Sorry it took me so long to write this!
This game is amazing! I'm a fan of tower defence games and this one has the mechanics well sorted out. I loved having the ability to slow down some of the larger viruses so that I could have more time to take them out, that was a lovely and well balanced mechanic. The tutorial level is a really good tutorial level as well. It doesn't let you get by easily and makes sure you understand the merit of each item.
Overall, I enjoyed this game a lot :)