlessly uncaring at times.