Visually simple, but effective. Game play wise it can get a bit dull though, when there is nothing to do for a moment. Also a nice touch that there already runs a simulation in the background of the menu.

(I had to read the other comments to get that you can move the camera with the arrow keys.)

Interesting concept! I would have loved a more in depth tutorial, since it took me a while to figure out that you were supposed to destroy the virus and not run away from it. Once I got a hang of it though, it was very engaging and challenging. 

You could also maybe add an option to move the play area via a mouse button instead of arrow keys to make it more intuitive, but its definitely not a game-breaker.

Nice setup, what about assigning a intruder as target to follow and touch, instead of a position - mostly, the defenders arrive when the intruder has moved elsewhere...

Thumbs up!