Starting Bubbles: 65
Recommended Potions: RB Bubble and the +3 holes in the ceiling
the Charm of Antidote
Points needed for 1, 2, 3 Star:
85 000, 115 000, 140 000
Doom Skull Bubbles
Shoot like a madman to let as many bubbles in the middle with all the doom skulls fall/be burst away. It is quite essential to leave the virus clusters at the sides untouched, as you need the points they will generate falling on Spiders into the Cauldrons.
When you have done all you can in the middle, drop the side virus clusters and burst more bubbles on the sides, to see the ceiling.