I figured out I needed to clear the rbc tally before the time ran out on my third game, where I got to level 16 and scored 40685, almost enough for a site high score.
The game ended the same way though, running out of time, even though I killed practically every RBC that arrived, and got the only time-add powerup that arrived. I even most of the invisible RBC's that were inside the anitbody clouds too.
I have suspicions that:
* The game is easier on a slow machine. I've been playing on a slow machine choking on XP
, and with a moderate amount of stuff on-screen, it slows way down. I almost never felt at risk of actually losing all my virus spores, or of missing more than a very few RBCs, mostly the invisible ones.
* Some levels may become impossible by chance.
The two combined make it sort of a tedious endurance/stubbornness test. I don't think there was much if anything I could do better, unless there is some trick to get more RBC's or time extension powerups to show up before the time runs out. Maybe on a faster computer, there are always enough RBC's and/or it gets more challenging to keep the spores alive and catch all the RBC's.
PvK