Interesting web finds

[Renegade 13]

I also made it to about 14 or so, then ran out of time

[Suicide Junkie]

You've gotta kill X number of cells before the time runs out.

The viruses are pretty lame, what with the complete inability to infect things without your direct intervention.
I have no idea why that's not one of the available upgrades, even if it were just a tiny percentage chance like the immunity.

[Arkcon]

The biohazard powerup causes that. But it just lets you kill cells, the infected cell doesn't release new viruses. So its a poor simulation of virus action. But anyway, its just a "catch the falling object" game, played upwards instead of downwards, with moving obstacles.

A tip I've heard, but haven't really exploited, is to wait with one rbc left, to see if you can score more powerups. Upgrades become very expensive after 4 level.

I'm gonna go play now. This game is addictive.