It is a good idea to memorize the bubbles on your right hand when the game first roll out. You will very likely find yourself in a position when you can use the knowledge of the bubble colours. That is right after bursting your way through the lower section, but not yet revealed any more of level EI 1-7. If you haven’t memorized the bubbles, you can use one of your Rainbow bubbles to drop a big cluster from the wall on a green spider.
Most of the level guides at this site have a video as a complement to the textual guide, level 7 at he first eternal isles section has one as well and here it have an essential role, as you’ll need to see for yourself what I mean with organized luck. In the video (time 1:45) I am shooting a baby blue bubble to drop the ceiling. I got lucky there, but actually luck have not so much to do with clearing as you may think. If I wouldn’t have dropped the ceiling with the blue bubble, I would have dropped it soon enough using a rainbow bubble! The rainbow bubble is actually the main ingredient for success at EI level 1 – 7! I have tried alternate ways of playing this level, but never managed to actually pass for even one Star, those times that I get to see the ceiling before it drops.