All of the action takes place on the bottom screen. In order to destroy viruses, you need to touch three viruses, creating a transparent triangle on the play field. Tapping one of the three viruses in the triangle destroys the viruses. Although it may sound easy, the triangle must be formed and deleted quickly, otherwise the viruses crystallize and are rendered useless. However, you can revitalize crystallized viruses by either trapping them within a triangle or destroying it, or by using a pill.
Before destroying the triangle, you can also try and form additional triangles by using active viruses trapped inside the original triangle. In other words, if a green triangle is created, all viruses in the triangle are also activated. If two blue viruses are trapped and activated, touching another blue virus will create another triangle that is linked to the original. Destroying any of these groups will destroy all of them, earning you more points. The downside is that if you can't destroy the groups, all active viruses become useless.
The concept behind Puchi Puchi Virus is a solid one. The mechanics are easy to learn and the game is fun. However, the random tapping loophole does take some of the fun out of the game and indicates a few loose ends in regards to how the gameplay plays out. Still, if you're a puzzle fan and not one to fall back on cheap techniques, Puchi Puchi Virus is worth a look.
