The game was quite challenging. Well, that is up until about 81% when I realized that I can upgrade my virus; then it became too easy. It was still fun though. Cheers.
I like the idea. But I must say the game is broken. In games like these, when you're thinking "I hope it works this time" instead of "What can I do to improve this" something is wrong. My bridges will fail one turn, and work the next.