You can use several strategies on level 85. One is to get a Lightning power-up. Combo explosions will charge a Lightning in no time, but it might be challenging to make enough of those, as the space is quite limited. You can also get a Lightning by destroying the crates in the right side of the field. It is quite hard to get to the crates so keep both methods in mind and adjust your strategy accordingly!
Another way of getting through this level is by collecting two powerful power-ups. If you are lucky enough, you are not going to need a Lightning at all!