Hello!
First off, awesome game! I love puzzle games like this and I've done a bit of virology in my day so its already a cult game for me.
Second, I want to let you know I am a consumer. I'm not a dev or an artist, but I have been part of the indie dev process before and understand a bit more - though that maybe dangerous
Ok, onto the game:
Art - so cute!! I love the cartoon/Nickelodeon style! Awesome!! title font is fantastic!!
UI - I don't like the buttons on the menu screen, but that is the smallest detail. They seem a bit out of place with the rest of the art. Maybe its the font on the buttons??
- I somehow clicked too soon and missed the "How to play" but then went back to your post and realized you may not have it in the game?? Anyways, maybe include a "how to" link on the main menu
Gameplay - loved it! Its hard to get the hang of at first and I love that! However, it does get a bit repeatitive. It would be awesome to include other viruses or "power ups" for your bubbles. Perhaps you could unlock other bubbles as you unlock other levels? You could have anything! Like, incinerate bubbles (burn the virus but also pops your other bubbles) or bubbles with anti-viral drugs in them and then you could also have Resistant viruses!
Its a great game and so many fun things you could do with it! Best of luck!!