The radial movement is a great idea, and brings an interessting challenge. Adds a lot to the concept.
It would be great if the movment could be inversed though.
I don't know if this just happened to me, but i started the game several times to check this out: once you fail and hit Enter to play again, the negativ Shieldscore remained. So the first pathogen to break through would end my game.
And my score (860 pts) was not entered into the list?